mesh_bsurfaces.py

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#
#  This program is free software; you can redistribute it and/or
#  modify it under the terms of the GNU General Public License
#  as published by the Free Software Foundation; version 2
#  of the License.
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#  but WITHOUT ANY WARRANTY; without even the implied warranty of
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bl_info = {
    "name": "Bsurfaces GPL Edition",
    "author": "Eclectiel",
    "version": (1, 5),
    "blender": (2, 76, 0),
    "location": "View3D > EditMode > ToolShelf",
    "description": "Modeling and retopology tool.",
    "wiki_url": "http:https://wiki.blender.org/index.php/Dev:Ref/Release_Notes/2.64/Bsurfaces_1.5",
    "category": "Mesh",
}


import bpy
import bmesh
import math
import mathutils
import operator

from math import *




class VIEW3D_PT_tools_SURFSK_mesh(bpy.types.Panel):
    bl_space_type = 'VIEW_3D'
    bl_region_type = 'TOOLS'
    bl_category = 'Tools'
    bl_context = "mesh_edit"
    bl_label = "Bsurfaces"

    @classmethod
    def poll(cls, context):
        return context.active_object


    def draw(self, context):
        layout = self.layout

        scn = context.scene
        ob = context.object

        col = layout.column(align=True)
        row = layout.row()
        row.separator()
        col.operator("gpencil.surfsk_add_surface", text="Add Surface")
        col.operator("gpencil.surfsk_edit_strokes", text="Edit Strokes")
        col.prop(scn, "SURFSK_cyclic_cross")
        col.prop(scn, "SURFSK_cyclic_follow")
        col.prop(scn, "SURFSK_loops_on_strokes")
        col.prop(scn, "SURFSK_automatic_join")
        col.prop(scn, "SURFSK_keep_strokes")



class VIEW3D_PT_tools_SURFSK_curve(bpy.types.Panel):
    bl_space_type = 'VIEW_3D'
    bl_region_type = 'TOOLS'
    bl_context = "curve_edit"
    bl_category = 'Tools'
    bl_label = "Bsurfaces"

    @classmethod
    def poll(cls, context):
        return context.active_object


    def draw(self, context):
        layout = self.layout

        scn = context.scene
        ob = context.object

        col = layout.column(align=True)
        row = layout.row()
        row.separator()
        col.operator("curve.surfsk_first_points", text="Set First Points")
        col.operator("curve.switch_direction", text="Switch Direction")
        col.operator("curve.surfsk_reorder_splines", text="Reorder Splines")




#### Returns the type of strokes used.
def get_strokes_type(main_object):
    strokes_type = ""
    strokes_num = 0

    # Check if they are grease pencil
    try:
        #### Get the active grease pencil layer.
        strokes_num = len(main_object.grease_pencil.layers.active.active_frame.strokes)

        if strokes_num > 0:
            strokes_type = "GP_STROKES"
    except:
        pass


    # Check if they are curves, if there aren't grease pencil strokes.
    if strokes_type == "":
        if len(bpy.context.selected_objects) == 2:
            for ob in bpy.context.selected_objects:
                if ob != bpy.context.scene.objects.active and ob.type == "CURVE":
                    strokes_type = "EXTERNAL_CURVE"
                    strokes_num = len(ob.data.splines)

                    # Check if there is any non-bezier spline.
                    for i in range(len(ob.data.splines)):
                        if ob.data.splines[i].type != "BEZIER":
                            strokes_type = "CURVE_WITH_NON_BEZIER_SPLINES"
                            break

                elif ob != bpy.context.scene.objects.active and ob.type != "CURVE":
                    strokes_type = "EXTERNAL_NO_CURVE"
        elif len(bpy.context.selected_objects) > 2:
            strokes_type = "MORE_THAN_ONE_EXTERNAL"


    # Check if there is a single stroke without any selection in the object.
    if strokes_num == 1 and main_object.data.total_vert_sel == 0:
        if strokes_type == "EXTERNAL_CURVE":
            strokes_type = "SINGLE_CURVE_STROKE_NO_SELECTION"
        elif strokes_type == "GP_STROKES":
            strokes_type = "SINGLE_GP_STROKE_NO_SELECTION"

    if strokes_num == 0 and main_object.data.total_vert_sel > 0:
        strokes_type = "SELECTION_ALONE"


    if strokes_type == "":
        strokes_type = "NO_STROKES"



    return strokes_type




# Surface generator operator.
class GPENCIL_OT_SURFSK_add_surface(bpy.types.Operator):
    bl_idname = "gpencil.surfsk_add_surface"
    bl_label = "Bsurfaces add surface"
    bl_description = "Generates surfaces from grease pencil strokes, bezier curves or loose edges"
    bl_options = {'REGISTER', 'UNDO'}


    edges_U = bpy.props.IntProperty(name = "Cross",
                        description = "Number of face-loops crossing the strokes",
                        default = 1,
                        min = 1,
                        max = 200)

    edges_V = bpy.props.IntProperty(name = "Follow",
                        description = "Number of face-loops following the strokes",
                        default = 1,
                        min = 1,
                        max = 200)

    cyclic_cross = bpy.props.BoolProperty(name = "Cyclic Cross",
                        description = "Make cyclic the face-loops crossing the strokes",
                        default = False)

    cyclic_follow = bpy.props.BoolProperty(name = "Cyclic Follow",
                        description = "Make cyclic the face-loops following the strokes",
                        default = False)

    loops_on_strokes = bpy.props.BoolProperty(name = "Loops on strokes",
                        description = "Make the loops match the paths of the strokes",
                        default = False)

    automatic_join = bpy.props.BoolProperty(name = "Automatic join",
                        description = "Join automatically vertices of either surfaces generated by crosshatching, or from the borders of closed shapes",
                        default = False)

    join_stretch_factor = bpy.props.FloatProperty(name = "Stretch",
                        description = "Amount of stretching or shrinking allowed for edges when joining vertices automatically",
                        default = 1,
                        min = 0,
                        max = 3,
                        subtype = 'FACTOR')




    def draw(self, context):
        layout = self.layout

        scn = context.scene
        ob = context.object

        col = layout.column(align=True)
        row = layout.row()

        if not self.is_fill_faces:
            row.separator()
            if not self.is_crosshatch:
                if not self.selection_U_exists:
                    col.prop(self, "edges_U")
                    row.separator()

                if not self.selection_V_exists:
                    col.prop(self, "edges_V")
                    row.separator()

                row.separator()

                if not self.selection_U_exists:
                    if not ((self.selection_V_exists and not self.selection_V_is_closed) or (self.selection_V2_exists and not self.selection_V2_is_closed)):
                        col.prop(self, "cyclic_cross")

                if not self.selection_V_exists:
                    if not ((self.selection_U_exists and not self.selection_U_is_closed) or (self.selection_U2_exists and not self.selection_U2_is_closed)):
                        col.prop(self, "cyclic_follow")


                col.prop(self, "loops_on_strokes")

            col.prop(self, "automatic_join")

            if self.automatic_join:
                row.separator()
                col.separator()
                row.separator()
                col.prop(self, "join_stretch_factor")



    #### Get an ordered list of a chain of vertices.
    def get_ordered_verts(self, ob, all_selected_edges_idx, all_selected_verts_idx, first_vert_idx, middle_vertex_idx, closing_vert_idx):
        # Order selected vertices.
        verts_ordered = []
        if closing_vert_idx != None:
            verts_ordered.append(ob.data.vertices[closing_vert_idx])

        verts_ordered.append(ob.data.vertices[first_vert_idx])
        prev_v = first_vert_idx
        prev_ed = None
        finish_while = False
        while True:
            edges_non_matched = 0
            for i in all_selected_edges_idx:
                if ob.data.edges[i] != prev_ed and ob.data.edges[i].vertices[0] == prev_v and ob.data.edges[i].vertices[1] in all_selected_verts_idx:
                    verts_ordered.append(ob.data.vertices[ob.data.edges[i].vertices[1]])
                    prev_v = ob.data.edges[i].vertices[1]
                    prev_ed = ob.data.edges[i]
                elif ob.data.edges[i] != prev_ed and ob.data.edges[i].vertices[1] == prev_v and ob.data.edges[i].vertices[0] in all_selected_verts_idx:
                    verts_ordered.append(ob.data.vertices[ob.data.edges[i].vertices[0]])
                    prev_v = ob.data.edges[i].vertices[0]
                    prev_ed = ob.data.edges[i]
                else:
                    edges_non_matched += 1

                    if edges_non_matched == len(all_selected_edges_idx):
                        finish_while = True

            if finish_while:
                break

        if closing_vert_idx != None:
            verts_ordered.append(ob.data.vertices[closing_vert_idx])

        if middle_vertex_idx != None:
            verts_ordered.append(ob.data.vertices[middle_vertex_idx])
            verts_ordered.reverse()

        return tuple(verts_ordered)


    #### Calculates length of a chain of points.
    def get_chain_length(self, object, verts_ordered):
        matrix = object.matrix_world

        edges_lengths = []
        edges_lengths_sum = 0
        for i in range(0, len(verts_ordered)):
            if i == 0:
                prev_v_co = matrix * verts_ordered[i].co
            else:
                v_co = matrix * verts_ordered[i].co

                v_difs = [prev_v_co[0] - v_co[0], prev_v_co[1] - v_co[1], prev_v_co[2] - v_co[2]]
                edge_length = abs(sqrt(v_difs[0] * v_difs[0] + v_difs[1] * v_difs[1] + v_difs[2] * v_difs[2]))

                edges_lengths.append(edge_length)
                edges_lengths_sum += edge_length

                prev_v_co = v_co

        return edges_lengths, edges_lengths_sum


    #### Calculates the proportion of the edges of a chain of edges, relative to the full chain length.
    def get_edges_proportions(self, edges_lengths, edges_lengths_sum, use_boundaries, fixed_edges_num):
        edges_proportions = []
        if use_boundaries:
            verts_count = 1
            for l in edges_lengths:
                edges_proportions.append(l / edges_lengths_sum)
                verts_count += 1
        else:
            verts_count = 1
            for n in range(0, fixed_edges_num):
                edges_proportions.append(1 / fixed_edges_num)
                verts_count += 1

        return edges_proportions


    #### Calculates the angle between two pairs of points in space.
    def orientation_difference(self, points_A_co, points_B_co): # each parameter should be a list with two elements, and each element should be a x,y,z coordinate.
        vec_A = points_A_co[0] - points_A_co[1]
        vec_B = points_B_co[0] - points_B_co[1]

        angle = vec_A.angle(vec_B)

        if angle > 0.5 * math.pi:
            angle = abs(angle - math.pi)

        return angle



    #### Calculate the which vert of verts_idx list is the nearest one to the point_co coordinates, and the distance.
    def shortest_distance(self, object, point_co, verts_idx):
        matrix = object.matrix_world

        for i in range(0, len(verts_idx)):
            dist = (point_co - matrix * object.data.vertices[verts_idx[i]].co).length
            if i == 0:
                prev_dist = dist
                nearest_vert_idx = verts_idx[i]
                shortest_dist = dist

            if dist < prev_dist:
                prev_dist = dist
                nearest_vert_idx = verts_idx[i]
                shortest_dist = dist

        return nearest_vert_idx, shortest_dist


    #### Returns the index of the opposite vert tip in a chain, given a vert tip index as parameter, and a multidimentional list with all pairs of tips.
    def opposite_tip(self, vert_tip_idx, all_chains_tips_idx):
        opposite_vert_tip_idx = None
        for i in range(0, len(all_chains_tips_idx)):
            if vert_tip_idx == all_chains_tips_idx[i][0]:
                opposite_vert_tip_idx = all_chains_tips_idx[i][1]
            if vert_tip_idx == all_chains_tips_idx[i][1]:
                opposite_vert_tip_idx = all_chains_tips_idx[i][0]

        return opposite_vert_tip_idx



    #### Simplifies a spline and returns the new points coordinates.
    def simplify_spline(self, spline_coords, segments_num):
        simplified_spline = []
        points_between_segments = round(len(spline_coords) / segments_num)

        simplified_spline.append(spline_coords[0])
        for i in range(1, segments_num):
            simplified_spline.append(spline_coords[i * points_between_segments])

        simplified_spline.append(spline_coords[len(spline_coords) - 1])

        return simplified_spline



    #### Cleans up the scene and gets it the same it was at the beginning, in case the script is interrupted in the middle of the execution.
    def cleanup_on_interruption(self):
        # If the original strokes curve comes from conversion from grease pencil and wasn't made by hand, delete it.
        if not self.using_external_curves:
            try:
                bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
                bpy.data.objects[self.original_curve.name].select = True
                bpy.context.scene.objects.active = bpy.data.objects[self.original_curve.name]

                bpy.ops.object.delete()
            except:
                pass

            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.data.objects[self.main_object.name].select = True
            bpy.context.scene.objects.active = bpy.data.objects[self.main_object.name]
        else:
            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.data.objects[self.original_curve.name].select = True
            bpy.data.objects[self.main_object.name].select = True
            bpy.context.scene.objects.active = bpy.data.objects[self.main_object.name]

        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')



    #### Returns a list with the coords of the points distributed over the splines passed to this method according to the proportions parameter.
    def distribute_pts(self, surface_splines, proportions):
        # Calculate the length of each final surface spline.
        surface_splines_lengths = []
        surface_splines_parsed = []
        for sp_idx in range(0, len(surface_splines)):
            # Calculate spline length
            surface_splines_lengths.append(0)
            for i in range(0, len(surface_splines[sp_idx].bezier_points)):
                if i == 0:
                    prev_p = surface_splines[sp_idx].bezier_points[i]
                else:
                    p = surface_splines[sp_idx].bezier_points[i]

                    edge_length = (prev_p.co - p.co).length

                    surface_splines_lengths[sp_idx] += edge_length

                    prev_p = p


        # Calculate vertex positions with appropriate edge proportions, and ordered, for each spline.
        for sp_idx in range(0, len(surface_splines)):
            surface_splines_parsed.append([])
            surface_splines_parsed[sp_idx].append(surface_splines[sp_idx].bezier_points[0].co)

            prev_p_co = surface_splines[sp_idx].bezier_points[0].co
            p_idx = 0
            for prop_idx in range(len(proportions) - 1):
                target_length = surface_splines_lengths[sp_idx] * proportions[prop_idx]

                partial_segment_length = 0


                finish_while = False
                while True:
                    p_co = surface_splines[sp_idx].bezier_points[p_idx].co

                    new_dist = (prev_p_co - p_co).length

                    potential_segment_length = partial_segment_length + new_dist # The new distance that could have the partial segment if it is still shorter than the target length.


                    if potential_segment_length < target_length: # If the potential is still shorter, keep adding.
                        partial_segment_length = potential_segment_length

                        p_idx += 1
                        prev_p_co = p_co

                    elif potential_segment_length > target_length: # If the potential is longer than the target, calculate the target (a point between the last two points), and assign.
                        remaining_dist = target_length - partial_segment_length
                        vec = p_co - prev_p_co
                        vec.normalize()
                        intermediate_co = prev_p_co + (vec * remaining_dist)

                        surface_splines_parsed[sp_idx].append(intermediate_co)

                        partial_segment_length += remaining_dist
                        prev_p_co = intermediate_co

                        finish_while = True

                    elif potential_segment_length == target_length: # If the potential is equal to the target, assign.
                        surface_splines_parsed[sp_idx].append(p_co)

                        prev_p_co = p_co

                        finish_while = True

                    if finish_while:
                        break

            # last point of the spline
            surface_splines_parsed[sp_idx].append(surface_splines[sp_idx].bezier_points[len(surface_splines[sp_idx].bezier_points) - 1].co)


        return surface_splines_parsed



    #### Counts the number of faces that belong to each edge.
    def edge_face_count(self, ob):
        ed_keys_count_dict = {}

        for face in ob.data.polygons:
            for ed_keys in face.edge_keys:
                if not ed_keys in ed_keys_count_dict:
                    ed_keys_count_dict[ed_keys] = 1
                else:
                    ed_keys_count_dict[ed_keys] += 1


        edge_face_count = []
        for i in range(len(ob.data.edges)):
            edge_face_count.append(0)

        for i in range(len(ob.data.edges)):
            ed = ob.data.edges[i]

            v1 = ed.vertices[0]
            v2 = ed.vertices[1]

            if (v1, v2) in ed_keys_count_dict:
                edge_face_count[i] = ed_keys_count_dict[(v1, v2)]
            elif (v2, v1) in ed_keys_count_dict:
                edge_face_count[i] = ed_keys_count_dict[(v2, v1)]


        return edge_face_count



    #### Fills with faces all the selected vertices which form empty triangles or quads.
    def fill_with_faces(self, object):
        all_selected_verts_count = self.main_object_selected_verts_count


        bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='OBJECT')

        #### Calculate average length of selected edges.
        all_selected_verts = []
        original_sel_edges_count = 0
        for ed in object.data.edges:
            if object.data.vertices[ed.vertices[0]].select and object.data.vertices[ed.vertices[1]].select:
                coords = []
                coords.append(object.data.vertices[ed.vertices[0]].co)
                coords.append(object.data.vertices[ed.vertices[1]].co)

                original_sel_edges_count += 1

                if not ed.vertices[0] in all_selected_verts:
                    all_selected_verts.append(ed.vertices[0])

                if not ed.vertices[1] in all_selected_verts:
                    all_selected_verts.append(ed.vertices[1])


        tuple(all_selected_verts)


        #### Check if there is any edge selected. If not, interrupt the script.
        if original_sel_edges_count == 0 and all_selected_verts_count > 0:
            return 0



        #### Get all edges connected to selected verts.
        all_edges_around_sel_verts = []
        edges_connected_to_sel_verts = {}
        verts_connected_to_every_vert = {}
        for ed_idx in range(len(object.data.edges)):
            ed = object.data.edges[ed_idx]
            include_edge = False

            if ed.vertices[0] in all_selected_verts:
                if not ed.vertices[0] in edges_connected_to_sel_verts:
                    edges_connected_to_sel_verts[ed.vertices[0]] = []

                edges_connected_to_sel_verts[ed.vertices[0]].append(ed_idx)
                include_edge = True

            if ed.vertices[1] in all_selected_verts:
                if not ed.vertices[1] in edges_connected_to_sel_verts:
                    edges_connected_to_sel_verts[ed.vertices[1]] = []

                edges_connected_to_sel_verts[ed.vertices[1]].append(ed_idx)
                include_edge = True


            if include_edge == True:
                all_edges_around_sel_verts.append(ed_idx)


            # Get all connected verts to each vert.
            if not ed.vertices[0] in verts_connected_to_every_vert:
                verts_connected_to_every_vert[ed.vertices[0]] = []

            if not ed.vertices[1] in verts_connected_to_every_vert:
                verts_connected_to_every_vert[ed.vertices[1]] = []

            verts_connected_to_every_vert[ed.vertices[0]].append(ed.vertices[1])
            verts_connected_to_every_vert[ed.vertices[1]].append(ed.vertices[0])




        #### Get all verts connected to faces.
        all_verts_part_of_faces = []
        all_edges_faces_count = []
        all_edges_faces_count += self.edge_face_count(object)

        # Get only the selected edges that have faces attached.
        count_faces_of_edges_around_sel_verts = {}
        selected_verts_with_faces = []
        for ed_idx in all_edges_around_sel_verts:
            count_faces_of_edges_around_sel_verts[ed_idx] = all_edges_faces_count[ed_idx]

            if all_edges_faces_count[ed_idx] > 0:
                ed = object.data.edges[ed_idx]

                if not ed.vertices[0] in selected_verts_with_faces:
                    selected_verts_with_faces.append(ed.vertices[0])

                if not ed.vertices[1] in selected_verts_with_faces:
                    selected_verts_with_faces.append(ed.vertices[1])

                all_verts_part_of_faces.append(ed.vertices[0])
                all_verts_part_of_faces.append(ed.vertices[1])

        tuple(selected_verts_with_faces)



        #### Discard unneeded verts from calculations.
        participating_verts = []
        movable_verts = []
        for v_idx in all_selected_verts:
            vert_has_edges_with_one_face = False

            for ed_idx in edges_connected_to_sel_verts[v_idx]: # Check if the actual vert has at least one edge connected to only one face.
                if count_faces_of_edges_around_sel_verts[ed_idx] == 1:
                    vert_has_edges_with_one_face = True

            # If the vert has two or less edges connected and the vert is not part of any face. Or the vert is part of any face and at least one of the connected edges has only one face attached to it.
            if (len(edges_connected_to_sel_verts[v_idx]) == 2 and not v_idx in all_verts_part_of_faces) or len(edges_connected_to_sel_verts[v_idx]) == 1 or (v_idx in all_verts_part_of_faces and vert_has_edges_with_one_face):
                participating_verts.append(v_idx)

                if not v_idx in all_verts_part_of_faces:
                    movable_verts.append(v_idx)



        #### Remove from movable verts list those that are part of closed geometry (ie: triangles, quads)
        for mv_idx in movable_verts:
            freeze_vert = False
            mv_connected_verts = verts_connected_to_every_vert[mv_idx]

            for actual_v_idx in all_selected_verts:
                count_shared_neighbors = 0
                checked_verts = []

                for mv_conn_v_idx in mv_connected_verts:
                    if mv_idx != actual_v_idx:
                        if mv_conn_v_idx in verts_connected_to_every_vert[actual_v_idx] and not mv_conn_v_idx in checked_verts:
                            count_shared_neighbors += 1
                            checked_verts.append(mv_conn_v_idx)


                            if actual_v_idx in mv_connected_verts:
                                freeze_vert = True
                                break

                        if count_shared_neighbors == 2:
                            freeze_vert = True
                            break

                if freeze_vert:
                    break

            if freeze_vert:
                movable_verts.remove(mv_idx)



        #### Calculate merge distance for participating verts.
        shortest_edge_length = None
        for ed in object.data.edges:
            if ed.vertices[0] in movable_verts and ed.vertices[1] in movable_verts:
                v1 = object.data.vertices[ed.vertices[0]]
                v2 = object.data.vertices[ed.vertices[1]]

                length = (v1.co - v2.co).length

                if shortest_edge_length == None:
                    shortest_edge_length = length
                else:
                    if length < shortest_edge_length:
                        shortest_edge_length = length

        if shortest_edge_length != None:
            edges_merge_distance = shortest_edge_length * 0.5
        else:
            edges_merge_distance = 0




        #### Get together the verts near enough. They will be merged later.
        remaining_verts = []
        remaining_verts += participating_verts
        for v1_idx in participating_verts:
            if v1_idx in remaining_verts and v1_idx in movable_verts:
                verts_to_merge = []
                coords_verts_to_merge = {}

                verts_to_merge.append(v1_idx)

                v1_co = object.data.vertices[v1_idx].co
                coords_verts_to_merge[v1_idx] = (v1_co[0], v1_co[1], v1_co[2])


                for v2_idx in remaining_verts:
                    if v1_idx != v2_idx:
                        v2_co = object.data.vertices[v2_idx].co

                        dist = (v1_co - v2_co).length

                        if dist <= edges_merge_distance: # Add the verts which are near enough.
                            verts_to_merge.append(v2_idx)

                            coords_verts_to_merge[v2_idx] = (v2_co[0], v2_co[1], v2_co[2])


                for vm_idx in verts_to_merge:
                    remaining_verts.remove(vm_idx)


                if len(verts_to_merge) > 1:
                    # Calculate middle point of the verts to merge.
                    sum_x_co = 0
                    sum_y_co = 0
                    sum_z_co = 0
                    movable_verts_to_merge_count = 0
                    for i in range(len(verts_to_merge)):
                        if verts_to_merge[i] in movable_verts:
                            v_co = object.data.vertices[verts_to_merge[i]].co

                            sum_x_co += v_co[0]
                            sum_y_co += v_co[1]
                            sum_z_co += v_co[2]

                            movable_verts_to_merge_count += 1

                    middle_point_co = [sum_x_co / movable_verts_to_merge_count, sum_y_co / movable_verts_to_merge_count, sum_z_co / movable_verts_to_merge_count]


                    # Check if any vert to be merged is not movable.
                    shortest_dist = None
                    are_verts_not_movable = False
                    verts_not_movable = []
                    for v_merge_idx in verts_to_merge:
                        if v_merge_idx in participating_verts and not v_merge_idx in movable_verts:
                            are_verts_not_movable = True
                            verts_not_movable.append(v_merge_idx)

                    if are_verts_not_movable:
                        # Get the vert connected to faces, that is nearest to the middle point of the movable verts.
                        shortest_dist = None
                        for vcf_idx in verts_not_movable:
                                dist = abs((object.data.vertices[vcf_idx].co - mathutils.Vector(middle_point_co)).length)

                                if shortest_dist == None:
                                    shortest_dist = dist
                                    nearest_vert_idx = vcf_idx
                                else:
                                    if dist < shortest_dist:
                                        shortest_dist = dist
                                        nearest_vert_idx = vcf_idx

                        coords = object.data.vertices[nearest_vert_idx].co
                        target_point_co = [coords[0], coords[1], coords[2]]
                    else:
                         target_point_co = middle_point_co


                    # Move verts to merge to the middle position.
                    for v_merge_idx in verts_to_merge:
                        if v_merge_idx in movable_verts: # Only move the verts that are not part of faces.
                            object.data.vertices[v_merge_idx].co[0] = target_point_co[0]
                            object.data.vertices[v_merge_idx].co[1] = target_point_co[1]
                            object.data.vertices[v_merge_idx].co[2] = target_point_co[2]



        #### Perform "Remove Doubles" to weld all the disconnected verts
        bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='EDIT')
        bpy.ops.mesh.remove_doubles(threshold=0.0001)

        bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='OBJECT')


        #### Get all the definitive selected edges, after weldding.
        selected_edges = []
        edges_per_vert = {} # Number of faces of each selected edge.
        for ed in object.data.edges:
            if object.data.vertices[ed.vertices[0]].select and object.data.vertices[ed.vertices[1]].select:
                selected_edges.append(ed.index)

                # Save all the edges that belong to each vertex.
                if not ed.vertices[0] in edges_per_vert:
                    edges_per_vert[ed.vertices[0]] = []

                if not ed.vertices[1] in edges_per_vert:
                    edges_per_vert[ed.vertices[1]] = []

                edges_per_vert[ed.vertices[0]].append(ed.index)
                edges_per_vert[ed.vertices[1]].append(ed.index)

        # Check if all the edges connected to each vert have two faces attached to them. To discard them later and make calculations faster.
        a = []
        a += self.edge_face_count(object)
        tuple(a)
        verts_surrounded_by_faces = {}
        for v_idx in edges_per_vert:
            edges = edges_per_vert[v_idx]

            edges_with_two_faces_count = 0
            for ed_idx in edges_per_vert[v_idx]:
                if a[ed_idx] == 2:
                    edges_with_two_faces_count += 1

            if edges_with_two_faces_count == len(edges_per_vert[v_idx]):
                verts_surrounded_by_faces[v_idx] = True
            else:
                verts_surrounded_by_faces[v_idx] = False


        #### Get all the selected vertices.
        selected_verts_idx = []
        for v in object.data.vertices:
            if v.select:
                selected_verts_idx.append(v.index)


        #### Get all the faces of the object.
        all_object_faces_verts_idx = []
        for face in object.data.polygons:
            face_verts = []
            face_verts.append(face.vertices[0])
            face_verts.append(face.vertices[1])
            face_verts.append(face.vertices[2])

            if len(face.vertices) == 4:
                face_verts.append(face.vertices[3])

            all_object_faces_verts_idx.append(face_verts)


        #### Deselect all vertices.
        bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='EDIT')
        bpy.ops.mesh.select_all('INVOKE_REGION_WIN', action='DESELECT')
        bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='OBJECT')



        #### Make a dictionary with the verts related to each vert.
        related_key_verts = {}
        for ed_idx in selected_edges:
            ed = object.data.edges[ed_idx]

            if not verts_surrounded_by_faces[ed.vertices[0]]:
                if not ed.vertices[0] in related_key_verts:
                    related_key_verts[ed.vertices[0]] = []

                if not ed.vertices[1] in related_key_verts[ed.vertices[0]]:
                    related_key_verts[ed.vertices[0]].append(ed.vertices[1])

            if not verts_surrounded_by_faces[ed.vertices[1]]:
                if not ed.vertices[1] in related_key_verts:
                    related_key_verts[ed.vertices[1]] = []

                if not ed.vertices[0] in related_key_verts[ed.vertices[1]]:
                    related_key_verts[ed.vertices[1]].append(ed.vertices[0])



        #### Get groups of verts forming each face.
        faces_verts_idx = []
        for v1 in related_key_verts: # verts-1 ....
            for v2 in related_key_verts: # verts-2
                if v1 != v2:
                    related_verts_in_common = []
                    v2_in_rel_v1 = False
                    v1_in_rel_v2 = False
                    for rel_v1 in related_key_verts[v1]:
                        if rel_v1 in related_key_verts[v2]: # Check if related verts of verts-1 are related verts of verts-2.
                            related_verts_in_common.append(rel_v1)

                    if v2 in related_key_verts[v1]:
                        v2_in_rel_v1 = True

                    if v1 in related_key_verts[v2]:
                        v1_in_rel_v2 = True


                    repeated_face = False
                    # If two verts have two related verts in common, they form a quad.
                    if len(related_verts_in_common) == 2:
                        # Check if the face is already saved.
                        all_faces_to_check_idx = faces_verts_idx + all_object_faces_verts_idx


                        for f_verts in all_faces_to_check_idx:
                            repeated_verts = 0

                            if len(f_verts) == 4:
                                if v1 in f_verts: repeated_verts += 1
                                if v2 in f_verts: repeated_verts += 1
                                if related_verts_in_common[0] in f_verts: repeated_verts += 1
                                if related_verts_in_common[1] in f_verts: repeated_verts += 1

                                if repeated_verts == len(f_verts):
                                    repeated_face = True
                                    break

                        if not repeated_face:
                            faces_verts_idx.append([v1, related_verts_in_common[0], v2, related_verts_in_common[1]])

                    elif v2_in_rel_v1 and v1_in_rel_v2 and len(related_verts_in_common) == 1: # If Two verts have one related vert in common and they are related to each other, they form a triangle.
                        # Check if the face is already saved.
                        all_faces_to_check_idx = faces_verts_idx + all_object_faces_verts_idx

                        for f_verts in all_faces_to_check_idx:
                            repeated_verts = 0

                            if len(f_verts) == 3:
                                if v1 in f_verts: repeated_verts += 1
                                if v2 in f_verts: repeated_verts += 1
                                if related_verts_in_common[0] in f_verts: repeated_verts += 1

                                if repeated_verts == len(f_verts):
                                    repeated_face = True
                                    break

                        if not repeated_face:
                            faces_verts_idx.append([v1, related_verts_in_common[0], v2])


        #### Keep only the faces that don't overlap by ignoring quads that overlap with two adjacent triangles.
        faces_to_not_include_idx = [] # Indices of faces_verts_idx to eliminate.
        all_faces_to_check_idx = faces_verts_idx + all_object_faces_verts_idx
        for i in range(len(faces_verts_idx)):
            for t in range(len(all_faces_to_check_idx)):
                if i != t:
                    verts_in_common = 0

                    if len(faces_verts_idx[i]) == 4 and len(all_faces_to_check_idx[t]) == 3:
                        for v_idx in all_faces_to_check_idx[t]:
                            if v_idx in faces_verts_idx[i]:
                                verts_in_common += 1

                        if verts_in_common == 3: # If it doesn't have all it's vertices repeated in the other face.
                            if not i in faces_to_not_include_idx:
                                faces_to_not_include_idx.append(i)


        #### Build faces discarding the ones in faces_to_not_include.
        me = object.data
        bm = bmesh.new()
        bm.from_mesh(me)

        num_faces_created = 0
        for i in range(len(faces_verts_idx)):
            if not i in faces_to_not_include_idx:
                bm.faces.new([ bm.verts[v] for v in faces_verts_idx[i] ])

                num_faces_created += 1

        bm.to_mesh(me)
        bm.free()



        for v_idx in selected_verts_idx:
            self.main_object.data.vertices[v_idx].select = True


        bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='EDIT')
        bpy.ops.mesh.normals_make_consistent(inside=False)
        bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='OBJECT')


        return num_faces_created



    #### Crosshatch skinning.
    def crosshatch_surface_invoke(self, ob_original_splines):
        self.is_crosshatch = False
        self.crosshatch_merge_distance = 0


        objects_to_delete = [] # duplicated strokes to be deleted.

        # If the main object uses modifiers deactivate them temporarily until the surface is joined. (without this the surface verts merging with the main object doesn't work well)
        self.modifiers_prev_viewport_state = []
        if len(self.main_object.modifiers) > 0:
            for m_idx in range(len(self.main_object.modifiers)):
                self.modifiers_prev_viewport_state.append(self.main_object.modifiers[m_idx].show_viewport)

                self.main_object.modifiers[m_idx].show_viewport = False


        bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
        bpy.data.objects[ob_original_splines.name].select = True
        bpy.context.scene.objects.active = bpy.data.objects[ob_original_splines.name]


        if len(ob_original_splines.data.splines) >= 2:
            bpy.ops.object.duplicate('INVOKE_REGION_WIN')
            ob_splines = bpy.context.object
            ob_splines.name = "SURFSKIO_NE_STR"


            #### Get estimative merge distance (sum up the distances from the first point to all other points, then average them and then divide them).
            first_point_dist_sum = 0
            first_dist = 0
            second_dist = 0
            coords_first_pt = ob_splines.data.splines[0].bezier_points[0].co
            for i in range(len(ob_splines.data.splines)):
                sp = ob_splines.data.splines[i]

                if coords_first_pt != sp.bezier_points[0].co:
                    first_dist = (coords_first_pt - sp.bezier_points[0].co).length

                if coords_first_pt != sp.bezier_points[len(sp.bezier_points) - 1].co:
                    second_dist = (coords_first_pt - sp.bezier_points[len(sp.bezier_points) - 1].co).length

                first_point_dist_sum += first_dist + second_dist


                if i == 0:
                    if first_dist != 0:
                        shortest_dist = first_dist
                    elif second_dist != 0:
                        shortest_dist = second_dist


                if shortest_dist > first_dist and first_dist != 0:
                    shortest_dist = first_dist

                if shortest_dist > second_dist and second_dist != 0:
                    shortest_dist = second_dist


            self.crosshatch_merge_distance = shortest_dist / 20



            #### Recalculation of merge distance.

            bpy.ops.object.duplicate('INVOKE_REGION_WIN')

            ob_calc_merge_dist = bpy.context.object
            ob_calc_merge_dist.name = "SURFSKIO_CALC_TMP"

            objects_to_delete.append(ob_calc_merge_dist)



            #### Smooth out strokes a little to improve crosshatch detection.
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
            bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='SELECT')

            for i in range(4):
                bpy.ops.curve.smooth('INVOKE_REGION_WIN')

            bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')



            #### Convert curves into mesh.
            ob_calc_merge_dist.data.resolution_u = 12
            bpy.ops.object.convert(target='MESH', keep_original=False)

            # Find "intersection-nodes".
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
            bpy.ops.mesh.select_all('INVOKE_REGION_WIN', action='SELECT')
            bpy.ops.mesh.remove_doubles('INVOKE_REGION_WIN', threshold=self.crosshatch_merge_distance)
            bpy.ops.mesh.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            # Remove verts with less than three edges.
            verts_edges_count = {}
            for ed in ob_calc_merge_dist.data.edges:
                v = ed.vertices

                if v[0] not in verts_edges_count:
                    verts_edges_count[v[0]] = 0

                if v[1] not in verts_edges_count:
                    verts_edges_count[v[1]] = 0

                verts_edges_count[v[0]] += 1
                verts_edges_count[v[1]] += 1

            nodes_verts_coords = []
            for v_idx in verts_edges_count:
                v = ob_calc_merge_dist.data.vertices[v_idx]

                if verts_edges_count[v_idx] < 3:
                    v.select = True


            # Remove them.
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
            bpy.ops.mesh.delete('INVOKE_REGION_WIN', type='VERT')
            bpy.ops.mesh.select_all('INVOKE_REGION_WIN', action='SELECT')

            # Remove doubles to discard very near verts from calculations of distance.
            bpy.ops.mesh.remove_doubles('INVOKE_REGION_WIN', threshold=self.crosshatch_merge_distance * 4.0)
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            # Get all coords of the resulting nodes.
            nodes_verts_coords = [(v.co[0], v.co[1], v.co[2]) for v in ob_calc_merge_dist.data.vertices]

            #### Check if the strokes are a crosshatch.
            if len(nodes_verts_coords) >= 3:
                self.is_crosshatch = True

                shortest_dist = None
                for co_1 in nodes_verts_coords:
                    for co_2 in nodes_verts_coords:
                        if co_1 != co_2:
                            dist = (mathutils.Vector(co_1) - mathutils.Vector(co_2)).length

                            if shortest_dist != None:
                                if dist < shortest_dist:
                                    shortest_dist = dist
                            else:
                                shortest_dist = dist

                self.crosshatch_merge_distance = shortest_dist / 3


            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.data.objects[ob_splines.name].select = True
            bpy.context.scene.objects.active = bpy.data.objects[ob_splines.name]

            #### Deselect all points.
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
            bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')



            #### Smooth splines in a localized way, to eliminate "saw-teeth" like shapes when there are many points.
            for sp in ob_splines.data.splines:
                angle_sum = 0

                angle_limit = 2 # Degrees
                for t in range(len(sp.bezier_points)):
                    if t <= len(sp.bezier_points) - 3: # Because on each iteration it checks the "next two points" of the actual. This way it doesn't go out of range.
                        p1 = sp.bezier_points[t]
                        p2 = sp.bezier_points[t + 1]
                        p3 = sp.bezier_points[t + 2]

                        vec_1 = p1.co - p2.co
                        vec_2 = p2.co - p3.co

                        if p2.co != p1.co and p2.co != p3.co:
                            angle = vec_1.angle(vec_2)
                            angle_sum += degrees(angle)

                            if angle_sum >= angle_limit: # If sum of angles is grater than the limit.
                                if (p1.co - p2.co).length <= self.crosshatch_merge_distance:
                                    p1.select_control_point = True; p1.select_left_handle = True; p1.select_right_handle = True
                                    p2.select_control_point = True; p2.select_left_handle = True; p2.select_right_handle = True

                                if (p1.co - p2.co).length <= self.crosshatch_merge_distance:
                                    p3.select_control_point = True; p3.select_left_handle = True; p3.select_right_handle = True

                                angle_sum = 0

                sp.bezier_points[0].select_control_point = False
                sp.bezier_points[0].select_left_handle = False
                sp.bezier_points[0].select_right_handle = False

                sp.bezier_points[len(sp.bezier_points) - 1].select_control_point = False
                sp.bezier_points[len(sp.bezier_points) - 1].select_left_handle = False
                sp.bezier_points[len(sp.bezier_points) - 1].select_right_handle  = False



            #### Smooth out strokes a little to improve crosshatch detection.
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            for i in range(15):
                bpy.ops.curve.smooth('INVOKE_REGION_WIN')

            bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')




            #### Simplify the splines.
            for sp in ob_splines.data.splines:
                angle_sum = 0

                sp.bezier_points[0].select_control_point = True
                sp.bezier_points[0].select_left_handle = True
                sp.bezier_points[0].select_right_handle = True

                sp.bezier_points[len(sp.bezier_points) - 1].select_control_point = True
                sp.bezier_points[len(sp.bezier_points) - 1].select_left_handle = True
                sp.bezier_points[len(sp.bezier_points) - 1].select_right_handle  = True


                angle_limit = 15 # Degrees
                for t in range(len(sp.bezier_points)):
                    if t <= len(sp.bezier_points) - 3: # Because on each iteration it checks the "next two points" of the actual. This way it doesn't go out of range.
                        p1 = sp.bezier_points[t]
                        p2 = sp.bezier_points[t + 1]
                        p3 = sp.bezier_points[t + 2]

                        vec_1 = p1.co - p2.co
                        vec_2 = p2.co - p3.co

                        if p2.co != p1.co and p2.co != p3.co:
                            angle = vec_1.angle(vec_2)
                            angle_sum += degrees(angle)

                            if angle_sum >= angle_limit: # If sum of angles is grater than the limit.
                                p1.select_control_point = True; p1.select_left_handle = True; p1.select_right_handle = True
                                p2.select_control_point = True; p2.select_left_handle = True; p2.select_right_handle = True
                                p3.select_control_point = True; p3.select_left_handle = True; p3.select_right_handle = True

                                angle_sum = 0



            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            bpy.ops.curve.select_all(action = 'INVERT')

            bpy.ops.curve.delete(type='VERT')
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')



            objects_to_delete.append(ob_splines)


            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
            bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')


            #### Check if the strokes are a crosshatch.
            if self.is_crosshatch:
                all_points_coords = []
                for i in range(len(ob_splines.data.splines)):
                    all_points_coords.append([])

                    all_points_coords[i] = [mathutils.Vector((x, y, z)) for x, y, z in [bp.co for bp in ob_splines.data.splines[i].bezier_points]]


                all_intersections = []
                checked_splines = []
                for i in range(len(all_points_coords)):

                    for t in range(len(all_points_coords[i]) - 1):
                        bp1_co = all_points_coords[i][t]
                        bp2_co = all_points_coords[i][t + 1]

                        for i2 in range(len(all_points_coords)):
                            if i != i2 and not i2 in checked_splines:
                                for t2 in range(len(all_points_coords[i2]) - 1):
                                    bp3_co = all_points_coords[i2][t2]
                                    bp4_co = all_points_coords[i2][t2 + 1]


                                    intersec_coords = mathutils.geometry.intersect_line_line(bp1_co, bp2_co, bp3_co, bp4_co)

                                    if intersec_coords != None:
                                        dist = (intersec_coords[0] - intersec_coords[1]).length

                                        if dist <= self.crosshatch_merge_distance * 1.5:
                                            temp_co, percent1 = mathutils.geometry.intersect_point_line(intersec_coords[0], bp1_co, bp2_co)

                                            if (percent1 >= -0.02 and percent1 <= 1.02):
                                                temp_co, percent2 = mathutils.geometry.intersect_point_line(intersec_coords[1], bp3_co, bp4_co)
                                                if (percent2 >= -0.02 and percent2 <= 1.02):
                                                    all_intersections.append((i, t, percent1, ob_splines.matrix_world * intersec_coords[0])) # Format: spline index, first point index from corresponding segment, percentage from first point of actual segment, coords of intersection point.
                                                    all_intersections.append((i2, t2, percent2, ob_splines.matrix_world * intersec_coords[1]))



                        checked_splines.append(i)


                all_intersections.sort(key = operator.itemgetter(0,1,2)) # Sort list by spline, then by corresponding first point index of segment, and then by percentage from first point of segment: elements 0 and 1 respectively.



                self.crosshatch_strokes_coords = {}
                for i in range(len(all_intersections)):
                    if not all_intersections[i][0] in self.crosshatch_strokes_coords:
                        self.crosshatch_strokes_coords[all_intersections[i][0]] = []

                    self.crosshatch_strokes_coords[all_intersections[i][0]].append(all_intersections[i][3]) # Save intersection coords.

            else:
                self.is_crosshatch = False


        #### Delete all duplicates.
        for o in objects_to_delete:
            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.data.objects[o.name].select = True
            bpy.context.scene.objects.active = bpy.data.objects[o.name]
            bpy.ops.object.delete()


        #### If the main object has modifiers, turn their "viewport view status" to what it was before the forced deactivation above.
        if len(self.main_object.modifiers) > 0:
            for m_idx in range(len(self.main_object.modifiers)):
                self.main_object.modifiers[m_idx].show_viewport = self.modifiers_prev_viewport_state[m_idx]



        return



    #### Part of the Crosshatch process that is repeated when the operator is tweaked.
    def crosshatch_surface_execute(self):
        # If the main object uses modifiers deactivate them temporarily until the surface is joined. (without this the surface verts merging with the main object doesn't work well)
        self.modifiers_prev_viewport_state = []
        if len(self.main_object.modifiers) > 0:
            for m_idx in range(len(self.main_object.modifiers)):
                self.modifiers_prev_viewport_state.append(self.main_object.modifiers[m_idx].show_viewport)

                self.main_object.modifiers[m_idx].show_viewport = False


        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')



        me_name = "SURFSKIO_STK_TMP"
        me = bpy.data.meshes.new(me_name)

        all_verts_coords = []
        all_edges = []
        for st_idx in self.crosshatch_strokes_coords:
            for co_idx in range(len(self.crosshatch_strokes_coords[st_idx])):
                coords = self.crosshatch_strokes_coords[st_idx][co_idx]

                all_verts_coords.append(coords)

                if co_idx > 0:
                    all_edges.append((len(all_verts_coords) - 2, len(all_verts_coords) - 1))


        me.from_pydata(all_verts_coords, all_edges, [])

        me.update()

        ob = bpy.data.objects.new(me_name, me)
        ob.data = me
        bpy.context.scene.objects.link(ob)


        bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
        bpy.data.objects[ob.name].select = True
        bpy.context.scene.objects.active = bpy.data.objects[ob.name]


        #### Get together each vert and its nearest, to the middle position.
        verts = ob.data.vertices
        checked_verts = []
        for i in range(len(verts)):
            shortest_dist = None

            if not i in checked_verts:
                for t in range(len(verts)):
                    if i != t and not t in checked_verts:
                        dist = (verts[i].co - verts[t].co).length

                        if shortest_dist != None:
                            if dist < shortest_dist:
                                shortest_dist = dist
                                nearest_vert = t
                        else:
                            shortest_dist = dist
                            nearest_vert = t

                middle_location = (verts[i].co + verts[nearest_vert].co) / 2

                verts[i].co = middle_location
                verts[nearest_vert].co = middle_location

                checked_verts.append(i)
                checked_verts.append(nearest_vert)




        #### Calculate average length between all the generated edges.
        ob = bpy.context.object
        lengths_sum = 0
        for ed in ob.data.edges:
            v1 = ob.data.vertices[ed.vertices[0]]
            v2 = ob.data.vertices[ed.vertices[1]]

            lengths_sum += (v1.co - v2.co).length

        edges_count = len(ob.data.edges)

        average_edge_length = lengths_sum / edges_count


        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
        bpy.ops.mesh.select_all('INVOKE_REGION_WIN', action='SELECT')
        bpy.ops.mesh.remove_doubles('INVOKE_REGION_WIN', threshold=average_edge_length / 15.0)
        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

        final_points_ob = bpy.context.scene.objects.active


        #### Make a dictionary with the verts related to each vert.
        related_key_verts = {}
        for ed in final_points_ob.data.edges:
            if not ed.vertices[0] in related_key_verts:
                related_key_verts[ed.vertices[0]] = []

            if not ed.vertices[1] in related_key_verts:
                related_key_verts[ed.vertices[1]] = []


            if not ed.vertices[1] in related_key_verts[ed.vertices[0]]:
                related_key_verts[ed.vertices[0]].append(ed.vertices[1])

            if not ed.vertices[0] in related_key_verts[ed.vertices[1]]:
                related_key_verts[ed.vertices[1]].append(ed.vertices[0])



        #### Get groups of verts forming each face.
        faces_verts_idx = []
        for v1 in related_key_verts: # verts-1 ....
            for v2 in related_key_verts: # verts-2
                if v1 != v2:
                    related_verts_in_common = []
                    v2_in_rel_v1 = False
                    v1_in_rel_v2 = False
                    for rel_v1 in related_key_verts[v1]:
                        if rel_v1 in related_key_verts[v2]: # Check if related verts of verts-1 are related verts of verts-2.
                            related_verts_in_common.append(rel_v1)

                    if v2 in related_key_verts[v1]:
                        v2_in_rel_v1 = True

                    if v1 in related_key_verts[v2]:
                        v1_in_rel_v2 = True


                    repeated_face = False
                    # If two verts have two related verts in common, they form a quad.
                    if len(related_verts_in_common) == 2:
                        # Check if the face is already saved.
                        for f_verts in faces_verts_idx:
                            repeated_verts = 0

                            if len(f_verts) == 4:
                                if v1 in f_verts: repeated_verts += 1
                                if v2 in f_verts: repeated_verts += 1
                                if related_verts_in_common[0] in f_verts: repeated_verts += 1
                                if related_verts_in_common[1] in f_verts: repeated_verts += 1

                                if repeated_verts == len(f_verts):
                                    repeated_face = True
                                    break

                        if not repeated_face:
                            faces_verts_idx.append([v1, related_verts_in_common[0], v2, related_verts_in_common[1]])

                    elif v2_in_rel_v1 and v1_in_rel_v2 and len(related_verts_in_common) == 1: # If Two verts have one related vert in common and they are related to each other, they form a triangle.
                        # Check if the face is already saved.
                        for f_verts in faces_verts_idx:
                            repeated_verts = 0

                            if len(f_verts) == 3:
                                if v1 in f_verts: repeated_verts += 1
                                if v2 in f_verts: repeated_verts += 1
                                if related_verts_in_common[0] in f_verts: repeated_verts += 1

                                if repeated_verts == len(f_verts):
                                    repeated_face = True
                                    break

                        if not repeated_face:
                            faces_verts_idx.append([v1, related_verts_in_common[0], v2])


        #### Keep only the faces that don't overlap by ignoring quads that overlap with two adjacent triangles.
        faces_to_not_include_idx = [] # Indices of faces_verts_idx to eliminate.
        for i in range(len(faces_verts_idx)):
            for t in range(len(faces_verts_idx)):
                if i != t:
                    verts_in_common = 0

                    if len(faces_verts_idx[i]) == 4 and len(faces_verts_idx[t]) == 3:
                        for v_idx in faces_verts_idx[t]:
                            if v_idx in faces_verts_idx[i]:
                                verts_in_common += 1

                        if verts_in_common == 3: # If it doesn't have all it's vertices repeated in the other face.
                            if not i in faces_to_not_include_idx:
                                faces_to_not_include_idx.append(i)


        #### Build surface.
        all_surface_verts_co = []
        verts_idx_translation = {}
        for i in range(len(final_points_ob.data.vertices)):
            coords = final_points_ob.data.vertices[i].co
            all_surface_verts_co.append([coords[0], coords[1], coords[2]])

        # Verts of each face.
        all_surface_faces = []
        for i in range(len(faces_verts_idx)):
            if not i in faces_to_not_include_idx:
                face = []
                for v_idx in faces_verts_idx[i]:
                    face.append(v_idx)

                all_surface_faces.append(face)

        # Build the mesh.
        surf_me_name = "SURFSKIO_surface"
        me_surf = bpy.data.meshes.new(surf_me_name)

        me_surf.from_pydata(all_surface_verts_co, [], all_surface_faces)

        me_surf.update()

        ob_surface = bpy.data.objects.new(surf_me_name, me_surf)
        bpy.context.scene.objects.link(ob_surface)

        # Delete final points temporal object
        bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
        bpy.data.objects[final_points_ob.name].select = True
        bpy.context.scene.objects.active = bpy.data.objects[final_points_ob.name]

        bpy.ops.object.delete()


        # Delete isolated verts if there are any.
        bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
        bpy.data.objects[ob_surface.name].select = True
        bpy.context.scene.objects.active = bpy.data.objects[ob_surface.name]

        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
        bpy.ops.mesh.select_all(action='DESELECT')
        bpy.ops.mesh.select_face_by_sides(type='NOTEQUAL')
        bpy.ops.mesh.delete()
        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')



        #### Join crosshatch results with original mesh.

        # Calculate a distance to merge the verts of the crosshatch surface to the main object.
        edges_length_sum = 0
        for ed in ob_surface.data.edges:
            edges_length_sum += (ob_surface.data.vertices[ed.vertices[0]].co - ob_surface.data.vertices[ed.vertices[1]].co).length

        if len(ob_surface.data.edges) > 0:
            average_surface_edges_length = edges_length_sum / len(ob_surface.data.edges)
        else:
            average_surface_edges_length = 0.0001

        # Make dictionary with all the verts connected to each vert, on the new surface object.
        surface_connected_verts = {}
        for ed in ob_surface.data.edges:
            if not ed.vertices[0] in surface_connected_verts:
                surface_connected_verts[ed.vertices[0]] = []

            surface_connected_verts[ed.vertices[0]].append(ed.vertices[1])


            if not ed.vertices[1] in surface_connected_verts:
                surface_connected_verts[ed.vertices[1]] = []

            surface_connected_verts[ed.vertices[1]].append(ed.vertices[0])



        # Duplicate the new surface object, and use shrinkwrap to calculate later the nearest verts to the main object.
        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
        bpy.ops.mesh.select_all('INVOKE_REGION_WIN', action='DESELECT')
        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

        bpy.ops.object.duplicate('INVOKE_REGION_WIN')

        final_ob_duplicate = bpy.context.scene.objects.active

        bpy.ops.object.modifier_add('INVOKE_REGION_WIN', type='SHRINKWRAP')
        final_ob_duplicate.modifiers["Shrinkwrap"].wrap_method = "NEAREST_VERTEX"
        final_ob_duplicate.modifiers["Shrinkwrap"].target = self.main_object

        bpy.ops.object.modifier_apply('INVOKE_REGION_WIN', apply_as='DATA', modifier='Shrinkwrap')


        # Make list with verts of original mesh as index and coords as value.
        main_object_verts_coords = []
        for v in self.main_object.data.vertices:
            coords = self.main_object.matrix_world * v.co

            for c in range(len(coords)): # To avoid problems when taking "-0.00" as a different value as "0.00".
                if "%.3f" % coords[c] == "-0.00":
                    coords[c] = 0

            main_object_verts_coords.append(["%.3f" % coords[0], "%.3f" % coords[1], "%.3f" % coords[2]])

        tuple(main_object_verts_coords)


        # Determine which verts will be merged, snap them to the nearest verts on the original verts, and get them selected.
        crosshatch_verts_to_merge = []
        if self.automatic_join:
            for i in range(len(ob_surface.data.vertices)):
                # Calculate the distance from each of the connected verts to the actual vert, and compare it with the distance they would have if joined. If they don't change much, that vert can be joined.
                merge_actual_vert = True
                if len(surface_connected_verts[i]) < 4:
                    for c_v_idx in surface_connected_verts[i]:
                        points_original = []
                        points_original.append(ob_surface.data.vertices[c_v_idx].co)
                        points_original.append(ob_surface.data.vertices[i].co)

                        points_target = []
                        points_target.append(ob_surface.data.vertices[c_v_idx].co)
                        points_target.append(final_ob_duplicate.data.vertices[i].co)

                        vec_A = points_original[0] - points_original[1]
                        vec_B = points_target[0] - points_target[1]

                        dist_A = (points_original[0] - points_original[1]).length
                        dist_B = (points_target[0] - points_target[1]).length


                        if not (points_original[0] == points_original[1] or points_target[0] == points_target[1]): # If any vector's length is zero.
                            angle = vec_A.angle(vec_B) / math.pi
                        else:
                            angle= 0


                        if dist_B > dist_A * 1.7 * self.join_stretch_factor or dist_B < dist_A / 2 / self.join_stretch_factor or angle >= 0.15 * self.join_stretch_factor: # Set a range of acceptable variation in the connected edges.
                            merge_actual_vert = False
                            break
                else:
                    merge_actual_vert = False


                if merge_actual_vert:
                    coords = final_ob_duplicate.data.vertices[i].co

                    for c in range(len(coords)): # To avoid problems when taking "-0.000" as a different value as "0.00".
                        if "%.3f" % coords[c] == "-0.00":
                            coords[c] = 0

                    comparison_coords = ["%.3f" % coords[0], "%.3f" % coords[1], "%.3f" % coords[2]]


                    if comparison_coords in main_object_verts_coords:
                        main_object_related_vert_idx = main_object_verts_coords.index(comparison_coords) # Get the index of the vert with those coords in the main object.

                        if self.main_object.data.vertices[main_object_related_vert_idx].select == True or self.main_object_selected_verts_count == 0:
                            ob_surface.data.vertices[i].co = final_ob_duplicate.data.vertices[i].co
                            ob_surface.data.vertices[i].select = True
                            crosshatch_verts_to_merge.append(i)

                            # Make sure the vert in the main object is selected, in case it wasn't selected and the "join crosshatch" option is active.
                            self.main_object.data.vertices[main_object_related_vert_idx].select = True




        # Delete duplicated object.
        bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
        bpy.data.objects[final_ob_duplicate.name].select = True
        bpy.context.scene.objects.active = bpy.data.objects[final_ob_duplicate.name]
        bpy.ops.object.delete()


        # Join crosshatched surface and main object.
        bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
        bpy.data.objects[ob_surface.name].select = True
        bpy.data.objects[self.main_object.name].select = True
        bpy.context.scene.objects.active = bpy.data.objects[self.main_object.name]

        bpy.ops.object.join('INVOKE_REGION_WIN')

        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
        # Perform Remove doubles to merge verts.
        if not (self.automatic_join == False and self.main_object_selected_verts_count == 0):
            bpy.ops.mesh.remove_doubles(threshold=0.0001)

        bpy.ops.mesh.select_all(action='DESELECT')


        #### If the main object has modifiers, turn their "viewport view status" to what it was before the forced deactivation above.
        if len(self.main_object.modifiers) > 0:
            for m_idx in range(len(self.main_object.modifiers)):
                self.main_object.modifiers[m_idx].show_viewport = self.modifiers_prev_viewport_state[m_idx]



        return{'FINISHED'}



    def rectangular_surface(self):
        #### Selected edges.
        all_selected_edges_idx = []
        all_selected_verts = []
        all_verts_idx = []
        for ed in self.main_object.data.edges:
            if ed.select:
                all_selected_edges_idx.append(ed.index)

                # Selected vertices.
                if not ed.vertices[0] in all_selected_verts:
                    all_selected_verts.append(self.main_object.data.vertices[ed.vertices[0]])
                if not ed.vertices[1] in all_selected_verts:
                    all_selected_verts.append(self.main_object.data.vertices[ed.vertices[1]])

                # All verts (both from each edge) to determine later which are at the tips (those not repeated twice).
                all_verts_idx.append(ed.vertices[0])
                all_verts_idx.append(ed.vertices[1])



        #### Identify the tips and "middle-vertex" that separates U from V, if there is one.
        all_chains_tips_idx = []
        for v_idx in all_verts_idx:
            if all_verts_idx.count(v_idx) < 2:
                all_chains_tips_idx.append(v_idx)



        edges_connected_to_tips = []
        for ed in self.main_object.data.edges:
            if (ed.vertices[0] in all_chains_tips_idx or ed.vertices[1] in all_chains_tips_idx) and not (ed.vertices[0] in all_verts_idx and ed.vertices[1] in all_verts_idx):
                edges_connected_to_tips.append(ed)


        #### Check closed selections.
        single_unselected_verts_and_neighbors = [] # List with groups of three verts, where the first element of the pair is the unselected vert of a closed selection and the other two elements are the selected neighbor verts (it will be useful to determine which selection chain the unselected vert belongs to, and determine the "middle-vertex")

        # To identify a "closed" selection (a selection that is a closed chain except for one vertex) find the vertex in common that have the edges connected to tips. If there is a vertex in common, that one is the unselected vert that closes the selection or is a "middle-vertex".
        single_unselected_verts = []
        for ed in edges_connected_to_tips:
            for ed_b in edges_connected_to_tips:
                if ed != ed_b:
                    if ed.vertices[0] == ed_b.vertices[0] and not self.main_object.data.vertices[ed.vertices[0]].select and ed.vertices[0] not in single_unselected_verts:
                        single_unselected_verts_and_neighbors.append([ed.vertices[0], ed.vertices[1], ed_b.vertices[1]]) # The second element is one of the tips of the selected vertices of the closed selection.
                        single_unselected_verts.append(ed.vertices[0])
                        break
                    elif ed.vertices[0] == ed_b.vertices[1] and not self.main_object.data.vertices[ed.vertices[0]].select and ed.vertices[0] not in single_unselected_verts:
                        single_unselected_verts_and_neighbors.append([ed.vertices[0], ed.vertices[1], ed_b.vertices[0]])
                        single_unselected_verts.append(ed.vertices[0])
                        break
                    elif ed.vertices[1] == ed_b.vertices[0] and not self.main_object.data.vertices[ed.vertices[1]].select and ed.vertices[1] not in single_unselected_verts:
                        single_unselected_verts_and_neighbors.append([ed.vertices[1], ed.vertices[0], ed_b.vertices[1]])
                        single_unselected_verts.append(ed.vertices[1])
                        break
                    elif ed.vertices[1] == ed_b.vertices[1] and not self.main_object.data.vertices[ed.vertices[1]].select and ed.vertices[1] not in single_unselected_verts:
                        single_unselected_verts_and_neighbors.append([ed.vertices[1], ed.vertices[0], ed_b.vertices[0]])
                        single_unselected_verts.append(ed.vertices[1])
                        break


        middle_vertex_idx = None
        tips_to_discard_idx = []
        # Check if there is a "middle-vertex", and get its index.
        for i in range(0, len(single_unselected_verts_and_neighbors)):
            actual_chain_verts = self.get_ordered_verts(self.main_object, all_selected_edges_idx, all_verts_idx, single_unselected_verts_and_neighbors[i][1], None, None)

            if single_unselected_verts_and_neighbors[i][2] != actual_chain_verts[len(actual_chain_verts) - 1].index:
                middle_vertex_idx = single_unselected_verts_and_neighbors[i][0]
                tips_to_discard_idx.append(single_unselected_verts_and_neighbors[i][1])
                tips_to_discard_idx.append(single_unselected_verts_and_neighbors[i][2])


        #### List with pairs of verts that belong to the tips of each selection chain (row).
        verts_tips_same_chain_idx = []
        if len(all_chains_tips_idx) >= 2:
            checked_v = []
            for i in range(0, len(all_chains_tips_idx)):
                if all_chains_tips_idx[i] not in checked_v:
                    v_chain = self.get_ordered_verts(self.main_object, all_selected_edges_idx, all_verts_idx, all_chains_tips_idx[i], middle_vertex_idx, None)

                    verts_tips_same_chain_idx.append([v_chain[0].index, v_chain[len(v_chain) - 1].index])

                    checked_v.append(v_chain[0].index)
                    checked_v.append(v_chain[len(v_chain) - 1].index)


        #### Selection tips (vertices).
        verts_tips_parsed_idx = []
        if len(all_chains_tips_idx) >= 2:
            for spec_v_idx in all_chains_tips_idx:
                if (spec_v_idx not in tips_to_discard_idx):
                    verts_tips_parsed_idx.append(spec_v_idx)


        #### Identify the type of selection made by the user.
        if middle_vertex_idx != None:
            if len(all_chains_tips_idx) == 4 and len(single_unselected_verts_and_neighbors) == 1: # If there are 4 tips (two selection chains), and there is only one single unselected vert (the middle vert).
                selection_type = "TWO_CONNECTED"
            else:
                # The type of the selection was not identified, the script stops.
                self.report({'WARNING'}, "The selection isn't valid.")
                bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
                self.cleanup_on_interruption()
                self.stopping_errors = True

                return{'CANCELLED'}
        else:
            if len(all_chains_tips_idx) == 2: # If there are 2 tips
                selection_type = "SINGLE"
            elif len(all_chains_tips_idx) == 4: # If there are 4 tips
                selection_type = "TWO_NOT_CONNECTED"
            elif len(all_chains_tips_idx) == 0:
                if len(self.main_splines.data.splines) > 1:
                    selection_type = "NO_SELECTION"
                else:
                    # If the selection was not identified and there is only one stroke, there's no possibility to build a surface, so the script is interrupted.
                    self.report({'WARNING'}, "The selection isn't valid.")
                    bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
                    self.cleanup_on_interruption()
                    self.stopping_errors = True

                    return{'CANCELLED'}
            else:
                # The type of the selection was not identified, the script stops.
                self.report({'WARNING'}, "The selection isn't valid.")

                bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
                self.cleanup_on_interruption()

                self.stopping_errors = True

                return{'CANCELLED'}



        #### If the selection type is TWO_NOT_CONNECTED and there is only one stroke, stop the script.
        if selection_type == "TWO_NOT_CONNECTED" and len(self.main_splines.data.splines) == 1:
            self.report({'WARNING'}, "At least two strokes are needed when there are two not connected selections.")
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
            self.cleanup_on_interruption()
            self.stopping_errors = True

            return{'CANCELLED'}



        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

        bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
        bpy.data.objects[self.main_splines.name].select = True
        bpy.context.scene.objects.active = bpy.context.scene.objects[self.main_splines.name]


        #### Enter editmode for the new curve (converted from grease pencil strokes), to smooth it out.
        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
        bpy.ops.curve.smooth('INVOKE_REGION_WIN')
        bpy.ops.curve.smooth('INVOKE_REGION_WIN')
        bpy.ops.curve.smooth('INVOKE_REGION_WIN')
        bpy.ops.curve.smooth('INVOKE_REGION_WIN')
        bpy.ops.curve.smooth('INVOKE_REGION_WIN')
        bpy.ops.curve.smooth('INVOKE_REGION_WIN')
        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')


        self.selection_U_exists = False
        self.selection_U2_exists = False
        self.selection_V_exists = False
        self.selection_V2_exists = False

        self.selection_U_is_closed = False
        self.selection_U2_is_closed = False
        self.selection_V_is_closed = False
        self.selection_V2_is_closed = False

        #### Define what vertices are at the tips of each selection and are not the middle-vertex.
        if selection_type == "TWO_CONNECTED":
            self.selection_U_exists = True
            self.selection_V_exists = True

            closing_vert_U_idx = None
            closing_vert_V_idx = None
            closing_vert_U2_idx = None
            closing_vert_V2_idx = None

            # Determine which selection is Selection-U and which is Selection-V.
            points_A = []
            points_B = []
            points_first_stroke_tips = []

            points_A.append(self.main_object.matrix_world * self.main_object.data.vertices[verts_tips_parsed_idx[0]].co)
            points_A.append(self.main_object.matrix_world * self.main_object.data.vertices[middle_vertex_idx].co)

            points_B.append(self.main_object.matrix_world * self.main_object.data.vertices[verts_tips_parsed_idx[1]].co)
            points_B.append(self.main_object.matrix_world * self.main_object.data.vertices[middle_vertex_idx].co)

            points_first_stroke_tips.append(self.main_splines.data.splines[0].bezier_points[0].co)
            points_first_stroke_tips.append(self.main_splines.data.splines[0].bezier_points[len(self.main_splines.data.splines[0].bezier_points) - 1].co)

            angle_A = self.orientation_difference(points_A, points_first_stroke_tips)
            angle_B = self.orientation_difference(points_B, points_first_stroke_tips)

            if angle_A < angle_B:
                first_vert_U_idx = verts_tips_parsed_idx[0]
                first_vert_V_idx = verts_tips_parsed_idx[1]
            else:
                first_vert_U_idx = verts_tips_parsed_idx[1]
                first_vert_V_idx = verts_tips_parsed_idx[0]

        elif selection_type == "SINGLE" or selection_type == "TWO_NOT_CONNECTED":
            first_sketched_point_first_stroke_co = self.main_splines.data.splines[0].bezier_points[0].co
            last_sketched_point_first_stroke_co = self.main_splines.data.splines[0].bezier_points[len(self.main_splines.data.splines[0].bezier_points) - 1].co
            first_sketched_point_last_stroke_co = self.main_splines.data.splines[len(self.main_splines.data.splines) - 1].bezier_points[0].co
            if len(self.main_splines.data.splines) > 1:
                first_sketched_point_second_stroke_co = self.main_splines.data.splines[1].bezier_points[0].co
                last_sketched_point_second_stroke_co = self.main_splines.data.splines[1].bezier_points[len(self.main_splines.data.splines[1].bezier_points) - 1].co


            single_unselected_neighbors = [] # Only the neighbors of the single unselected verts.
            for verts_neig_idx in single_unselected_verts_and_neighbors:
                single_unselected_neighbors.append(verts_neig_idx[1])
                single_unselected_neighbors.append(verts_neig_idx[2])


            all_chains_tips_and_middle_vert = []
            for v_idx in all_chains_tips_idx:
                if v_idx not in single_unselected_neighbors:
                    all_chains_tips_and_middle_vert.append(v_idx)


            all_chains_tips_and_middle_vert += single_unselected_verts

            all_participating_verts = all_chains_tips_and_middle_vert + all_verts_idx

            # The tip of the selected vertices nearest to the first point of the first sketched stroke.
            nearest_tip_to_first_st_first_pt_idx, shortest_distance_to_first_stroke = self.shortest_distance(self.main_object, first_sketched_point_first_stroke_co, all_chains_tips_and_middle_vert)
            # If the nearest tip is not from a closed selection, get the opposite tip vertex index.
            if nearest_tip_to_first_st_first_pt_idx not in single_unselected_verts or nearest_tip_to_first_st_first_pt_idx == middle_vertex_idx:
                nearest_tip_to_first_st_first_pt_opposite_idx = self.opposite_tip(nearest_tip_to_first_st_first_pt_idx, verts_tips_same_chain_idx)

            # The tip of the selected vertices nearest to the last point of the first sketched stroke.
            nearest_tip_to_first_st_last_pt_idx, temp_dist = self.shortest_distance(self.main_object, last_sketched_point_first_stroke_co, all_chains_tips_and_middle_vert)

            # The tip of the selected vertices nearest to the first point of the last sketched stroke.
            nearest_tip_to_last_st_first_pt_idx, shortest_distance_to_last_stroke = self.shortest_distance(self.main_object, first_sketched_point_last_stroke_co, all_chains_tips_and_middle_vert)

            if len(self.main_splines.data.splines) > 1:
                # The selected vertex nearest to the first point of the second sketched stroke. (This will be useful to determine the direction of the closed selection V when extruding along strokes)
                nearest_vert_to_second_st_first_pt_idx, temp_dist = self.shortest_distance(self.main_object, first_sketched_point_second_stroke_co, all_verts_idx)

                # The selected vertex nearest to the first point of the second sketched stroke. (This will be useful to determine the direction of the closed selection V2 when extruding along strokes)
                nearest_vert_to_second_st_last_pt_idx, temp_dist = self.shortest_distance(self.main_object, last_sketched_point_second_stroke_co, all_verts_idx)



            # Determine if the single selection will be treated as U or as V.
            edges_sum = 0
            for i in all_selected_edges_idx:
                edges_sum += ((self.main_object.matrix_world * self.main_object.data.vertices[self.main_object.data.edges[i].vertices[0]].co) - (self.main_object.matrix_world * self.main_object.data.vertices[self.main_object.data.edges[i].vertices[1]].co)).length

            average_edge_length = edges_sum / len(all_selected_edges_idx)


            # Get shortest distance from the first point of the last stroke to any participating vertex.
            temp_idx, shortest_distance_to_last_stroke = self.shortest_distance(self.main_object, first_sketched_point_last_stroke_co, all_participating_verts)


            if shortest_distance_to_first_stroke < average_edge_length / 4 and shortest_distance_to_last_stroke < average_edge_length and len(self.main_splines.data.splines) > 1: # If the beginning of the first stroke is near enough, and its orientation difference with the first edge of the nearest selection chain is not too high, interpret things as an "extrude along strokes" instead of "extrude through strokes"
                self.selection_U_exists = False
                self.selection_V_exists = True
                if nearest_tip_to_first_st_first_pt_idx not in single_unselected_verts or nearest_tip_to_first_st_first_pt_idx == middle_vertex_idx: # If the first selection is not closed.
                    self.selection_V_is_closed = False
                    first_neighbor_V_idx = None
                    closing_vert_U_idx = None
                    closing_vert_U2_idx = None
                    closing_vert_V_idx = None
                    closing_vert_V2_idx = None

                    first_vert_V_idx = nearest_tip_to_first_st_first_pt_idx

                    if selection_type == "TWO_NOT_CONNECTED":
                        self.selection_V2_exists = True

                        first_vert_V2_idx = nearest_tip_to_first_st_last_pt_idx
                else:
                    self.selection_V_is_closed = True
                    closing_vert_V_idx = nearest_tip_to_first_st_first_pt_idx

                    # Get the neighbors of the first (unselected) vert of the closed selection U.
                    vert_neighbors = []
                    for verts in single_unselected_verts_and_neighbors:
                        if verts[0] == nearest_tip_to_first_st_first_pt_idx:
                            vert_neighbors.append(verts[1])
                            vert_neighbors.append(verts[2])
                            break

                    verts_V = self.get_ordered_verts(self.main_object, all_selected_edges_idx, all_verts_idx, vert_neighbors[0], middle_vertex_idx, None)

                    for i in range(0, len(verts_V)):
                        if verts_V[i].index == nearest_vert_to_second_st_first_pt_idx:
                            if i >= len(verts_V) / 2: # If the vertex nearest to the first point of the second stroke is in the first half of the selected verts.
                                first_vert_V_idx = vert_neighbors[1]
                                break
                            else:
                                first_vert_V_idx = vert_neighbors[0]
                                break



                if selection_type == "TWO_NOT_CONNECTED":
                    self.selection_V2_exists = True

                    if nearest_tip_to_first_st_last_pt_idx not in single_unselected_verts or nearest_tip_to_first_st_last_pt_idx == middle_vertex_idx: # If the second selection is not closed.
                        self.selection_V2_is_closed = False
                        first_neighbor_V2_idx = None
                        closing_vert_V2_idx = None

                        first_vert_V2_idx = nearest_tip_to_first_st_last_pt_idx

                    else:
                        self.selection_V2_is_closed = True
                        closing_vert_V2_idx = nearest_tip_to_first_st_last_pt_idx

                        # Get the neighbors of the first (unselected) vert of the closed selection U.
                        vert_neighbors = []
                        for verts in single_unselected_verts_and_neighbors:
                            if verts[0] == nearest_tip_to_first_st_last_pt_idx:
                                vert_neighbors.append(verts[1])
                                vert_neighbors.append(verts[2])
                                break


                        verts_V2 = self.get_ordered_verts(self.main_object, all_selected_edges_idx, all_verts_idx, vert_neighbors[0], middle_vertex_idx, None)

                        for i in range(0, len(verts_V2)):
                            if verts_V2[i].index == nearest_vert_to_second_st_last_pt_idx:
                                if i >= len(verts_V2) / 2: # If the vertex nearest to the first point of the second stroke is in the first half of the selected verts.
                                    first_vert_V2_idx = vert_neighbors[1]
                                    break
                                else:
                                    first_vert_V2_idx = vert_neighbors[0]
                                    break

                else:
                    self.selection_V2_exists = False

            else:
                self.selection_U_exists = True
                self.selection_V_exists = False
                if nearest_tip_to_first_st_first_pt_idx not in single_unselected_verts or nearest_tip_to_first_st_first_pt_idx == middle_vertex_idx: # If the first selection is not closed.
                    self.selection_U_is_closed = False
                    first_neighbor_U_idx = None
                    closing_vert_U_idx = None

                    points_tips = []
                    points_tips.append(self.main_object.matrix_world * self.main_object.data.vertices[nearest_tip_to_first_st_first_pt_idx].co)
                    points_tips.append(self.main_object.matrix_world * self.main_object.data.vertices[nearest_tip_to_first_st_first_pt_opposite_idx].co)

                    points_first_stroke_tips = []
                    points_first_stroke_tips.append(self.main_splines.data.splines[0].bezier_points[0].co)
                    points_first_stroke_tips.append(self.main_splines.data.splines[0].bezier_points[len(self.main_splines.data.splines[0].bezier_points) - 1].co)

                    vec_A = points_tips[0] - points_tips[1]
                    vec_B = points_first_stroke_tips[0] - points_first_stroke_tips[1]

                    # Compare the direction of the selection and the first grease pencil stroke to determine which is the "first" vertex of the selection.
                    if vec_A.dot(vec_B) < 0:
                        first_vert_U_idx = nearest_tip_to_first_st_first_pt_opposite_idx
                    else:
                        first_vert_U_idx = nearest_tip_to_first_st_first_pt_idx

                else:
                    self.selection_U_is_closed = True
                    closing_vert_U_idx = nearest_tip_to_first_st_first_pt_idx

                    # Get the neighbors of the first (unselected) vert of the closed selection U.
                    vert_neighbors = []
                    for verts in single_unselected_verts_and_neighbors:
                        if verts[0] == nearest_tip_to_first_st_first_pt_idx:
                            vert_neighbors.append(verts[1])
                            vert_neighbors.append(verts[2])
                            break

                    points_first_and_neighbor = []
                    points_first_and_neighbor.append(self.main_object.matrix_world * self.main_object.data.vertices[nearest_tip_to_first_st_first_pt_idx].co)
                    points_first_and_neighbor.append(self.main_object.matrix_world * self.main_object.data.vertices[vert_neighbors[0]].co)

                    points_first_stroke_tips = []
                    points_first_stroke_tips.append(self.main_splines.data.splines[0].bezier_points[0].co)
                    points_first_stroke_tips.append(self.main_splines.data.splines[0].bezier_points[1].co)

                    vec_A = points_first_and_neighbor[0] - points_first_and_neighbor[1]
                    vec_B = points_first_stroke_tips[0] - points_first_stroke_tips[1]

                    # Compare the direction of the selection and the first grease pencil stroke to determine which is the vertex neighbor to the first vertex (unselected) of the closed selection. This will determine the direction of the closed selection.
                    if vec_A.dot(vec_B) < 0:
                        first_vert_U_idx = vert_neighbors[1]
                    else:
                        first_vert_U_idx = vert_neighbors[0]



                if selection_type == "TWO_NOT_CONNECTED":
                    self.selection_U2_exists = True

                    if nearest_tip_to_last_st_first_pt_idx not in single_unselected_verts or nearest_tip_to_last_st_first_pt_idx == middle_vertex_idx: # If the second selection is not closed.
                        self.selection_U2_is_closed = False
                        first_neighbor_U2_idx = None
                        closing_vert_U2_idx = None

                        first_vert_U2_idx = nearest_tip_to_last_st_first_pt_idx

                    else:
                        self.selection_U2_is_closed = True
                        closing_vert_U2_idx = nearest_tip_to_last_st_first_pt_idx

                        # Get the neighbors of the first (unselected) vert of the closed selection U.
                        vert_neighbors = []
                        for verts in single_unselected_verts_and_neighbors:
                            if verts[0] == nearest_tip_to_last_st_first_pt_idx:
                                vert_neighbors.append(verts[1])
                                vert_neighbors.append(verts[2])
                                break

                        points_first_and_neighbor = []
                        points_first_and_neighbor.append(self.main_object.matrix_world * self.main_object.data.vertices[nearest_tip_to_last_st_first_pt_idx].co)
                        points_first_and_neighbor.append(self.main_object.matrix_world * self.main_object.data.vertices[vert_neighbors[0]].co)

                        points_last_stroke_tips = []
                        points_last_stroke_tips.append(self.main_splines.data.splines[len(self.main_splines.data.splines) - 1].bezier_points[0].co)
                        points_last_stroke_tips.append(self.main_splines.data.splines[len(self.main_splines.data.splines) - 1].bezier_points[1].co)

                        vec_A = points_first_and_neighbor[0] - points_first_and_neighbor[1]
                        vec_B = points_last_stroke_tips[0] - points_last_stroke_tips[1]

                        # Compare the direction of the selection and the last grease pencil stroke to determine which is the vertex neighbor to the first vertex (unselected) of the closed selection. This will determine the direction of the closed selection.
                        if vec_A.dot(vec_B) < 0:
                            first_vert_U2_idx = vert_neighbors[1]
                        else:
                            first_vert_U2_idx = vert_neighbors[0]

                else:
                    self.selection_U2_exists = False

        elif selection_type == "NO_SELECTION":
            self.selection_U_exists = False
            self.selection_V_exists = False



        #### Get an ordered list of the vertices of Selection-U.
        verts_ordered_U = []
        if self.selection_U_exists:
            verts_ordered_U = self.get_ordered_verts(self.main_object, all_selected_edges_idx, all_verts_idx, first_vert_U_idx, middle_vertex_idx, closing_vert_U_idx)
            verts_ordered_U_indices = [x.index for x in verts_ordered_U]

        #### Get an ordered list of the vertices of Selection-U2.
        verts_ordered_U2 = []
        if self.selection_U2_exists:
            verts_ordered_U2 = self.get_ordered_verts(self.main_object, all_selected_edges_idx, all_verts_idx, first_vert_U2_idx, middle_vertex_idx, closing_vert_U2_idx)
            verts_ordered_U2_indices = [x.index for x in verts_ordered_U2]

        #### Get an ordered list of the vertices of Selection-V.
        verts_ordered_V = []
        if self.selection_V_exists:
            verts_ordered_V = self.get_ordered_verts(self.main_object, all_selected_edges_idx, all_verts_idx, first_vert_V_idx, middle_vertex_idx, closing_vert_V_idx)
            verts_ordered_V_indices = [x.index for x in verts_ordered_V]

        #### Get an ordered list of the vertices of Selection-V2.
        verts_ordered_V2 = []
        if self.selection_V2_exists:
            verts_ordered_V2 = self.get_ordered_verts(self.main_object, all_selected_edges_idx, all_verts_idx, first_vert_V2_idx, middle_vertex_idx, closing_vert_V2_idx)
            verts_ordered_V2_indices = [x.index for x in verts_ordered_V2]



        #### Check if when there are two-not-connected selections both have the same number of verts. If not terminate the script.
        if ((self.selection_U2_exists and len(verts_ordered_U) != len(verts_ordered_U2)) or (self.selection_V2_exists and len(verts_ordered_V) != len(verts_ordered_V2))):
            # Display a warning.
            self.report({'WARNING'}, "Both selections must have the same number of edges")

            self.cleanup_on_interruption()

            self.stopping_errors = True

            return{'CANCELLED'}



        #### Calculate edges U proportions.

        # Sum selected edges U lengths.
        edges_lengths_U = []
        edges_lengths_sum_U = 0

        if self.selection_U_exists:
            edges_lengths_U, edges_lengths_sum_U = self.get_chain_length(self.main_object, verts_ordered_U)

        if self.selection_U2_exists:
            edges_lengths_U2, edges_lengths_sum_U2 = self.get_chain_length(self.main_object, verts_ordered_U2)

        # Sum selected edges V lengths.
        edges_lengths_V = []
        edges_lengths_sum_V = 0

        if self.selection_V_exists:
            edges_lengths_V, edges_lengths_sum_V = self.get_chain_length(self.main_object, verts_ordered_V)

        if self.selection_V2_exists:
            edges_lengths_V2, edges_lengths_sum_V2 = self.get_chain_length(self.main_object, verts_ordered_V2)


        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
        bpy.ops.curve.subdivide('INVOKE_REGION_WIN', number_cuts = bpy.context.scene.SURFSK_precision)
        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')


        # Proportions U.
        edges_proportions_U = []
        edges_proportions_U = self.get_edges_proportions(edges_lengths_U, edges_lengths_sum_U, self.selection_U_exists, self.edges_U)
        verts_count_U = len(edges_proportions_U) + 1

        if self.selection_U2_exists:
            edges_proportions_U2 = []
            edges_proportions_U2 = self.get_edges_proportions(edges_lengths_U2, edges_lengths_sum_U2, self.selection_U2_exists, self.edges_V)
            verts_count_U2 = len(edges_proportions_U2) + 1

        # Proportions V.
        edges_proportions_V = []
        edges_proportions_V = self.get_edges_proportions(edges_lengths_V, edges_lengths_sum_V, self.selection_V_exists, self.edges_V)
        verts_count_V = len(edges_proportions_V) + 1

        if self.selection_V2_exists:
            edges_proportions_V2 = []
            edges_proportions_V2 = self.get_edges_proportions(edges_lengths_V2, edges_lengths_sum_V2, self.selection_V2_exists, self.edges_V)
            verts_count_V2 = len(edges_proportions_V2) + 1








        #### Cyclic Follow: simplify sketched curves, make them Cyclic, and complete the actual sketched curves with a "closing segment".
        if self.cyclic_follow and not self.selection_V_exists and not ((self.selection_U_exists and not self.selection_U_is_closed) or (self.selection_U2_exists and not self.selection_U2_is_closed)):
            simplified_spline_coords = []
            simplified_curve = []
            ob_simplified_curve = []
            splines_first_v_co = []
            for i in range(len(self.main_splines.data.splines)):
                # Create a curve object for the actual spline "cyclic extension".
                simplified_curve.append(bpy.data.curves.new('SURFSKIO_simpl_crv', 'CURVE'))
                ob_simplified_curve.append(bpy.data.objects.new('SURFSKIO_simpl_crv', simplified_curve[i]))
                bpy.context.scene.objects.link(ob_simplified_curve[i])

                simplified_curve[i].dimensions = "3D"

                spline_coords = []
                for bp in self.main_splines.data.splines[i].bezier_points:
                    spline_coords.append(bp.co)

                # Simplification.
                simplified_spline_coords.append(self.simplify_spline(spline_coords, 5))

                # Get the coordinates of the first vert of the actual spline.
                splines_first_v_co.append(simplified_spline_coords[i][0])


                # Generate the spline.
                spline = simplified_curve[i].splines.new('BEZIER')
                spline.bezier_points.add(len(simplified_spline_coords[i]) - 1) # less one because one point is added when the spline is created.
                for p in range(0, len(simplified_spline_coords[i])):
                    spline.bezier_points[p].co = simplified_spline_coords[i][p]


                spline.use_cyclic_u = True

                spline_bp_count = len(spline.bezier_points)

                bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
                bpy.data.objects[ob_simplified_curve[i].name].select = True
                bpy.context.scene.objects.active = bpy.context.scene.objects[ob_simplified_curve[i].name]

                bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
                bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='SELECT')
                bpy.ops.curve.handle_type_set('INVOKE_REGION_WIN', type='AUTOMATIC')
                bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')
                bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')


                # Select the "closing segment", and subdivide it.
                ob_simplified_curve[i].data.splines[0].bezier_points[0].select_control_point = True
                ob_simplified_curve[i].data.splines[0].bezier_points[0].select_left_handle = True
                ob_simplified_curve[i].data.splines[0].bezier_points[0].select_right_handle = True

                ob_simplified_curve[i].data.splines[0].bezier_points[spline_bp_count - 1].select_control_point = True
                ob_simplified_curve[i].data.splines[0].bezier_points[spline_bp_count - 1].select_left_handle = True
                ob_simplified_curve[i].data.splines[0].bezier_points[spline_bp_count - 1].select_right_handle = True

                bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
                segments = sqrt((ob_simplified_curve[i].data.splines[0].bezier_points[0].co - ob_simplified_curve[i].data.splines[0].bezier_points[spline_bp_count - 1].co).length / self.average_gp_segment_length)
                for t in range(2):
                    bpy.ops.curve.subdivide('INVOKE_REGION_WIN', number_cuts = segments)


                # Delete the other vertices and make it non-cyclic to keep only the needed verts of the "closing segment".
                bpy.ops.curve.select_all(action = 'INVERT')
                bpy.ops.curve.delete(type='VERT')
                ob_simplified_curve[i].data.splines[0].use_cyclic_u = False
                bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')


                # Add the points of the "closing segment" to the original curve from grease pencil stroke.
                first_new_index = len(self.main_splines.data.splines[i].bezier_points)
                self.main_splines.data.splines[i].bezier_points.add(len(ob_simplified_curve[i].data.splines[0].bezier_points) - 1)
                for t in range(1, len(ob_simplified_curve[i].data.splines[0].bezier_points)):
                    self.main_splines.data.splines[i].bezier_points[t - 1 + first_new_index].co = ob_simplified_curve[i].data.splines[0].bezier_points[t].co


                # Delete the temporal curve.
                bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
                bpy.data.objects[ob_simplified_curve[i].name].select = True
                bpy.context.scene.objects.active = bpy.context.scene.objects[ob_simplified_curve[i].name]

                bpy.ops.object.delete()



        #### Get the coords of the points distributed along the sketched strokes, with proportions-U of the first selection.
        pts_on_strokes_with_proportions_U = self.distribute_pts(self.main_splines.data.splines, edges_proportions_U)

        sketched_splines_parsed = []

        if self.selection_U2_exists:
            # Initialize the multidimensional list with the proportions of all the segments.
            proportions_loops_crossing_strokes = []
            for i in range(len(pts_on_strokes_with_proportions_U)):
                proportions_loops_crossing_strokes.append([])

                for t in range(len(pts_on_strokes_with_proportions_U[0])):
                    proportions_loops_crossing_strokes[i].append(None)


            # Calculate the proportions of each segment of the loops-U from pts_on_strokes_with_proportions_U.
            for lp in range(len(pts_on_strokes_with_proportions_U[0])):
                loop_segments_lengths = []

                for st in range(len(pts_on_strokes_with_proportions_U)):
                    if st == 0: # When on the first stroke, add the segment from the selection to the dirst stroke.
                        loop_segments_lengths.append(((self.main_object.matrix_world * verts_ordered_U[lp].co) - pts_on_strokes_with_proportions_U[0][lp]).length)

                    if st != len(pts_on_strokes_with_proportions_U) - 1: # For all strokes except for the last, calculate the distance from the actual stroke to the next.
                        loop_segments_lengths.append((pts_on_strokes_with_proportions_U[st][lp] - pts_on_strokes_with_proportions_U[st + 1][lp]).length)

                    if st == len(pts_on_strokes_with_proportions_U) - 1: # When on the last stroke, add the segments from the last stroke to the second selection.
                        loop_segments_lengths.append((pts_on_strokes_with_proportions_U[st][lp] - (self.main_object.matrix_world * verts_ordered_U2[lp].co)).length)

                # Calculate full loop length.
                loop_seg_lengths_sum = 0
                for i in range(len(loop_segments_lengths)):
                    loop_seg_lengths_sum += loop_segments_lengths[i]

                # Fill the multidimensional list with the proportions of all the segments.
                for st in range(len(pts_on_strokes_with_proportions_U)):
                    proportions_loops_crossing_strokes[st][lp] = loop_segments_lengths[st] / loop_seg_lengths_sum


            # Calculate proportions for each stroke.
            for st in range(len(pts_on_strokes_with_proportions_U)):
                actual_stroke_spline = []
                actual_stroke_spline.append(self.main_splines.data.splines[st]) # Needs to be a list for the "distribute_pts" method.

                # Calculate the proportions for the actual stroke.
                actual_edges_proportions_U = []
                for i in range(len(edges_proportions_U)):
                    proportions_sum = 0

                    # Sum the proportions of this loop up to the actual.
                    for t in range(0, st + 1):
                        proportions_sum += proportions_loops_crossing_strokes[t][i]

                    actual_edges_proportions_U.append(edges_proportions_U[i] - ((edges_proportions_U[i] - edges_proportions_U2[i]) * proportions_sum))  # i + 1, because proportions_loops_crossing_strokes refers to loops, and the proportions refer to edges, so we start at the element 1 of proportions_loops_crossing_strokes instead of element 0.


                points_actual_spline = self.distribute_pts(actual_stroke_spline, actual_edges_proportions_U)
                sketched_splines_parsed.append(points_actual_spline[0])

        else:
            sketched_splines_parsed = pts_on_strokes_with_proportions_U



        #### If the selection type is "TWO_NOT_CONNECTED" replace the points of the last spline with the points in the "target" selection.
        if selection_type == "TWO_NOT_CONNECTED":
            if self.selection_U2_exists:
                for i in range(0, len(sketched_splines_parsed[len(sketched_splines_parsed) - 1])):
                    sketched_splines_parsed[len(sketched_splines_parsed) - 1][i] = self.main_object.matrix_world * verts_ordered_U2[i].co


        #### Create temporary curves along the "control-points" found on the sketched curves and the mesh selection.
        mesh_ctrl_pts_name = "SURFSKIO_ctrl_pts"
        me = bpy.data.meshes.new(mesh_ctrl_pts_name)
        ob_ctrl_pts = bpy.data.objects.new(mesh_ctrl_pts_name, me)
        ob_ctrl_pts.data = me
        bpy.context.scene.objects.link(ob_ctrl_pts)


        cyclic_loops_U = []
        first_verts = []
        second_verts = []
        last_verts = []
        for i in range(0, verts_count_U):
            vert_num_in_spline = 1

            if self.selection_U_exists:
                ob_ctrl_pts.data.vertices.add(1)
                last_v = ob_ctrl_pts.data.vertices[len(ob_ctrl_pts.data.vertices) - 1]
                last_v.co = self.main_object.matrix_world * verts_ordered_U[i].co

                vert_num_in_spline += 1


            for t in range(0, len(sketched_splines_parsed)):
                ob_ctrl_pts.data.vertices.add(1)
                v = ob_ctrl_pts.data.vertices[len(ob_ctrl_pts.data.vertices) - 1]
                v.co = sketched_splines_parsed[t][i]


                if vert_num_in_spline > 1:
                    ob_ctrl_pts.data.edges.add(1)
                    ob_ctrl_pts.data.edges[len(ob_ctrl_pts.data.edges) - 1].vertices[0] = len(ob_ctrl_pts.data.vertices) - 2
                    ob_ctrl_pts.data.edges[len(ob_ctrl_pts.data.edges) - 1].vertices[1] = len(ob_ctrl_pts.data.vertices) - 1

                if t == 0:
                    first_verts.append(v.index)

                if t == 1:
                    second_verts.append(v.index)

                if t == len(sketched_splines_parsed) - 1:
                    last_verts.append(v.index)


                last_v = v

                vert_num_in_spline += 1


        bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
        bpy.data.objects[ob_ctrl_pts.name].select = True
        bpy.context.scene.objects.active = bpy.data.objects[ob_ctrl_pts.name]

        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
        bpy.ops.mesh.select_all(action='DESELECT')
        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')


        #### Determine which loops-U will be "Cyclic".
        for i in range(0, len(first_verts)):
            if self.automatic_join and not self.cyclic_cross and selection_type != "TWO_CONNECTED" and len(self.main_splines.data.splines) >= 3: # When there is Cyclic Cross there is no need of Automatic Join, (and there are at least three strokes).
                v = ob_ctrl_pts.data.vertices

                first_point_co = v[first_verts[i]].co
                second_point_co = v[second_verts[i]].co
                last_point_co = v[last_verts[i]].co

                # Coordinates of the point in the center of both the first and last verts.
                verts_center_co = [(first_point_co[0] + last_point_co[0]) / 2, (first_point_co[1] + last_point_co[1]) / 2, (first_point_co[2] + last_point_co[2]) / 2]

                vec_A = second_point_co - first_point_co
                vec_B = second_point_co - mathutils.Vector(verts_center_co)


                # Calculate the length of the first segment of the loop, and the length it would have after moving the first vert to the middle position between first and last.
                length_original = (second_point_co - first_point_co).length
                length_target = (second_point_co - mathutils.Vector(verts_center_co)).length

                angle = vec_A.angle(vec_B) / math.pi


                if length_target <= length_original * 1.03 * self.join_stretch_factor and angle <= 0.008 * self.join_stretch_factor and not self.selection_U_exists: # If the target length doesn't stretch too much, and the its angle doesn't change to much either.
                    cyclic_loops_U.append(True)

                    # Move the first vert to the center coordinates.
                    ob_ctrl_pts.data.vertices[first_verts[i]].co = verts_center_co

                    # Select the last verts from Cyclic loops, for later deletion all at once.
                    v[last_verts[i]].select = True

                else:
                    cyclic_loops_U.append(False)

            else:
                if self.cyclic_cross and not self.selection_U_exists and not ((self.selection_V_exists and not self.selection_V_is_closed) or (self.selection_V2_exists and not self.selection_V2_is_closed)): # If "Cyclic Cross" is active then "all" crossing curves become cyclic.
                    cyclic_loops_U.append(True)
                else:
                    cyclic_loops_U.append(False)

        # The cyclic_loops_U list needs to be reversed.
        cyclic_loops_U.reverse()

        # Delete the previously selected (last_)verts.
        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
        bpy.ops.mesh.delete('INVOKE_REGION_WIN', type='VERT')
        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

        # Create curves from control points.
        bpy.ops.object.convert('INVOKE_REGION_WIN', target='CURVE', keep_original=False)
        ob_curves_surf = bpy.context.scene.objects.active
        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
        bpy.ops.curve.spline_type_set('INVOKE_REGION_WIN', type='BEZIER')
        bpy.ops.curve.handle_type_set('INVOKE_REGION_WIN', type='AUTOMATIC')

        # Make Cyclic the splines designated as Cyclic.
        for i in range(0, len(cyclic_loops_U)):
            ob_curves_surf.data.splines[i].use_cyclic_u = cyclic_loops_U[i]


        #### Get the coords of all points on first loop-U, for later comparison with its subdivided version, to know which points of the loops-U are crossed by the original strokes. The indices wiil be the same for the other loops-U.
        if self.loops_on_strokes:
            coords_loops_U_control_points = []
            for p in ob_ctrl_pts.data.splines[0].bezier_points:
                coords_loops_U_control_points.append(["%.4f" % p.co[0], "%.4f" % p.co[1], "%.4f" % p.co[2]])

            tuple(coords_loops_U_control_points)


        # Calculate number of edges-V in case option "Loops on strokes" is active or inactive.
        if self.loops_on_strokes and not self.selection_V_exists:
                edges_V_count = len(self.main_splines.data.splines) * self.edges_V
        else:
            edges_V_count = len(edges_proportions_V)


        # The Follow precision will vary depending on the number of Follow face-loops.
        precision_multiplier = round(2 + (edges_V_count / 15))

        curve_cuts = bpy.context.scene.SURFSK_precision * precision_multiplier

        # Subdivide the curves.
        bpy.ops.curve.subdivide('INVOKE_REGION_WIN', number_cuts = curve_cuts)

        # The verts position shifting that happens with splines subdivision. For later reorder splines points.
        verts_position_shift = curve_cuts + 1

        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')


        # Reorder coordinates of the points of each spline to put the first point of the spline starting at the position it was the first point before sudividing the curve. And make a new curve object per spline (to handle memory better later).
        splines_U_objects = []
        for i in range(len(ob_curves_surf.data.splines)):
            spline_U_curve = bpy.data.curves.new('SURFSKIO_spline_U_' + str(i), 'CURVE')
            ob_spline_U = bpy.data.objects.new('SURFSKIO_spline_U_' + str(i), spline_U_curve)
            bpy.context.scene.objects.link(ob_spline_U)

            spline_U_curve.dimensions = "3D"


            # Add points to the spline in the new curve object.
            ob_spline_U.data.splines.new('BEZIER')
            for t in range(len(ob_curves_surf.data.splines[i].bezier_points)):
                if cyclic_loops_U[i] == True and not self.selection_U_exists: # If the loop is cyclic.
                    if t + verts_position_shift <= len(ob_curves_surf.data.splines[i].bezier_points) - 1:
                        point_index = t + verts_position_shift
                    else:
                        point_index = t + verts_position_shift - len(ob_curves_surf.data.splines[i].bezier_points)
                else:
                    point_index = t

                if t > 0: # to avoid adding the first point since it's added when the spline is created.
                    ob_spline_U.data.splines[0].bezier_points.add(1)
                ob_spline_U.data.splines[0].bezier_points[t].co = ob_curves_surf.data.splines[i].bezier_points[point_index].co


            if cyclic_loops_U[i] == True and not self.selection_U_exists: # If the loop is cyclic.
                # Add a last point at the same location as the first one.
                ob_spline_U.data.splines[0].bezier_points.add(1)
                ob_spline_U.data.splines[0].bezier_points[len(ob_spline_U.data.splines[0].bezier_points) - 1].co = ob_spline_U.data.splines[0].bezier_points[0].co
            else:
                ob_spline_U.data.splines[0].use_cyclic_u = False


            splines_U_objects.append(ob_spline_U)


            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.data.objects[ob_spline_U.name].select = True
            bpy.context.scene.objects.active = bpy.data.objects[ob_spline_U.name]



        #### When option "Loops on strokes" is active each "Cross" loop will have its own proportions according to where the original strokes "touch" them.
        if self.loops_on_strokes:
            # Get the indices of points where the original strokes "touch" loops-U.
            points_U_crossed_by_strokes = []
            for i in range(len(splines_U_objects[0].data.splines[0].bezier_points)):
                bp = splines_U_objects[0].data.splines[0].bezier_points[i]
                if ["%.4f" % bp.co[0], "%.4f" % bp.co[1], "%.4f" % bp.co[2]] in coords_loops_U_control_points:
                    points_U_crossed_by_strokes.append(i)

            # Make a dictionary with the number of the edge, in the selected chain V, corresponding to each stroke.
            edge_order_number_for_splines = {}
            if self.selection_V_exists:
                # For two-connected selections add a first hypothetic stroke at the begining.
                if selection_type == "TWO_CONNECTED":
                    edge_order_number_for_splines[0] = 0


                for i in range(len(self.main_splines.data.splines)):
                    sp = self.main_splines.data.splines[i]
                    v_idx, dist_temp = self.shortest_distance(self.main_object, sp.bezier_points[0].co, verts_ordered_V_indices)

                    edge_idx_in_chain = verts_ordered_V_indices.index(v_idx) # Get the position (edges count) of the vert v_idx in the selected chain V.

                    # For two-connected selections the strokes go after the hypothetic stroke added before, so the index adds one per spline.
                    if selection_type == "TWO_CONNECTED":
                        spline_number = i + 1
                    else:
                        spline_number = i

                    edge_order_number_for_splines[spline_number] = edge_idx_in_chain


                    # Get the first and last verts indices for later comparison.
                    if i == 0:
                        first_v_idx = v_idx
                    elif i == len(self.main_splines.data.splines) - 1:
                        last_v_idx = v_idx


                if self.selection_V_is_closed:
                    # If there is no last stroke on the last vertex (same as first vertex), add a hypothetic spline at last vert order.
                    if first_v_idx != last_v_idx:
                        edge_order_number_for_splines[(len(self.main_splines.data.splines) - 1) + 1] = len(verts_ordered_V_indices) - 1
                    else:
                        if self.cyclic_cross:
                            edge_order_number_for_splines[len(self.main_splines.data.splines) - 1] = len(verts_ordered_V_indices) - 2
                            edge_order_number_for_splines[(len(self.main_splines.data.splines) - 1) + 1] = len(verts_ordered_V_indices) - 1
                        else:
                            edge_order_number_for_splines[len(self.main_splines.data.splines) - 1] = len(verts_ordered_V_indices) - 1



        #### Get the coords of the points distributed along the "crossing curves", with appropriate proportions-V.
        surface_splines_parsed = []
        for i in range(len(splines_U_objects)):
            sp_ob = splines_U_objects[i]
            # If "Loops on strokes" option is active, calculate the proportions for each loop-U.
            if self.loops_on_strokes:
                # Segments distances from stroke to stroke.
                dist = 0
                full_dist = 0
                segments_distances = []
                for t in range(len(sp_ob.data.splines[0].bezier_points)):
                    bp = sp_ob.data.splines[0].bezier_points[t]

                    if t == 0:
                        last_p = bp.co
                    else:
                        actual_p = bp.co
                        dist += (last_p - actual_p).length

                        if t in points_U_crossed_by_strokes:
                            segments_distances.append(dist)
                            full_dist += dist

                            dist = 0

                        last_p = actual_p

                # Calculate Proportions.
                used_edges_proportions_V = []
                for t in range(len(segments_distances)):
                    if self.selection_V_exists:
                        if t == 0:
                            order_number_last_stroke = 0

                        segment_edges_length_V = 0
                        segment_edges_length_V2 = 0
                        for order in range(order_number_last_stroke, edge_order_number_for_splines[t + 1]):
                            segment_edges_length_V += edges_lengths_V[order]
                            if self.selection_V2_exists:
                                segment_edges_length_V2 += edges_lengths_V2[order]


                        for order in range(order_number_last_stroke, edge_order_number_for_splines[t + 1]):
                            # Calculate each "sub-segment" (the ones between each stroke) length.
                            if self.selection_V2_exists:
                                proportion_sub_seg = (edges_lengths_V2[order] - ((edges_lengths_V2[order] - edges_lengths_V[order]) / len(splines_U_objects) * i)) / (segment_edges_length_V2 - (segment_edges_length_V2 - segment_edges_length_V) / len(splines_U_objects) * i)
                                sub_seg_dist = segments_distances[t] * proportion_sub_seg
                            else:
                                proportion_sub_seg = edges_lengths_V[order] / segment_edges_length_V
                                sub_seg_dist = segments_distances[t] * proportion_sub_seg

                            used_edges_proportions_V.append(sub_seg_dist / full_dist)

                        order_number_last_stroke = edge_order_number_for_splines[t + 1]

                    else:
                        for c in range(self.edges_V):
                            # Calculate each "sub-segment" (the ones between each stroke) length.
                            sub_seg_dist = segments_distances[t] / self.edges_V
                            used_edges_proportions_V.append(sub_seg_dist / full_dist)

                actual_spline = self.distribute_pts(sp_ob.data.splines, used_edges_proportions_V)
                surface_splines_parsed.append(actual_spline[0])

            else:
                if self.selection_V2_exists:
                    used_edges_proportions_V = []
                    for p in range(len(edges_proportions_V)):
                        used_edges_proportions_V.append(edges_proportions_V2[p] - ((edges_proportions_V2[p] - edges_proportions_V[p]) / len(splines_U_objects) * i))
                else:
                    used_edges_proportions_V = edges_proportions_V

                actual_spline = self.distribute_pts(sp_ob.data.splines, used_edges_proportions_V)
                surface_splines_parsed.append(actual_spline[0])




        # Set the verts of the first and last splines to the locations of the respective verts in the selections.
        if self.selection_V_exists:
            for i in range(0, len(surface_splines_parsed[0])):
                surface_splines_parsed[len(surface_splines_parsed) - 1][i] = self.main_object.matrix_world * verts_ordered_V[i].co

        if selection_type == "TWO_NOT_CONNECTED":
            if self.selection_V2_exists:
                for i in range(0, len(surface_splines_parsed[0])):
                    surface_splines_parsed[0][i] = self.main_object.matrix_world * verts_ordered_V2[i].co




        # When "Automatic join" option is active (and the selection type is not "TWO_CONNECTED"), merge the verts of the tips of the loops when they are "near enough".
        if self.automatic_join and selection_type != "TWO_CONNECTED":
            #### Join the tips of "Follow" loops that are near enough and must be "closed".
            if not self.selection_V_exists and len(edges_proportions_U) >= 3:
                for i in range(len(surface_splines_parsed[0])):
                    sp = surface_splines_parsed
                    loop_segment_dist = (sp[0][i] - sp[1][i]).length
                    full_loop_dist = loop_segment_dist * self.edges_U

                    verts_middle_position_co = [(sp[0][i][0] + sp[len(sp) - 1][i][0]) / 2, (sp[0][i][1] + sp[len(sp) - 1][i][1]) / 2, (sp[0][i][2] + sp[len(sp) - 1][i][2]) / 2]

                    points_original = []
                    points_original.append(sp[1][i])
                    points_original.append(sp[0][i])

                    points_target = []
                    points_target.append(sp[1][i])
                    points_target.append(mathutils.Vector(verts_middle_position_co))

                    vec_A = points_original[0] - points_original[1]
                    vec_B = points_target[0] - points_target[1]


                    angle = vec_A.angle(vec_B) / math.pi

                    edge_new_length = (mathutils.Vector(verts_middle_position_co) - sp[1][i]).length

                    if edge_new_length <= loop_segment_dist * 1.5 * self.join_stretch_factor and angle < 0.25 * self.join_stretch_factor: # If after moving the verts to the middle point, the segment doesn't stretch too much.
                        if not (self.selection_U_exists and i == 0) and not (self.selection_U2_exists and i == len(surface_splines_parsed[0]) - 1): # Avoid joining when the actual loop must be merged with the original mesh.
                            # Change the coords of both verts to the middle position.
                            surface_splines_parsed[0][i] = verts_middle_position_co
                            surface_splines_parsed[len(surface_splines_parsed) - 1][i] = verts_middle_position_co



        #### Delete object with control points and object from grease pencil convertion.
        bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
        bpy.data.objects[ob_ctrl_pts.name].select = True
        bpy.context.scene.objects.active = bpy.data.objects[ob_ctrl_pts.name]

        bpy.ops.object.delete()


        for sp_ob in splines_U_objects:
            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.data.objects[sp_ob.name].select = True
            bpy.context.scene.objects.active = bpy.data.objects[sp_ob.name]

            bpy.ops.object.delete()




        #### Generate surface.

        # Get all verts coords.
        all_surface_verts_co = []
        for i in range(0, len(surface_splines_parsed)):
            # Get coords of all verts and make a list with them
            for pt_co in surface_splines_parsed[i]:
                all_surface_verts_co.append(pt_co)


        # Define verts for each face.
        all_surface_faces = []
        for i in range(0, len(all_surface_verts_co) - len(surface_splines_parsed[0])):
            if ((i + 1) / len(surface_splines_parsed[0]) != int((i + 1) / len(surface_splines_parsed[0]))):
                all_surface_faces.append([i+1, i , i + len(surface_splines_parsed[0]), i + len(surface_splines_parsed[0]) + 1])


        # Build the mesh.
        surf_me_name = "SURFSKIO_surface"
        me_surf = bpy.data.meshes.new(surf_me_name)

        me_surf.from_pydata(all_surface_verts_co, [], all_surface_faces)

        me_surf.update()

        ob_surface = bpy.data.objects.new(surf_me_name, me_surf)
        bpy.context.scene.objects.link(ob_surface)


        # Select all the "unselected but participating" verts, from closed selection or double selections with middle-vertex, for later join with remove doubles.
        for v_idx in single_unselected_verts:
            self.main_object.data.vertices[v_idx].select = True


        #### Join the new mesh to the main object.
        ob_surface.select = True
        self.main_object.select = True
        bpy.context.scene.objects.active = bpy.data.objects[self.main_object.name]

        bpy.ops.object.join('INVOKE_REGION_WIN')

        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

        bpy.ops.mesh.remove_doubles('INVOKE_REGION_WIN', threshold=0.0001)
        bpy.ops.mesh.normals_make_consistent('INVOKE_REGION_WIN', inside=False)
        bpy.ops.mesh.select_all('INVOKE_REGION_WIN', action='DESELECT')



        return{'FINISHED'}



    def execute(self, context):
#        self.initial_global_undo_state = bpy.context.user_preferences.edit.use_global_undo

        bpy.context.user_preferences.edit.use_global_undo = False

        if not self.is_fill_faces:
            bpy.ops.wm.context_set_value(data_path='tool_settings.mesh_select_mode', value='True, False, False')

            # Build splines from the "last saved splines".
            last_saved_curve = bpy.data.curves.new('SURFSKIO_last_crv', 'CURVE')
            self.main_splines = bpy.data.objects.new('SURFSKIO_last_crv', last_saved_curve)
            bpy.context.scene.objects.link(self.main_splines)

            last_saved_curve.dimensions = "3D"

            for sp in self.last_strokes_splines_coords:
                spline = self.main_splines.data.splines.new('BEZIER')
                spline.bezier_points.add(len(sp) - 1) # less one because one point is added when the spline is created.
                for p in range(0, len(sp)):
                    spline.bezier_points[p].co = [sp[p][0], sp[p][1], sp[p][2]]


            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.data.objects[self.main_splines.name].select = True
            bpy.context.scene.objects.active = bpy.data.objects[self.main_splines.name]

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='SELECT')
            bpy.ops.curve.handle_type_set(type='VECTOR') # Important to make it vector first and then automatic, otherwise the tips handles get too big and distort the shrinkwrap results later.
            bpy.ops.curve.handle_type_set('INVOKE_REGION_WIN', type='AUTOMATIC')
            bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')


            self.main_splines.name = "SURFSKIO_temp_strokes"


            if self.is_crosshatch:
                strokes_for_crosshatch = True
                strokes_for_rectangular_surface = False
            else:
                strokes_for_rectangular_surface = True
                strokes_for_crosshatch = False


            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.data.objects[self.main_object.name].select = True
            bpy.context.scene.objects.active = bpy.data.objects[self.main_object.name]

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')


            if strokes_for_rectangular_surface:
                self.rectangular_surface()
            elif strokes_for_crosshatch:
                self.crosshatch_surface_execute()


            #### Delete main splines
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.data.objects[self.main_splines.name].select = True
            bpy.context.scene.objects.active = bpy.data.objects[self.main_splines.name]

            bpy.ops.object.delete()

            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.data.objects[self.main_object.name].select = True
            bpy.context.scene.objects.active = bpy.data.objects[self.main_object.name]

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')


        bpy.context.user_preferences.edit.use_global_undo = self.initial_global_undo_state

        return{'FINISHED'}



    def invoke(self, context, event):
        self.initial_global_undo_state = bpy.context.user_preferences.edit.use_global_undo

        self.main_object = bpy.context.scene.objects.active
        self.main_object_selected_verts_count = int(self.main_object.data.total_vert_sel)


        bpy.context.user_preferences.edit.use_global_undo = False


        bpy.ops.wm.context_set_value(data_path='tool_settings.mesh_select_mode', value='True, False, False')

        # Out Edit mode and In again to make sure the actual mesh selections are being taken.
        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')



        self.cyclic_cross = bpy.context.scene.SURFSK_cyclic_cross
        self.cyclic_follow = bpy.context.scene.SURFSK_cyclic_follow
        self.automatic_join = bpy.context.scene.SURFSK_automatic_join
        self.loops_on_strokes = bpy.context.scene.SURFSK_loops_on_strokes
        self.keep_strokes = bpy.context.scene.SURFSK_keep_strokes

        self.edges_U = 5

        if self.loops_on_strokes:
            self.edges_V = 1
        else:
            self.edges_V = 5

        self.is_fill_faces = False

        self.stopping_errors = False

        self.last_strokes_splines_coords = []


        #### Determine the type of the strokes.
        self.strokes_type = get_strokes_type(self.main_object)

        #### Check if it will be used grease pencil strokes or curves.
        if self.strokes_type == "GP_STROKES" or self.strokes_type == "EXTERNAL_CURVE": # If there are strokes to be used.
            if self.strokes_type == "GP_STROKES":
                # Convert grease pencil strokes to curve.
                bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
                bpy.ops.gpencil.convert('INVOKE_REGION_WIN', type='CURVE', use_link_strokes=False)
                # XXX gpencil.convert now keep org object as active/selected, *not* newly created curve!
                # XXX This is far from perfect, but should work in most cases...
#                self.original_curve = bpy.context.object
                for ob in bpy.context.selected_objects:
                    if ob != bpy.context.scene.objects.active and ob.name.startswith("GP_Layer"):
                        self.original_curve = ob
                self.using_external_curves = False
            elif self.strokes_type == "EXTERNAL_CURVE":
                for ob in bpy.context.selected_objects:
                    if ob != bpy.context.scene.objects.active:
                        self.original_curve = ob
                self.using_external_curves = True

                bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')


            #### Make sure there are no objects left from erroneous executions of this operator, with the reserved names used here.
            for o in bpy.data.objects:
                if o.name.find("SURFSKIO_") != -1:
                    bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
                    bpy.data.objects[o.name].select = True
                    bpy.context.scene.objects.active = bpy.data.objects[o.name]

                    bpy.ops.object.delete()


            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.data.objects[self.original_curve.name].select = True
            bpy.context.scene.objects.active = bpy.data.objects[self.original_curve.name]

            bpy.ops.object.duplicate('INVOKE_REGION_WIN')


            self.temporary_curve = bpy.context.scene.objects.active


            # Deselect all points of the curve
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
            bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')



            # Delete splines with only a single isolated point.
            for i in range(len(self.temporary_curve.data.splines)):
                sp = self.temporary_curve.data.splines[i]

                if len(sp.bezier_points) == 1:
                    sp.bezier_points[0].select_control_point = True

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
            bpy.ops.curve.delete(type='VERT')
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')


            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.data.objects[self.temporary_curve.name].select = True
            bpy.context.scene.objects.active = bpy.data.objects[self.temporary_curve.name]

            #### Set a minimum number of points for crosshatch
            minimum_points_num = 15

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
            # Check if the number of points of each curve has at least the number of points of minimum_points_num, which is a bit more than the face-loops limit. If not, subdivide to reach at least that number of ponts.
            for i in range(len(self.temporary_curve.data.splines)):
                sp = self.temporary_curve.data.splines[i]

                if len(sp.bezier_points) < minimum_points_num:
                    for bp in sp.bezier_points:
                        bp.select_control_point = True

                    if (len(sp.bezier_points) - 1) != 0:
                        subdivide_cuts = int((minimum_points_num - len(sp.bezier_points)) / (len(sp.bezier_points) - 1)) + 1 # Formula to get the number of cuts that will make a curve of N number of points have near to "minimum_points_num" points, when subdividing with this number of cuts.
                    else:
                        subdivide_cuts = 0


                    bpy.ops.curve.subdivide('INVOKE_REGION_WIN', number_cuts = subdivide_cuts)
                    bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')



            # Detect if the strokes are a crosshatch and do it if it is.
            self.crosshatch_surface_invoke(self.temporary_curve)



            if not self.is_crosshatch:
                bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
                bpy.data.objects[self.temporary_curve.name].select = True
                bpy.context.scene.objects.active = bpy.data.objects[self.temporary_curve.name]

                bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

                #### Set a minimum number of points for rectangular surfaces.
                minimum_points_num = 60

                # Check if the number of points of each curve has at least the number of points of minimum_points_num, which is a bit more than the face-loops limit. If not, subdivide to reach at least that number of ponts.
                for i in range(len(self.temporary_curve.data.splines)):
                    sp = self.temporary_curve.data.splines[i]

                    if len(sp.bezier_points) < minimum_points_num:
                        for bp in sp.bezier_points:
                            bp.select_control_point = True

                        if (len(sp.bezier_points) - 1) != 0:
                            subdivide_cuts = int((minimum_points_num - len(sp.bezier_points)) / (len(sp.bezier_points) - 1)) + 1 # Formula to get the number of cuts that will make a curve of N number of points have near to "minimum_points_num" points, when subdividing with this number of cuts.
                        else:
                            subdivide_cuts = 0


                        bpy.ops.curve.subdivide('INVOKE_REGION_WIN', number_cuts = subdivide_cuts)
                        bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')

                bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')




            # Save coordinates of the actual strokes (as the "last saved splines").
            for sp_idx in range(len(self.temporary_curve.data.splines)):
                self.last_strokes_splines_coords.append([])
                for bp_idx in range(len(self.temporary_curve.data.splines[sp_idx].bezier_points)):
                    coords = self.temporary_curve.matrix_world * self.temporary_curve.data.splines[sp_idx].bezier_points[bp_idx].co
                    self.last_strokes_splines_coords[sp_idx].append([coords[0], coords[1], coords[2]])


            # Check for cyclic splines, put the first and last points in the middle of their actual positions.
            for sp_idx in range(len(self.temporary_curve.data.splines)):
                if self.temporary_curve.data.splines[sp_idx].use_cyclic_u == True:
                    first_p_co = self.last_strokes_splines_coords[sp_idx][0]
                    last_p_co = self.last_strokes_splines_coords[sp_idx][len(self.last_strokes_splines_coords[sp_idx]) - 1]

                    target_co = [(first_p_co[0] + last_p_co[0]) / 2, (first_p_co[1] + last_p_co[1]) / 2, (first_p_co[2] + last_p_co[2]) / 2]

                    self.last_strokes_splines_coords[sp_idx][0] = target_co
                    self.last_strokes_splines_coords[sp_idx][len(self.last_strokes_splines_coords[sp_idx]) - 1] = target_co

            tuple(self.last_strokes_splines_coords)



            # Estimation of the average length of the segments between each point of the grease pencil strokes. Will be useful to determine whether a curve should be made "Cyclic".
            segments_lengths_sum = 0
            segments_count = 0
            random_spline = self.temporary_curve.data.splines[0].bezier_points
            for i in range(0, len(random_spline)):
                if i != 0 and len(random_spline) - 1 >= i:
                    segments_lengths_sum += (random_spline[i - 1].co - random_spline[i].co).length
                    segments_count += 1

            self.average_gp_segment_length = segments_lengths_sum / segments_count


            #### Delete temporary strokes curve object
            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.data.objects[self.temporary_curve.name].select = True
            bpy.context.scene.objects.active = bpy.data.objects[self.temporary_curve.name]

            bpy.ops.object.delete()


            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.data.objects[self.main_object.name].select = True
            bpy.context.scene.objects.active = bpy.data.objects[self.main_object.name]

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')


            self.execute(context)
            bpy.context.user_preferences.edit.use_global_undo = False # Set again since "execute()" will turn it again to its initial value.


            #### If "Keep strokes" option is not active, delete original strokes curve object.
            if (not self.stopping_errors and not self.keep_strokes) or self.is_crosshatch:
                bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
                bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
                bpy.data.objects[self.original_curve.name].select = True
                bpy.context.scene.objects.active = bpy.data.objects[self.original_curve.name]

                bpy.ops.object.delete()

                bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
                bpy.data.objects[self.main_object.name].select = True
                bpy.context.scene.objects.active = bpy.data.objects[self.main_object.name]

                bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')



            #### Delete grease pencil strokes.
            if self.strokes_type == "GP_STROKES" and not self.stopping_errors:
                bpy.ops.gpencil.active_frame_delete('INVOKE_REGION_WIN')


            bpy.context.user_preferences.edit.use_global_undo = self.initial_global_undo_state


            if not self.stopping_errors:
                return {"FINISHED"}
            else:
                return{"CANCELLED"}

        elif self.strokes_type == "SELECTION_ALONE":
            self.is_fill_faces = True

            created_faces_count = self.fill_with_faces(self.main_object)

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            bpy.context.user_preferences.edit.use_global_undo = self.initial_global_undo_state

            if created_faces_count == 0:
                self.report({'WARNING'}, "There aren't any strokes attatched to the object")
                return {"CANCELLED"}
            else:
                return {"FINISHED"}


        bpy.context.user_preferences.edit.use_global_undo = self.initial_global_undo_state

        if self.strokes_type == "EXTERNAL_NO_CURVE":
            self.report({'WARNING'}, "The secondary object is not a Curve.")
            return{"CANCELLED"}

        elif self.strokes_type == "MORE_THAN_ONE_EXTERNAL":
            self.report({'WARNING'}, "There shouldn't be more than one secondary object selected.")
            return{"CANCELLED"}

        elif self.strokes_type == "SINGLE_GP_STROKE_NO_SELECTION" or self.strokes_type == "SINGLE_CURVE_STROKE_NO_SELECTION":
            self.report({'WARNING'}, "It's needed at least one stroke and one selection, or two strokes.")
            return{"CANCELLED"}

        elif self.strokes_type == "NO_STROKES":
            self.report({'WARNING'}, "There aren't any strokes attatched to the object")
            return{"CANCELLED"}

        elif self.strokes_type == "CURVE_WITH_NON_BEZIER_SPLINES":
            self.report({'WARNING'}, "All splines must be Bezier.")
            return{"CANCELLED"}

        else:
            return{"CANCELLED"}


# Edit strokes operator.
class GPENCIL_OT_SURFSK_edit_strokes(bpy.types.Operator):
    bl_idname = "gpencil.surfsk_edit_strokes"
    bl_label = "Bsurfaces edit strokes"
    bl_description = "Edit the grease pencil strokes or curves used"


    def execute(self, context):
        #### Determine the type of the strokes.
        self.strokes_type = get_strokes_type(self.main_object)
        #### Check if strokes are grease pencil strokes or a curves object.
        selected_objs = bpy.context.selected_objects
        if self.strokes_type == "EXTERNAL_CURVE" or self.strokes_type == "SINGLE_CURVE_STROKE_NO_SELECTION":
            for ob in selected_objs:
                if ob != bpy.context.scene.objects.active:
                    curve_ob = ob

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.data.objects[curve_ob.name].select = True
            bpy.context.scene.objects.active = bpy.data.objects[curve_ob.name]

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
        elif self.strokes_type == "GP_STROKES" or self.strokes_type == "SINGLE_GP_STROKE_NO_SELECTION":
            #### Convert grease pencil strokes to curve.
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
            bpy.ops.gpencil.convert('INVOKE_REGION_WIN', type='CURVE', use_link_strokes=False)
            for ob in bpy.context.selected_objects:
                    if ob != bpy.context.scene.objects.active and ob.name.startswith("GP_Layer"):
                        ob_gp_strokes = ob

            #ob_gp_strokes = bpy.context.object

            #### Delete grease pencil strokes.
            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.data.objects[self.main_object.name].select = True
            bpy.context.scene.objects.active = bpy.data.objects[self.main_object.name]

            bpy.ops.gpencil.active_frame_delete('INVOKE_REGION_WIN')


            #### Clean up curves.
            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.data.objects[ob_gp_strokes.name].select = True
            bpy.context.scene.objects.active = bpy.data.objects[ob_gp_strokes.name]

            curve_crv = ob_gp_strokes.data
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
            bpy.ops.curve.spline_type_set('INVOKE_REGION_WIN', type="BEZIER")
            bpy.ops.curve.handle_type_set('INVOKE_REGION_WIN', type="AUTOMATIC")
            bpy.data.curves[curve_crv.name].show_handles = False
            bpy.data.curves[curve_crv.name].show_normal_face = False

        elif self.strokes_type == "EXTERNAL_NO_CURVE":
            self.report({'WARNING'}, "The secondary object is not a Curve.")
            return{"CANCELLED"}
        elif self.strokes_type == "MORE_THAN_ONE_EXTERNAL":
            self.report({'WARNING'}, "There shouldn't be more than one secondary object selected.")
            return{"CANCELLED"}
        elif self.strokes_type == "NO_STROKES" or self.strokes_type == "SELECTION_ALONE":
            self.report({'WARNING'}, "There aren't any strokes attatched to the object")
            return{"CANCELLED"}
        else:
            return{"CANCELLED"}



    def invoke (self, context, event):
        self.main_object = bpy.context.object

        self.execute(context)

        return {"FINISHED"}


class CURVE_OT_SURFSK_reorder_splines(bpy.types.Operator):
    bl_idname = "curve.surfsk_reorder_splines"
    bl_label = "Bsurfaces reorder splines"
    bl_description = "Defines the order of the splines by using grease pencil strokes"
    bl_options = {'REGISTER', 'UNDO'}

    def execute(self, context):
        objects_to_delete = []
        #### Convert grease pencil strokes to curve.
        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
        bpy.ops.gpencil.convert('INVOKE_REGION_WIN', type='CURVE', use_link_strokes=False)
        for ob in bpy.context.selected_objects:
            if ob != bpy.context.scene.objects.active and ob.name.startswith("GP_Layer"):
                GP_strokes_curve = ob

        #GP_strokes_curve = bpy.context.object
        objects_to_delete.append(GP_strokes_curve)

        bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
        bpy.data.objects[GP_strokes_curve.name].select = True
        bpy.context.scene.objects.active = bpy.data.objects[GP_strokes_curve.name]


        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
        bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='SELECT')
        bpy.ops.curve.subdivide('INVOKE_REGION_WIN', number_cuts = 100)
        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

        bpy.ops.object.duplicate('INVOKE_REGION_WIN')
        GP_strokes_mesh = bpy.context.object
        objects_to_delete.append(GP_strokes_mesh)

        GP_strokes_mesh.data.resolution_u = 1
        bpy.ops.object.convert(target='MESH', keep_original=False)


        bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
        bpy.data.objects[self.main_curve.name].select = True
        bpy.context.scene.objects.active = bpy.data.objects[self.main_curve.name]

        bpy.ops.object.duplicate('INVOKE_REGION_WIN')
        curves_duplicate_1 = bpy.context.object
        objects_to_delete.append(curves_duplicate_1)



        minimum_points_num = 500


        for x in range(round(minimum_points_num / 100)): # Some iterations since the subdivision operator has a limit of 100 subdivisions per iteration.
            #### Check if the number of points of each curve has at least the number of points of minimum_points_num. If not, subdivide to reach at least that number of ponts.
            for i in range(len(curves_duplicate_1.data.splines)):
                sp = curves_duplicate_1.data.splines[i]

                if len(sp.bezier_points) < minimum_points_num:
                    for bp in sp.bezier_points:
                        bp.select_control_point = True

                    if (len(sp.bezier_points) - 1) != 0:
                        subdivide_cuts = int((minimum_points_num - len(sp.bezier_points)) / (len(sp.bezier_points) - 1)) + 1 # Formula to get the number of cuts that will make a curve of N number of points have near to "minimum_points_num" points, when subdividing with this number of cuts.
                    else:
                        subdivide_cuts = 0

                    bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
                    bpy.ops.curve.subdivide('INVOKE_REGION_WIN', number_cuts = subdivide_cuts)
                    bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')
                    bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')


        bpy.ops.object.duplicate('INVOKE_REGION_WIN')
        curves_duplicate_2 = bpy.context.object
        objects_to_delete.append(curves_duplicate_2)


        #### Duplicate the duplicate and add Shrinkwrap to it, with the grease pencil strokes curve as target.
        bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
        bpy.data.objects[curves_duplicate_2.name].select = True
        bpy.context.scene.objects.active = bpy.data.objects[curves_duplicate_2.name]

        bpy.ops.object.modifier_add('INVOKE_REGION_WIN', type='SHRINKWRAP')
        curves_duplicate_2.modifiers["Shrinkwrap"].wrap_method = "NEAREST_VERTEX"
        curves_duplicate_2.modifiers["Shrinkwrap"].target = GP_strokes_mesh
        bpy.ops.object.modifier_apply('INVOKE_REGION_WIN', apply_as='DATA', modifier='Shrinkwrap')


        #### Get the distance of each vert from its original position to its position with Shrinkwrap.
        nearest_points_coords = {}
        for st_idx in range(len(curves_duplicate_1.data.splines)):
            for bp_idx in range(len(curves_duplicate_1.data.splines[st_idx].bezier_points)):
                bp_1_co = curves_duplicate_1.matrix_world * curves_duplicate_1.data.splines[st_idx].bezier_points[bp_idx].co
                bp_2_co = curves_duplicate_2.matrix_world * curves_duplicate_2.data.splines[st_idx].bezier_points[bp_idx].co

                if bp_idx == 0:
                    shortest_dist = (bp_1_co - bp_2_co).length
                    nearest_points_coords[st_idx] = ("%.4f" % bp_2_co[0], "%.4f" % bp_2_co[1], "%.4f" % bp_2_co[2])

                dist = (bp_1_co - bp_2_co).length

                if dist < shortest_dist:
                    nearest_points_coords[st_idx] = ("%.4f" % bp_2_co[0], "%.4f" % bp_2_co[1], "%.4f" % bp_2_co[2])
                    shortest_dist = dist



        #### Get all coords of GP strokes points, for comparison.
        GP_strokes_coords = []
        for st_idx in range(len(GP_strokes_curve.data.splines)):
            GP_strokes_coords.append([("%.4f" % x if "%.4f" % x != "-0.00" else "0.00", "%.4f" % y if "%.4f" % y != "-0.00" else "0.00", "%.4f" % z if "%.4f" % z != "-0.00" else "0.00") for x, y, z in [bp.co for bp in GP_strokes_curve.data.splines[st_idx].bezier_points]])


        #### Check the point of the GP strokes with the same coords as the nearest points of the curves (with shrinkwrap).
        GP_connection_points = {} # Dictionary with GP stroke index as index, and a list as value. The list has as index the point index of the GP stroke nearest to the spline, and as value the spline index.
        for gp_st_idx in range(len(GP_strokes_coords)):
            GPvert_spline_relationship = {}

            for splines_st_idx in range(len(nearest_points_coords)):
                if nearest_points_coords[splines_st_idx] in GP_strokes_coords[gp_st_idx]:
                    GPvert_spline_relationship[GP_strokes_coords[gp_st_idx].index(nearest_points_coords[splines_st_idx])] = splines_st_idx


            GP_connection_points[gp_st_idx] = GPvert_spline_relationship


        #### Get the splines new order.
        splines_new_order = []
        for i in GP_connection_points:
            dict_keys = sorted(GP_connection_points[i].keys()) # Sort dictionaries by key

            for k in dict_keys:
                splines_new_order.append(GP_connection_points[i][k])



        #### Reorder.

        curve_original_name = self.main_curve.name

        bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
        bpy.data.objects[self.main_curve.name].select = True
        bpy.context.scene.objects.active = bpy.data.objects[self.main_curve.name]

        self.main_curve.name = "SURFSKIO_CRV_ORD"

        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
        bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')
        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')


        for sp_idx in range(len(self.main_curve.data.splines)):
            self.main_curve.data.splines[0].bezier_points[0].select_control_point = True

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
            bpy.ops.curve.separate('EXEC_REGION_WIN')
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')



        #### Get the names of the separated splines objects in the original order.
        splines_unordered = {}
        for o in bpy.data.objects:
            if o.name.find("SURFSKIO_CRV_ORD") != -1:
                spline_order_string = o.name.partition(".")[2]

                if spline_order_string != "" and int(spline_order_string) > 0:
                    spline_order_index = int(spline_order_string) - 1
                    splines_unordered[spline_order_index] = o.name



        #### Join all splines objects in final order.
        for order_idx in splines_new_order:
            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.data.objects[splines_unordered[order_idx]].select = True
            bpy.data.objects["SURFSKIO_CRV_ORD"].select = True
            bpy.context.scene.objects.active = bpy.data.objects["SURFSKIO_CRV_ORD"]

            bpy.ops.object.join('INVOKE_REGION_WIN')


        #### Go back to the original name of the curves object.
        bpy.context.object.name = curve_original_name


        #### Delete all unused objects.
        for o in objects_to_delete:
            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.data.objects[o.name].select = True
            bpy.context.scene.objects.active = bpy.data.objects[o.name]

            bpy.ops.object.delete()


        bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
        bpy.data.objects[curve_original_name].select = True
        bpy.context.scene.objects.active = bpy.data.objects[curve_original_name]

        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
        bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')


        bpy.ops.gpencil.active_frame_delete('INVOKE_REGION_WIN')



        return {"FINISHED"}



    def invoke (self, context, event):
        self.main_curve = bpy.context.object


        there_are_GP_strokes = False
        try:
            #### Get the active grease pencil layer.
            strokes_num = len(self.main_curve.grease_pencil.layers.active.active_frame.strokes)

            if strokes_num > 0:
                there_are_GP_strokes = True
        except:
            pass


        if there_are_GP_strokes:
            self.execute(context)
            self.report({'INFO'}, "Splines have been reordered.")
        else:
            self.report({'WARNING'}, "Draw grease pencil strokes to connect splines.")

        return {"FINISHED"}




class CURVE_OT_SURFSK_first_points(bpy.types.Operator):
    bl_idname = "curve.surfsk_first_points"
    bl_label = "Bsurfaces set first points"
    bl_description = "Set the selected points as the first point of each spline"
    bl_options = {'REGISTER', 'UNDO'}



    def execute(self, context):
        splines_to_invert = []

        #### Check non-cyclic splines to invert.
        for i in range(len(self.main_curve.data.splines)):
            b_points = self.main_curve.data.splines[i].bezier_points

            if not i in self.cyclic_splines: # Only for non-cyclic splines
                if b_points[len(b_points) - 1].select_control_point:
                    splines_to_invert.append(i)


        #### Reorder points of cyclic splines, and set all handles to "Automatic".

        # Check first selected point.
        cyclic_splines_new_first_pt = {}
        for i in self.cyclic_splines:
            sp = self.main_curve.data.splines[i]

            for t in range(len(sp.bezier_points)):
                bp = sp.bezier_points[t]
                if bp.select_control_point or bp.select_right_handle or bp.select_left_handle:
                    cyclic_splines_new_first_pt[i] = t
                    break # To take only one if there are more.

        # Reorder.
        for spline_idx in cyclic_splines_new_first_pt:
            sp = self.main_curve.data.splines[spline_idx]

            spline_old_coords = []
            for bp_old in sp.bezier_points:
                coords = (bp_old.co[0], bp_old.co[1], bp_old.co[2])

                left_handle_type = str(bp_old.handle_left_type)
                left_handle_length = float(bp_old.handle_left.length)
                left_handle_xyz = (float(bp_old.handle_left.x), float(bp_old.handle_left.y), float(bp_old.handle_left.z))

                right_handle_type = str(bp_old.handle_right_type)
                right_handle_length = float(bp_old.handle_right.length)
                right_handle_xyz = (float(bp_old.handle_right.x), float(bp_old.handle_right.y), float(bp_old.handle_right.z))

                spline_old_coords.append([coords, left_handle_type, right_handle_type, left_handle_length, right_handle_length, left_handle_xyz, right_handle_xyz])


            for t in range(len(sp.bezier_points)):
                bp = sp.bezier_points

                if t + cyclic_splines_new_first_pt[spline_idx] + 1 <= len(bp) - 1:
                    new_index = t + cyclic_splines_new_first_pt[spline_idx] + 1
                else:
                    new_index = t + cyclic_splines_new_first_pt[spline_idx] + 1 - len(bp)

                bp[t].co = mathutils.Vector(spline_old_coords[new_index][0])

                bp[t].handle_left.length = spline_old_coords[new_index][3]
                bp[t].handle_right.length = spline_old_coords[new_index][4]

                bp[t].handle_left_type = "FREE"
                bp[t].handle_right_type = "FREE"

                bp[t].handle_left.x = spline_old_coords[new_index][5][0]
                bp[t].handle_left.y = spline_old_coords[new_index][5][1]
                bp[t].handle_left.z = spline_old_coords[new_index][5][2]

                bp[t].handle_right.x = spline_old_coords[new_index][6][0]
                bp[t].handle_right.y = spline_old_coords[new_index][6][1]
                bp[t].handle_right.z = spline_old_coords[new_index][6][2]

                bp[t].handle_left_type = spline_old_coords[new_index][1]
                bp[t].handle_right_type = spline_old_coords[new_index][2]



        #### Invert the non-cyclic splines designated above.
        for i in range(len(splines_to_invert)):
            bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
            self.main_curve.data.splines[splines_to_invert[i]].bezier_points[0].select_control_point = True
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            bpy.ops.curve.switch_direction()

        bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')


        #### Keep selected the first vert of each spline.
        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
        for i in range(len(self.main_curve.data.splines)):
            if not self.main_curve.data.splines[i].use_cyclic_u:
                bp = self.main_curve.data.splines[i].bezier_points[0]
            else:
                bp = self.main_curve.data.splines[i].bezier_points[len(self.main_curve.data.splines[i].bezier_points) - 1]

            bp.select_control_point = True
            bp.select_right_handle = True
            bp.select_left_handle = True
        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')




        return {'FINISHED'}



    def invoke (self, context, event):
        self.main_curve = bpy.context.object

        # Check if all curves are Bezier, and detect which ones are cyclic.
        self.cyclic_splines = []
        for i in range(len(self.main_curve.data.splines)):
            if self.main_curve.data.splines[i].type != "BEZIER":
                self.report({'WARNING'}, 'All splines must be Bezier type.')

                return {'CANCELLED'}
            else:
                if self.main_curve.data.splines[i].use_cyclic_u:
                    self.cyclic_splines.append(i)



        self.execute(context)
        self.report({'INFO'}, "First points have been set.")

        return {'FINISHED'}

## Addons Preferences Update Panel
def update_panel(self, context):
    try:
        bpy.utils.unregister_class(VIEW3D_PT_tools_SURFSK_mesh)
        bpy.utils.unregister_class(VIEW3D_PT_tools_SURFSK_curve)
    except:
        pass
    VIEW3D_PT_tools_SURFSK_mesh.bl_category = context.user_preferences.addons[__name__].preferences.category
    bpy.utils.register_class(VIEW3D_PT_tools_SURFSK_mesh)
    VIEW3D_PT_tools_SURFSK_curve.bl_category = context.user_preferences.addons[__name__].preferences.category
    bpy.utils.register_class(VIEW3D_PT_tools_SURFSK_curve)

class BsurfPreferences(bpy.types.AddonPreferences):
    # this must match the addon name, use '__package__'
    # when defining this in a submodule of a python package.
    bl_idname = __name__

    category = bpy.props.StringProperty(
            name="Tab Category",
            description="Choose a name for the category of the panel",
            default="Tools",
            update=update_panel)

    def draw(self, context):

        layout = self.layout
        row = layout.row()
        col = row.column()
        col.label(text="Tab Category:")
        col.prop(self, "category", text="")


def register():
    bpy.utils.register_class(VIEW3D_PT_tools_SURFSK_mesh)
    bpy.utils.register_class(VIEW3D_PT_tools_SURFSK_curve)
    bpy.utils.register_class(GPENCIL_OT_SURFSK_add_surface)
    bpy.utils.register_class(GPENCIL_OT_SURFSK_edit_strokes)
    bpy.utils.register_class(CURVE_OT_SURFSK_reorder_splines)
    bpy.utils.register_class(CURVE_OT_SURFSK_first_points)
    bpy.utils.register_class(BsurfPreferences)


    bpy.types.Scene.SURFSK_cyclic_cross = bpy.props.BoolProperty(
        name="Cyclic Cross",
        description="Make cyclic the face-loops crossing the strokes",
        default=False)

    bpy.types.Scene.SURFSK_cyclic_follow = bpy.props.BoolProperty(
        name="Cyclic Follow",
        description="Make cyclic the face-loops following the strokes",
        default=False)

    bpy.types.Scene.SURFSK_keep_strokes = bpy.props.BoolProperty(
        name="Keep strokes",
        description="Keeps the sketched strokes or curves after adding the surface",
        default=False)

    bpy.types.Scene.SURFSK_automatic_join = bpy.props.BoolProperty(
        name="Automatic join",
        description="Join automatically vertices of either surfaces generated by crosshatching, or from the borders of closed shapes",
        default=True)

    bpy.types.Scene.SURFSK_loops_on_strokes = bpy.props.BoolProperty(
        name="Loops on strokes",
        description="Make the loops match the paths of the strokes",
        default=True)

    bpy.types.Scene.SURFSK_precision = bpy.props.IntProperty(
        name="Precision",
        description="Precision level of the surface calculation",
        default=2,
        min=1,
        max=100)


def unregister():
    bpy.utils.unregister_class(VIEW3D_PT_tools_SURFSK_mesh)
    bpy.utils.unregister_class(VIEW3D_PT_tools_SURFSK_curve)
    bpy.utils.unregister_class(GPENCIL_OT_SURFSK_add_surface)
    bpy.utils.unregister_class(GPENCIL_OT_SURFSK_edit_strokes)
    bpy.utils.unregister_class(CURVE_OT_SURFSK_reorder_splines)
    bpy.utils.unregister_class(CURVE_OT_SURFSK_first_points)
    bpy.utils.unregister_class(BsurfPreferences)

    del bpy.types.Scene.SURFSK_precision
    del bpy.types.Scene.SURFSK_keep_strokes
    del bpy.types.Scene.SURFSK_automatic_join
    del bpy.types.Scene.SURFSK_cyclic_cross
    del bpy.types.Scene.SURFSK_cyclic_follow
    del bpy.types.Scene.SURFSK_loops_on_strokes



if __name__ == "__main__":
    register()