Only triangulate n-gons when necessary for calc_tangents (godotengine…

…#379)

* Export from mesh.loop_triangles instead of mesh.polygons

This shouldn't change anything atm since the mesh is triangulated
beforehand, but this will allow us a non-triangulated mesh in the
future, which avoids problems where the mesh triangulation is wrong;
loop_triangles is always the "true" triangulation.

* Use mesh.loop_triangles for concave_shape

No longer need to ask the mesh converter to triangulate.

* Triangulate meshes if necessary for tangents

This means it is no longer required to ask for triangulation if
asking for tangents.

* Remove triangulate argument; now only triangulate for tangents

It is now as if it were always False. Triangulation will only
occur if needed for calc_tangents.

This was only True in mesh.py. Now that it is False there,
triangulate_mesh will be skipped for any meshes without (>4)-gons,
which solves issues of bad triangulation/damaged normals for these
meshes.

* Only triangulate n-gons when we can't calc_tangents

This should confine damage caused by triangulation to n-gons only.

* Warn when triangulating that exported n-gons may look wrong

* Test: make update-examples

io_scene_godot/converters/mesh.py

@@ -228,16 +228,17 @@ def export_morphs(self, export_settings, surfaces):
 
  surfaces_morph_data = self.intialize_surfaces_morph_data(surfaces)
 
- for face in shape_key_mesh.polygons:
+ shape_key_mesh.calc_loop_triangles()
+
+ for tri in shape_key_mesh.loop_triangles:
  surface_index = self.mesh_resource.get_surface_id(
- face.material_index
+ tri.material_index
  )
 
  surface = surfaces[surface_index]
  morph = surfaces_morph_data[surface_index]
 
- for loop_id in range(face.loop_total):
- loop_index = face.loop_start + loop_id
+ for loop_index in tri.loops:
  new_vert = Vertex.create_from_mesh_loop(
  shape_key_mesh,
  loop_index,
@@ -261,24 +262,24 @@ def generate_surfaces(self, escn_file, export_settings, mesh):
  """
  surfaces = []
 
- for face_index in range(len(mesh.polygons)):
- face = mesh.polygons[face_index]
+ mesh.calc_loop_triangles()
 
+ for tri in mesh.loop_triangles:
  # Find a surface that matches the material, otherwise create a new
  # surface for it
  surface_index = self.mesh_resource.get_surface_id(
- face.material_index
+ tri.material_index
  )
  if surface_index is None:
  surface_index = len(surfaces)
  self.mesh_resource.set_surface_id(
- face.material_index, surface_index
+ tri.material_index, surface_index
  )
  surface = Surface()
  surface.id = surface_index
  surfaces.append(surface)
  if mesh.materials:
- mat = mesh.materials[face.material_index]
+ mat = mesh.materials[tri.material_index]
  if (mat is not None and
  export_settings['material_mode'] != 'NONE'):
  surface.material = export_material(
@@ -291,9 +292,7 @@ def generate_surfaces(self, escn_file, export_settings, mesh):
  surface = surfaces[surface_index]
  vertex_indices = []
 
- for loop_id in range(face.loop_total):
- loop_index = face.loop_start + loop_id
-
+ for loop_index in tri.loops:
  new_vert = Vertex.create_from_mesh_loop(
  mesh,
  loop_index,
@@ -312,8 +311,7 @@ def generate_surfaces(self, escn_file, export_settings, mesh):
 
  vertex_indices.append(vertex_index)
 
- if len(vertex_indices) > 2: # Only triangles and above
- surface.vertex_data.indices.append(vertex_indices)
+ surface.vertex_data.indices.append(vertex_indices)
 
  if (export_settings['use_export_shape_key'] and
  has_shape_keys(self.object.data)):

io_scene_godot/converters/physics.py

@@ -148,7 +148,6 @@ def generate_convex_shape(escn_file, export_settings, bl_object):
  col_shape = None
  mesh_converter = MeshConverter(bl_object, export_settings)
  mesh = mesh_converter.to_mesh(
- triangulate=False,
  preserve_vertex_groups=False,
  calculate_tangents=False
  )
@@ -178,14 +177,14 @@ def generate_concave_shape(escn_file, export_settings, bl_object):
  col_shape = None
  mesh_converter = MeshConverter(bl_object, export_settings)
  mesh = mesh_converter.to_mesh(
- triangulate=True,
  preserve_vertex_groups=False,
  calculate_tangents=False
  )
  if mesh is not None and mesh.polygons:
  vert_array = list()
- for poly in mesh.polygons:
- for vert_id in reversed(poly.vertices):
+ mesh.calc_loop_triangles()
+ for tri in mesh.loop_triangles:
+ for vert_id in reversed(tri.vertices):
  vert_array.append(mesh.vertices[vert_id].co)
 
  col_shape = InternalResource("ConcavePolygonShape", mesh.name)

io_scene_godot/converters/utils.py

@@ -1,5 +1,6 @@
 """Util functions and structs shared by multiple resource converters"""
 
+import logging
 import bpy
 import bmesh
 
@@ -31,12 +32,12 @@ def restore_modifier_config(obj, modifier_config_cache):
  mod.show_viewport = modifier_config_cache[i]
 
 
-def triangulate_mesh(mesh):
- """Triangulate a mesh"""
+def triangulate_ngons(mesh):
+ """Triangulate n-gons in a mesh"""
  tri_mesh = bmesh.new()
  tri_mesh.from_mesh(mesh)
- bmesh.ops.triangulate(
-  tri_mesh, faces=tri_mesh.faces, quad_method="ALTERNATE")
+ ngons = [face for face in tri_mesh.faces if len(face.verts) > 4]
+ bmesh.ops.triangulate(tri_mesh, faces=ngons, quad_method="ALTERNATE")
  tri_mesh.to_mesh(mesh)
  tri_mesh.free()
  if bpy.app.version[1] > 80:
@@ -117,7 +118,7 @@ def __init__(self, obj, export_settings):
  self.use_export_shape_key = export_settings['use_export_shape_key']
  self.has_tangents = False
 
- def to_mesh(self, triangulate=True, preserve_vertex_groups=True,
+ def to_mesh(self, preserve_vertex_groups=True,
  calculate_tangents=True, shape_key_index=0):
  """Evaluates object & converts to final mesh, ready for export.
  The mesh is only temporary, call to_mesh_clear() afterwards."""
@@ -152,13 +153,19 @@ def to_mesh(self, triangulate=True, preserve_vertex_groups=True,
  # mesh result can be none if the source geometry has no faces, so we
  # need to consider this if we want a robust exporter.
  if mesh is not None:
- if triangulate:
- triangulate_mesh(mesh)
-
  self.has_tangents = bool(mesh.uv_layers) and bool(mesh.polygons)
  if calculate_tangents:
  if self.has_tangents:
- mesh.calc_tangents()
+ try:
+ mesh.calc_tangents()
+ except RuntimeError:
+ # Mesh must have n-gons
+ logging.warning(
+ "Mesh had n-gons and had to be triangulated to "
+ "calculate tangents; n-gons may look wrong."
+ )
+ triangulate_ngons(mesh)
+ mesh.calc_tangents()
  else:
  mesh.calc_normals_split()