CN109558665B - Automatic design method of personalized flexible nose pad - Google Patents
Automatic design method of personalized flexible nose pad Download PDFInfo
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Abstract
The invention discloses an automatic design method of a personalized flexible nose pad, which comprises the following steps: (1) Obtaining a model of a nose region in a human face to obtain a point cloud set of the region; (2) Selecting a standard bracket model of a flexible nose support, and dividing the model into a rigid nose support part, a nose support surface part, a deformable part and a base part; (3) Sampling the surface of the supporting blade, and mapping a sampling point to a local coordinate system established by the surface part of the nose bracket; (4) selecting a spectacle frame model, and initializing a bracket position; (5) According to the nose area point cloud set, the bracket position and the mapping relation, moving the leaf supporting sampling point to the nose surface closest to the point by using an iterative zooming method, and updating a bracket grid; and after the iteration is finished, combining the bracket standard model and the spectacle frame standard model to finish the design of the flexible nose pad. The flexible nose support is automatically optimized according to the shape of the nose of a user, has high fitting degree with the nose, and adapts to the asymmetry of the face.
Description
Technical Field
The invention belongs to the technical field of design and manufacture of glasses, and particularly relates to an automatic design method of a personalized flexible nose pad based on three-dimensional measurement of a human face.
Background
The nose pad is a part of the spectacle frame which plays a supporting role on the nose bridge, and has very important influence on the wearing comfort and the aesthetic property of the spectacles. The adjustable nose pad is divided from adjustable degree, and the design modes of the nose pad of the existing glasses can be divided into three types, namely fixed general design, adjustable design and personalized customization design.
The fixed general design is mainly used for non-metal spectacle frames, the design is to determine a set of fixed shapes and parameters, namely a 'model', according to typical nose bridge data of a target group, the fixed general nose pad design cannot provide the possibility of adjustment, and a user needs to select one from a plurality of models to wear the glasses comfortably.
The adjustable design can be further divided into a blade-supporting movable type and a mechanism adjusting type. The nose pad with movable supporting blades is mainly applied to a metal frame, and the nose pad is composed of two parts, namely a supporting blade and a supporting arm. The blade supporting part consists of a blade and a supporting pile, and the supporting pile is embedded in the blade by a base plate and fixed in the blade. The support arm is also composed of two parts, one is a support stem and the other is a pile box, the support stem is a connecting part of the spectacle frame body (a lens ring or a beam) and the pile box, and the pile box is a part for accommodating the support pile. The supporting blade and the supporting arm form a whole by means of a screw, and the whole has a certain adjusting space, including the height of the nose support, the angle of the blade, the relative position of the blade and the spectacle frame and the like. The supporting blade can be naturally adjusted within a certain angle (usually 20 to 40 degrees from the left to the right and 10 to 30 degrees from the top to the bottom) by taking the fixing screw as a shaft. The nose pad with movable supporting blades is usually required to be properly adjusted in structure by a staff member in an eyeglass shop by means of a professional tool when the eyeglasses are delivered, and the natural adjustment capability of the supporting blades is relied on to adapt to the nose shapes of different users. In order to solve the problem, an adjustable nose pad (see a convenient adjustable glasses nose pad disclosed by the utility model with the publication number of CN207586567U, glasses with an adjustable nose pad disclosed by the utility model with the publication number of CN207833134U, height-adjustable glasses with a nose pad disclosed by the utility model with the publication number of CN207924283U, and a 360-degree bilateral adjustable Ergonose XI nose pad released by Rudy Project in 2017 of sports glasses manufacturer) is provided, and the basic idea is to utilize mechanical structures such as gears and threaded rods to adjust the height, orientation and other parameters of the nose pad. The problem with this type of design is that manual adjustment is still required, although the process of adjustment may not require special tools. The nose pad is more complicated to manufacture and more expensive than the above movable nose pad due to the mechanical structure for adjustment.
With the commercialization of three-dimensional scanning technology, it becomes easy and popular to obtain a three-dimensional model of the face of a user, and on this basis, people have proposed a personalized custom made spectacle frame and nose pad based on three-dimensional measurement of the face (see the spectacle frame design method based on three-dimensional measurement of the face disclosed in the invention patent with publication number CN 105842875A). The final generated spectacle frame model is produced by means of 3D printing. The problem with this kind of personalized custom design based on 3D printing is that because the mirror holder model can not pass through the mould at last and need to print with 3D just can accomplish the production with acceptable cost, the 3D printing material that is used for the mirror holder needs certain hardness, and the 3D printing technique of present mixed material is still not mature, therefore the nose holds up the hard material like the mirror holder, and this makes and wears the travelling comfort and has influenced. Traditional glasses have the scheme that improves the wearing comfort through the silica gel pad, however the thickness of silica gel pad can influence the laminating degree of nose support, and because the shape of individualized customization nose support is unfixed, this has also brought very big difficulty for the design of silica gel pad.
In the aspect of the design and the manufacture of the nose pad, a new technology which has the advantages of good fitting degree, soft material, simple manufacture and low cost and can ensure the wearing comfort is needed at present.
Disclosure of Invention
In view of the above problems, an object of the present invention is to provide an automatic design method for a personalized flexible nose pad, which can automatically generate a flexible nose pad that fits the face of a user according to an existing three-dimensional face model of the user and a corresponding standard piece of a spectacle frame.
An automatic design method of a personalized flexible nose pad comprises the following steps:
(1) Acquiring a nose region part model in a human face and a point cloud set of the region;
(2) Selecting a standard bracket model of the flexible nose pad, and dividing the model into: a rigid nose bracket part for embedding the support blade, a nose support surface part jointed with the support blade, a deformable part and a base part fixed with the spectacle frame;
(3) Sampling the surface of a blade to be embedded into the bracket, and mapping the obtained blade sampling point to a local coordinate system established by the surface part of the nose pad seat;
(4) Selecting a standard model or a customized model of the spectacle frame, initializing the position of a bracket, and fitting the base part of the bracket with a preset position on the spectacle frame;
(5) According to the nose area point cloud set obtained in the step (1) and the bracket position in the step (4), successively moving a leaf supporting sampling point to the nose surface closest to the point by using an iterative zooming method, calculating the position of the surface part of the nose support according to the mapping relation, and updating the bracket grid; after the iteration is finished, combining the bracket standard model and the spectacle frame standard model to obtain a synthesized complete spectacle frame network, and finishing the design of the flexible nose pad;
optionally, the 3D printing method is selected for the flexible nose pad, including the manufacturing of the spectacle frame.
The step (1) specifically comprises the following steps:
(1-1) obtaining a three-dimensional grid model and a three-dimensional face characteristic point set of a face region by using a three-dimensional measurement method;
(1-2) reading two nose side points and the position of a nose bridge point in a three-dimensional grid model of the face region;
and (1-3) according to the rectangle formed by the four points, digging out a corresponding position in the three-dimensional grid model as a nose area part model, wherein the part is a joint position of the supporting leaf.
In the step (1-1), the three-dimensional measurement of the human face can be realized by adopting a plurality of modes, and preferably, the three-dimensional grid model of the human face area can be obtained by one or a combination of a plurality of methods:
1) A stereoscopic vision imaging method using a binocular or multi-view camera;
2) A structured light based three-dimensional scanning method;
3) A three-dimensional laser scanning method based on triangular ranging;
4) A three-dimensional scanning method based on time-of-flight ranging.
In the step (2), the model parameters include positions of the following regions in a set bracket coordinate system, specifically: the nose support comprises a base area, a nose support seat area, a hollow nose support seat area and a nose support seat surface area, wherein the base area is formed by intersecting the bracket and the spectacle frame; these parameters are given by the designer of the nose bracket, in the form of a bounding box.
Generally, the regions in step (2) will not be standard cuboids or rectangles, and in order to reduce the marking cost of the design side, the regions are represented by cuboids or rectangles. The designer of the bracket standard model needs to give the top point of a cuboid or a rectangle, wherein the base area where the bracket and the picture frame are intersected is a rectangle controlled by 4 top points, the nose support seat area for embedding the support blade part is a cuboid controlled by 8 top points, the hollow area of the nose support seat is a cuboid controlled by 8 top points, and the surface area of the nose support seat attached to the support blade is a rectangle controlled by 4 top points.
Preferably, the bracket coordinate system takes a point where the center axis of the nose support seat intersects with the surface of the nose support seat as a coordinate origin, the longer direction of the nose support seat is a Y axis, the short direction of the nose support seat is an X axis, and the Z axis is set so that Z coordinates of all points of the bracket model are positive. The bounding box given in such a coordinate system is mostly aligned with the axis, effectively improving the accuracy and robustness of the next step.
The step (2) specifically comprises the following steps:
(2-1) obtaining a rigid nose bracket part of the standard bracket model;
in the automatic design process, in order to ensure that the nose bracket used for embedding the supporting blade in the standard model does not deform excessively, the part needs to be set as a rigid body.
And calculating points in the bounding box according to the bounding box corresponding to the read corresponding region, and recording subscripts of the points in the standard model data to be marked as a rigid body part of the standard model.
(2-2) obtaining the surface part of the nose pad seat;
since the blades are actually fitted to the nose, in order to reduce the scale of calculation, it is not necessary to take the model of the blades into account, but to indirectly calculate the model through the portion of the nose pad surface fitted with the blades.
Points within the bounding box are found from the read surface region bounding box, and the subscripts of these points are recorded as the surface portion of the standard model.
(2-3) in the automatic design process, in order to ensure the proper position of the mounting on the frame, the subscripts of these points are found from the read intersection area bounding box, and are denoted as fixed points.
(2-4) the remaining part is a nose pad deformable part.
Since the floating point number is expressed with an error in the computer, preferably, in order to determine the point contained in the corresponding bounding box in step (2), the bounding box needs to be slightly enlarged by a small Delta distance, so that the points located on the bounding box can be recorded smoothly.
The specific steps of the step (3) are as follows:
(3-1) uniformly sampling a plurality of points along the surface of the blade to form a sampling point set, and linearly mapping the sampling point set to partial points on the surface of the nose pad;
(3-2) selecting three points on the surface part of the nose support seat of the standard bracket model by using a farthest point sampling method, and establishing a local coordinate system; the local coordinate system is established as follows:
and taking the first point as the origin of a coordinate system, taking the unitized vector of the difference between the second point and the origin as an x-axis, cross-multiplying the difference between the third point and the origin with the x-axis to obtain a z-axis, and cross-multiplying the z-axis with the x-axis to obtain a y-axis, thus defining a local coordinate system (3-3) established by the points of the surface part, calculating the difference vectors of the sampling points and the points mapped to the surface part of the nose bracket under a world coordinate system, and expressing the calculated difference vectors by using the local coordinate system.
Thus, after the whole bracket is moved, the sampling points of the leaf supporting can be recalculated through the three sampled points and the difference vector of the local coordinate system.
In the step (4), the spectacle frame model may be a standard model in a model library, or a model customized in advance according to the human face characteristics and the preference of the user, and the customized model may be generated automatically or manually.
The steps of initializing the carriage position are as follows:
(4-1) calculating the center of the upper base of the bracket, calculating a conversion matrix from the center to a preset position on the glasses frame, and moving the whole bracket by using the conversion matrix so that the center of the upper base coincides with the preset position;
(4-2) calculating a normal vector of the upper base and a normal vector of the preset position, and calculating a rotation matrix to enable the normal vector of the upper base to be opposite to the normal vector of the preset position after rotation, and after the bracket is rotated by utilizing the matrix, the upper base is attached to the preset position;
(4-3) calculating the trend unit vectors of the center of the upper base and the center of the lower base, calculating the trend unit vectors of the corresponding positions of the spectacle frame, calculating a rotation matrix, enabling the trend of the base to be the same as the trend of the spectacle frame after rotation, and utilizing the matrix to rotate the bracket, and then attaching the lower base to the spectacle frame.
The step (5) specifically comprises the following steps:
(5-1) calculating the world coordinates of the sampling point set after the bracket position is initialized according to the difference vector of the local coordinate system in the step (3);
(5-2) finding a point which is closest to the nose region part in the step (1) for each point in the sampling point set, and calculating a point set corresponding to the surface point when the sampling point is coincident with the closest point according to a difference vector of a local coordinate system, and marking the point set as a constraint point set;
(5-3) moving the surface points to the constraint points in a successive segmentation manner by an iteration method, updating the bracket network, and recalculating the constraint point set after each movement;
and (5-4) when iteration converges or reaches a preset iteration number, combining the bracket standard model and the spectacle frame standard model to obtain a synthesized complete spectacle frame network.
In the step (5-3), when the bracket network is updated, the Laplacian distortion method is adopted to solve the vertex position of each part on the bracket, and in order to ensure that the nose support seat part does not change in a non-rigid body during iteration, optimization of the position constraint and the rigid body constraint is solved at the same time by setting a Laplacian weight with a larger rigid body nose support seat part point.
According to the difference between the iteration times and the convergence situation, the actual constraint points adopted in the Laplacian Deformation method are preprocessed. When iteration starts, the actual constraint points are points of the solved constraint points which are wholly moved for a certain distance along respective normal directions, the closer the actual constraint points are to the solved constraint points along with the increase of iteration times, and the actual constraint points are the solved constraint points during later-stage iteration. The method is used for preventing the phenomenon that the quality of the grid of the solving bracket is poor due to the fact that the moving distance of some points is too large in the Laplacian Deformation process.
After the entire frame is designed, the entire frame can be fabricated using conventional methods, such as three-dimensional printing techniques, including selective laser sintering techniques or stereolithography techniques.
After the picture frame is printed, the support piles of the standard parts of the support blades are embedded into the hollow areas on the nose support seat, and the blades of the support blades are just attached to the surface areas of the nose support seat. The method ensures that the nose pad seat can not deform while the pad leaf can be attached to the nose.
Compared with the prior art, the invention has the beneficial effects that:
1. the flexible nose support is automatically optimized according to the shape of the nose of a user, has high fitting degree with the nose, and adapts to the asymmetry of the face;
2. the nose pad is almost automatically generated, and a user can operate the nose pad only by roughly knowing the meaning of each parameter;
3. the invention has simple manufacture and low cost, and greatly shortens the manufacturing time.
Drawings
FIG. 1 is a flow chart of an automated design method for a personalized flexible nose pad according to the present invention;
FIG. 2 is a schematic diagram of the present invention using feature points to find nose region points in a three-dimensional face model;
FIG. 3 shows a pallet model and a given bounding box under a canonical coordinate system: (a) is a top view of the bracket; (b) is a perspective view; (c) is a bottom view; (d) is a side view;
fig. 4 shows the sampling results of the leaf: (a) sampling along the long axis direction of the nose pad seat; (b) sampling along the short axis direction of the nose pad;
fig. 5 illustrates the process of initializing the carriage position: (a) is a schematic diagram of the position of the preliminary moving nose bracket; (b) is a schematic view of the position of the nose bracket for the first rotation; (c) the position of the nose bracket is schematically shown in the second rotation;
FIG. 6 illustrates an iterative nose pad closeout process; (a) positions of sampling points of an iteration forenose bracket and a supporting blade; (b) is a comparison graph of 5 iterations and before iteration; (c) comparing the iteration completion with the iteration;
FIG. 7 is a schematic view of the resulting frame at various angles;
fig. 8 is a real shot of the finished glasses at different angles.
Detailed Description
The invention will be described in further detail below with reference to the drawings and examples, which are intended to facilitate the understanding of the invention and are not intended to limit it in any way.
As shown in fig. 1, an automatic design method for a personalized flexible nose pad includes the steps of reading a nose model 101, reading a nose pad model and parameters 102, sampling pad leaves 103, initializing a nose pad position 104, iteratively drawing a nose pad 105, and the like, and details of implementation of each step are described in detail below.
1. Reading a nose model, referring to fig. 2:
and (1-1) reading a face model of the target object and a corresponding characteristic point set calculated by adopting other methods.
(1-2) find a smallest rectangle from the front view, which includes exactly point 106, point 107, point 108, and point 109.
(1-3) model in a front view, a point within a rectangle is a definition field of a nose model used in the present invention, that is, a region to which a leaf support should be attached.
2. Reading the nose pad model and parameters, with reference to fig. 3:
after the nose pad design designer finishes designing the nose pad, parameters of the nose pad model need to be given for the automatic design method of the present invention to use. The designer sets a coordinate system for the nose pad firstly, the intersection point of the center axis of the nose pad seat and the surface of the nose pad seat is used as a coordinate origin, the longer direction of the nose pad seat is a Y axis, the short direction of the nose pad seat is an X axis, and the Z axis is set to enable the Z coordinates of all points of the bracket model to be positive.
The coordinate system lower bracket model and the given bounding box are shown in fig. 3 (a), (b), (c), and (d), and are all calibrated on the coordinate axis in the positive direction. The rigid body portion of the bracket is designated by an axisymmetric bounding box, the nosepiece portion of the drawing; the hollow part is used for calculating the mapping relation of the sampling points and is also specified by an axisymmetric bounding box; the surface part is a point with the Z coordinate of the nose bracket equal to 0 and is specified by the bottom surface of the enclosing box of the rigid body part; the fixed part is the base area indicated in the figure and is designated by a rectangle; the remaining portion is a deformable portion.
Because the bounding box is axisymmetric, the points in the bounding box can be determined only by whether the three-dimensional coordinates of the check points are in the interval. The determination of the area specified by the rectangle is by determining whether the point is on the face of the rectangle.
3. Leaf surface sampling, see fig. 4:
in fig. 4, (a) shows the sampling points are uniformly sampled along the major axis, and (b) shows the sampling points are uniformly sampled along the minor axis. In the figure, the long axis samples 10 segments and the short axis samples 8 segments, i.e. 99 points in total. And (3) performing linear mapping on the sampling points to form 99 sampling point sets { sample _ pos _ i } and surface point lower standard sets { surface _ idx _ i } combined point pairs, and calculating a difference vector set { Vec _ wi } of the point pairs.
The method comprises the steps of selecting three points coord1, coord2 and coord3 on the surface portion of a nose bracket model by adopting a farthest point sampling method, recording subscripts of the three points coord1, coord2 and coord3, taking a first point as an origin of a coordinate system, taking a unitized vector of a difference between a second point and the origin as an x axis, multiplying a difference between a third point and the origin by the x axis to obtain a z axis, and finally multiplying the z axis by the x axis to obtain a y axis, so that a local coordinate system established by the points of the surface portion is defined. The x, y and z axes are used as column vectors to form a matrix M _ r.
For the difference vector set { Vec _ wi }, left-multiplying Vec _ wi by the transpose of the matrix M _ r to obtain a difference vector set { Vec _ oi = (M _ r) in the local coordinate system T * Vec _ wi }. The set of difference vectors can be used to recalculate the position of the blade sampling point after the nose pad is moved.
4. Initializing nose pad position, see fig. 5:
fig. 5 (a) is a schematic diagram of the position of the preliminary mobile nose bracket, and the specific method is as follows: calculating the center of one of the bases of fig. 3, in which the base to be finally fitted to the upper part of the frame is used; then, according to the position of the spectacle frame appointed by the user, the whole nose bracket is moved, so that the center of the base is coincided with the appointed position.
Fig. 5 (b) is a schematic view of the position of the first rotation of the nose bracket, and it can be seen that after the rotation, the upper base and the frame are already attached, the specific method is as follows: calculating a normal vector of the base which is superposed with the position of the spectacle frame, and simultaneously calculating a normal vector of the corresponding position of the spectacle frame; the entire nose bracket is then rotated about the center of the base such that the two normal vectors are exactly opposite.
Fig. 5 (c) is a schematic diagram of the position of the nose bracket rotated for the second time, and it can be seen that after the rotation, the initial position of the whole nose bracket is correct, and the specific method is as follows: according to the distance D between the center of the lower base and the center of the upper base, a point P is obtained on the mirror frame, and the distance between the point P and the center of the upper base is also D; then the whole nose bracket is rotated around the center of the upper base, so that the center of the lower base is coincided with the point P on the glasses frame.
5. Iterative approach to nose pads, see fig. 6:
(5-1) recalculating the sampling point set { sample _ pos _ i } according to the surface point set { surface _ idx _ i } in the step 3, the local coordinate system points coord1, coord2 and coord3 and the difference vector set { Vec _ oi } in the local coordinate system, wherein in (a), the positions of the sampling points of the leaf are determined after the bracket positions are initialized;
(5-2) in the nose area points found in the step 1, for each point in the sampling point set { sample _ pos _ i }, finding a closest point set { target _ pos _ i }, and then calculating a constraint point set { constraint _ pos _ i } through a surface point set { surface _ idx _ i }, local coordinate system points coord1, coord2 and coord3, and a difference vector set { Vec _ oi } in a local coordinate system, wherein the meaning of the point set is that after the surface point moves to the constraint point, the sampling point coincides with the closest point.
And (5-3) moving the surface points to the constraint points by successive segmentation through an iterative method, and updating the bracket grid. After each move, the set of constraint points is recalculated. A comparison of the 5 initialization and iteration is shown in fig. 6 (b). A comparison of the initialisation and iteration is shown in figure 6 (c), and it can be seen that the sampling point has been substantially fully fitted to the nose after the iteration has been completed.
(5-4) with the constraint point set as a constraint, adopting a Laplacian Deformations method (see a course in https:// www. Cse. Wustl. Edu/. Taoju/cse554/lectures/lect08_ Deformations. Pdf or a document Cohenor D. Laplacian surface evaluation [ C ]// Eurographics/acm graph Symposium on Geometry processing. ACM, 2004.) to establish a Laplacian constraint model and solve the positions of other vertexes on the bracket by solving a linear equation set. In the solving process, in order to ensure that the nose support seat part does not change the non-rigid body during iteration, the Laplacian weight of the nose support, namely the rigid body part point, is set to be larger than that of other points, and through Laplacian Deformation performed by the method, the rigid body property of the nose support is protected in the process, so that the optimization problem with position constraint and rigid body constraint can be solved simultaneously.
(5-5) according to the difference between the iteration times and the convergence situation, preprocessing the adopted actual constraint points in the Laplacian reconstruction method. In the first half of iteration, the actual constraint points are the points after the whole solved constraint points move a certain distance along the respective normal directions, the distance is reduced along with the increase of the number of iterations, and the actual constraint points are the solved constraint points during the iteration of the later section. The method can prevent the moving distance of points in the Laplacian Deformation process from being overlarge, thereby not only avoiding the situation of solving the problem that the quality of the grid of the bracket is poor, but also being beneficial to solving a more correct constraint point set.
And (5-6) after the iteration is finished, combining the bracket model with the mirror frame model to obtain a result mirror frame. Fig. 7 (a), (b), and (c) are schematic diagrams of the finally synthesized mirror frame at three angles, and black dots are positions of sampling points after iteration, and it can be seen that both the left and right blades are attached to the nose.
6. Three-dimensional printing
The physical spectacle frame is formed by using a three-dimensional printing technology, such as Selective Laser Sintering (SLS, see the term "Selective Laser Sintering" in encyclopedia) technology or stereolithography (SLA, see the term "stereolithography" in encyclopedia) technology, and the like, according to the three-dimensional mesh model of the spectacle frame generated in the foregoing steps.
After the picture frame is printed, the support piles of the standard parts of the support blades are embedded into the hollow areas on the nose support seat, and the blades of the support blades are just attached to the surface areas of the nose support seat.
With the method of the present invention, the resulting frame is designed to be printed using SLA, and fitted with standard parts of the blades and lenses, and after post-processing, the effect is shown in fig. 8 (a), (b) and (c). The three-dimensional measurement object can achieve very good fitting degree by wearing the spectacle frame, and is not easy to slide after wearing. The nose of the subject is left-right asymmetric, and the resulting frame can adapt well to this asymmetry, fitting its nose completely.
The embodiments described above are intended to illustrate the technical solutions and advantages of the present invention, and it should be understood that the above-mentioned embodiments are only specific embodiments of the present invention, and are not intended to limit the present invention, and any modifications, additions and equivalents made within the scope of the principles of the present invention should be included in the scope of the present invention.
Claims (8)
1. An automatic design method of a personalized flexible nose pad is characterized by comprising the following steps:
(1) Acquiring a nose region part model in a human face and a point cloud set of the region;
(2) Selecting a standard bracket model of the flexible nose pad, and dividing the model into: a rigid nose bracket part for embedding the support blade, a nose support surface part jointed with the support blade, a deformable part and a base part fixed with the spectacle frame;
(3) Sampling the surface of a supporting blade to be embedded into the bracket, and mapping the obtained supporting blade sampling point to a local coordinate system established by the surface part of the nose bracket; the method comprises the following specific steps:
(3-1) uniformly sampling a plurality of points along the surface of the blade support to form a sampling point set, and linearly mapping the sampling point set to partial points on the surface of the nose support seat;
(3-2) selecting three points on the surface part of the nose support seat of the standard bracket model by using a farthest point sampling method, and establishing a local coordinate system;
(3-3) calculating difference vectors of the sampling points and the points mapped to the surface part of the nose bracket under a world coordinate system, and expressing the calculated difference vectors by using a local coordinate system;
(4) Selecting a standard model or a customized model of the spectacle frame, initializing the position of a bracket, and fitting the base part of the bracket with a preset position on the spectacle frame;
(5) According to the nose area point cloud set obtained in the step (1) and the bracket position in the step (4), successively moving the leaf supporting sampling point to the nose surface closest to the point by using an iterative zooming method, calculating the position of the surface part of the nose support according to the mapping relation, and updating a bracket network; after iteration is completed, combining the bracket standard model and the spectacle frame standard model to obtain a synthesized complete spectacle frame network, and completing the design of the flexible nose pad;
the 3D printing method is selected to carry out the flexible nose pad, including the manufacturing of the spectacle frame.
2. The automatic design method of the personalized flexible nose pad according to claim 1, wherein the step (1) specifically comprises:
(1-1) obtaining a three-dimensional grid model and a three-dimensional facial feature point set of a human face region by using a three-dimensional measurement method;
(1-2) reading two nose side points and the position of a nose bridge point in a three-dimensional grid model of the face region;
and (1-3) according to the rectangle formed by the four points, picking out the corresponding position in the three-dimensional grid model as a nose region part model.
3. The method for automatically designing an individualized flexible nose pad according to claim 1, wherein in the step (2), the model parameters include positions of the following regions in a set bracket coordinate system, specifically: the nose support comprises a base area, a nose support seat area, a hollow area and a nose support seat surface area, wherein the base area is intersected with the glasses frame by a bracket; these parameters are given by the designer of the nose cradle, in the form of a bounding box.
4. The automatic design method of the personalized flexible nose pad according to claim 3, wherein the bracket coordinate system takes the point where the center axis of the nose pad intersects with the surface of the nose pad as the origin of coordinates, the longer direction of the nose pad is the Y axis, the shorter direction is the X axis, and the Z axis is set so that the Z coordinates of all points of the bracket model are positive.
5. The automated design method of the personalized flexible nose pad according to claim 1, wherein in the step (4), the step of initializing the position of the cradle is as follows:
(4-1) calculating the center of the upper base of the carrier, calculating a transformation matrix from the center to a preset position on the glasses frame, and moving the entire carrier using the transformation matrix such that the center of the upper base coincides with the preset position;
(4-2) calculating a normal vector of the upper base and a normal vector of the preset position, and calculating a rotation matrix to enable the normal vector of the upper base to be opposite to the normal vector of the preset position after rotation, and after the bracket is rotated by utilizing the matrix, the upper base is attached to the preset position;
(4-3) calculating the direction unit vectors of the center of the upper base and the center of the lower base, calculating the direction unit vectors of the corresponding positions of the spectacle frame, calculating a rotation matrix, enabling the direction of the base to be the same as the direction of the spectacle frame after rotation, and enabling the lower base to be attached to the spectacle frame after the bracket is rotated by utilizing the matrix.
6. The automatic design method of the personalized flexible nose pad according to claim 1, wherein the step (5) specifically comprises:
(5-1) calculating the world coordinates of the sampling point set after the bracket position is initialized according to the difference vector of the local coordinate system in the step (3);
(5-2) finding a point closest to the nose region part in the step (1) for each point in the sampling point set, and calculating a point set corresponding to the surface point when the sampling point is coincident with the closest point according to a difference vector of a local coordinate system and recording the point set as a constraint point set;
(5-3) moving the surface points to the constraint points in a successive segmentation manner by an iteration method, updating the bracket network, and solving the constraint point set again after moving each time;
and (5-4) when iteration converges or reaches a preset iteration number, combining the bracket standard model and the spectacle frame standard model to obtain a synthesized complete spectacle frame network.
7. The automated design method for the personalized flexible nose pad according to claim 6, wherein in the step (5-3), when updating the cradle network, the Laplacian reconstruction method is adopted to solve the vertex positions of the parts on the cradle, and when solving, relatively large Laplacian weights are set for the rigid nose pad part points.
8. The automatic design method of the personalized flexible nose pad as claimed in claim 6, wherein at the beginning of the iteration, the actual constraint points are the points at which the solved constraint points are wholly moved a certain distance along their respective normal directions, and as the number of iterations increases, the closer the actual constraint points are to the solved constraint points, and at the later stage of the iteration, the actual constraint points are the solved constraint points.
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| CN111467131B (en) * | 2020-04-30 | 2022-05-27 | 浙江大学 | Automatic design method for 3D printing customized goggles frame |
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