Three-dimensional model generation method and device, electronic equipment and product

Abstract

The invention provides a three-dimensional model generation method and device, electronic equipment and a product, and the method comprises the steps: carrying out the folding simulation based on a two-dimensional graph and a folding reference of the two-dimensional graph, and obtaining a folded three-dimensional open structure; wherein the folding reference comprises a folding angle and a folding mark; the closing type for closing the three-dimensional open structure is determined, and the closing type comprises any one of polygon closing, curved surface closing and polygon and curved surface mixed closing; and based on the closing type of the three-dimensional open structure, performing closing processing on the three-dimensional development structure to obtain a three-dimensional model after the two-dimensional graph is folded according to the folding reference. According to the technical scheme, the open structure which is not closed after being turned over can be automatically closed, the closed three-dimensional model obtained after the two-dimensional graph is turned over according to the turning reference is obtained, the visualization effect of the three-dimensional structure obtained after the two-dimensional graph is turned over is improved, and the experience degree of a user for observing the turning effect is improved.

Description

Technical Field

[0001] This application relates to the field of 3D modeling technology, and in particular to a method, apparatus, electronic device and product for generating 3D models. Background Technology

[0002] In fields such as computer graphics, industrial design, and mathematics education, converting two-dimensional designs into three-dimensional models is a fundamental and crucial requirement. Especially in STEM education, maker education, and paper art design, users often need to use intuitive folding operations to transform two-dimensional unfolded diagrams into three-dimensional structures to verify design feasibility, assist in teaching demonstrations, or create works of art.

[0003] However, when two-dimensional graphics are folded along creases, they typically form open, unclosed structures rather than complete solids. The visualization of these open, unclosed structures is poor, affecting the user's observation of the folding effect. Therefore, how to transform the open structures formed by folding two-dimensional graphics into closed, three-dimensional structures to improve visualization is a pressing technical problem that needs to be solved in this field. Summary of the Invention

[0004] Based on the above requirements, this application proposes a method, apparatus, electronic device and product for generating three-dimensional models, which can transform an open structure formed by folding a two-dimensional graphic into a closed three-dimensional structure, thereby improving the visualization effect of the three-dimensional structure.

[0005] To achieve the above objectives, this application proposes the following technical solution: According to a first aspect of the embodiments of this application, a method for generating a three-dimensional model is provided, comprising: Based on the two-dimensional graphic and the folding reference of the two-dimensional graphic, a folding simulation is performed to obtain the three-dimensional open structure after folding; wherein, the folding reference includes the folding angle and the crease; Determine the closure type for closing the three-dimensional open structure, wherein the closure type includes any one of polygonal closure, surface closure, and hybrid closure of polygons and surfaces; Based on the closure type of the three-dimensional open structure, the three-dimensional open structure is closed to obtain a three-dimensional solid model after the two-dimensional graphic is folded according to the folding reference.

[0006] Optionally, determine the type of closure to be applied to the three-dimensional open structure, including: Feature extraction is performed on the three-dimensional open structure to obtain structural features, and based on the structural features, the geometric properties of the open boundary of the three-dimensional open structure are determined; wherein, the geometric properties include: polygonal edges or curved edges; If the geometric properties of all open boundaries of the three-dimensional open structure are polygonal edges, then the closure type corresponding to the three-dimensional open structure is determined to be polygonal closure. If the geometric properties of all open boundaries of the three-dimensional open structure are curved edges, then the closure type corresponding to the three-dimensional open structure is determined to be surface closure. If the three-dimensional open structure includes open boundaries with polygonal edges as geometric attributes and open boundaries with curved edges as geometric attributes, then the closure type corresponding to the three-dimensional open structure is determined to be a hybrid closure of polygons and surfaces.

[0007] Optionally, based on the closure type of the three-dimensional open structure, the three-dimensional open structure is closed to obtain a three-dimensional solid model of the two-dimensional graphic after being folded according to the folding reference, including: If the closure type of the three-dimensional open structure is polygonal closure, then a coordinate system is constructed for the three-dimensional open structure, and a set of flipped vertices and a set of fixed vertices are obtained; wherein, the set of flipped vertices contains the vertices of the flipped surfaces in the three-dimensional open structure, and the set of fixed vertices contains the vertices of the fixed surfaces in the three-dimensional open structure; Based on the coordinate system, the flipped vertex set, and the fixed vertex set, determine the vertex correspondence between the flipped vertex set and the fixed vertex set; Based on the vertex correspondence, the closed surface of the three-dimensional open structure is constructed to obtain the three-dimensional solid model after the two-dimensional graphic is folded according to the folding reference.

[0008] Optionally, based on the coordinate system, the flipped vertex set, and the fixed vertex set, the vertex correspondence between the flipped vertex set and the fixed vertex set is determined; Based on the coordinate system, the vertices in the flipped vertex set are sorted, and the vertices in the fixed vertex set are sorted. If the number of vertices in the flipped vertex set and the fixed vertex set are different, then the vertices in the flipped vertex set and the vertices in the fixed vertex set are matched in order from the edge to the inside to obtain the initial matching relationship and the remaining vertices without matching relationship; According to the vertex order of the flipped vertex set and the fixed vertex set, determine the vertices corresponding to the remaining vertices to obtain the correspondence of the remaining vertices; The initial correspondence and the remaining vertex correspondence are combined to obtain the vertex correspondence between the flipped vertex set and the fixed vertex set; If the number of vertices in the flipped vertex set and the fixed vertex set are the same, then a one-to-one correspondence is established between the vertices in the flipped vertex set and the vertices in the fixed vertex set to obtain the vertex correspondence relationship between the flipped vertex set and the fixed vertex set.

[0009] Optionally, based on the closure type of the three-dimensional open structure, the three-dimensional open structure is closed to obtain a three-dimensional solid model of the two-dimensional graphic after being folded according to the folding reference, including: If the closure type of the three-dimensional open structure is curved surface closure, then obtain the first arc of the folded surface in the three-dimensional open structure and the second arc of the fixed surface in the three-dimensional open structure; Based on the first arc and the second arc, determine the connection curve between the first arc and the second arc; Based on the connection curve between the first arc and the second arc, the closed surface of the three-dimensional open structure is constructed to obtain the three-dimensional solid model of the two-dimensional graphic after being folded according to the folding reference.

[0010] Optionally, based on the first arc and the second arc, a connection curve between the first arc and the second arc is determined, including: According to the point extraction ratio, select the first arc point in the first arc and the second arc point in the second arc, and make a one-to-one correspondence between the first arc point and the second arc point to obtain the point correspondence relationship; Based on the point correspondence, a cycloid is constructed between the corresponding points to obtain the connection curve between the first arc and the second arc.

[0011] Optionally, based on the closure type of the three-dimensional open structure, the three-dimensional open structure is closed to obtain a three-dimensional solid model of the two-dimensional graphic after being folded according to the folding reference, including: If the closure type of the three-dimensional open structure is mixed closure, then a coordinate system is constructed for the three-dimensional open structure, and the set of flipped vertices, the set of fixed vertices, and the arc boundary are obtained; Based on the coordinate system, the flipped vertex set, and the fixed vertex set, the vertex correspondence between the flipped vertex set and the fixed vertex set is determined, and the polygonal closed surface of the three-dimensional open structure is constructed based on the vertex correspondence. Based on the arc boundary and the target vertex set, a curved closed surface of the three-dimensional open structure is constructed; wherein, the folded vertex set and the set of vertices in the fixed vertex set that are not on the same plane as the arc boundary are used as the target vertex set; Based on the polygonal closed surface and the curved closed surface, a three-dimensional solid model of the two-dimensional graphic after being folded according to the folding reference is obtained.

[0012] Optionally, based on the arc boundary and the target vertex set, a curved closed surface of the three-dimensional open structure is constructed, including: If the number of vertices in the target vertex set is odd, then connect the midpoint of the target vertex set with the points in the arc boundary to obtain a connecting line; If the number of vertices in the target vertex set is even, then obtain the vertex connection line between the two middle vertices in the target vertex set, and determine the connecting line between the vertex connection line and the arc boundary based on the vertex connection line and the arc boundary. Based on the connecting lines, a curved closed surface of the three-dimensional open structure is constructed.

[0013] Alternatively, methods for generating 3D models may also include: Obtain the model viewing direction corresponding to the three-dimensional model; Based on the observation direction of the model, the observation type of each face in the three-dimensional model is determined; the observation type includes visible and invisible. Based on the observation type of the face adjacent to the model edge in the three-dimensional solid model, the drawing lines of the model edge are determined; wherein the drawing lines include solid lines and dashed lines.

[0014] According to a second aspect of the embodiments of this application, a three-dimensional model generation apparatus is provided, comprising: The folding simulation module is used to perform folding simulation based on a two-dimensional graphic and a folding reference of the two-dimensional graphic to obtain a three-dimensional open structure after folding; wherein, the folding reference includes the folding angle and crease; The closure type determination module is used to determine the closure type for closing a three-dimensional open structure, wherein the closure type includes any one of polygonal closure, surface closure, and hybrid closure of polygons and surfaces; The model generation module is used to perform a closing process on the three-dimensional open structure based on the closing type of the three-dimensional open structure, so as to obtain a three-dimensional solid model after the two-dimensional graphic is folded according to the folding reference.

[0015] According to a third aspect of the embodiments of this application, an electronic device is provided, including: a memory and a processor; The memory is connected to the processor and is used to store programs; The processor is used to implement the above-described method for generating three-dimensional models by running the program in the memory.

[0016] According to a fourth aspect of the embodiments of this application, a computer program product is provided, including computer program instructions, which, when executed by a processor, cause the processor to implement the above-described three-dimensional model generation method.

[0017] The proposed method for generating a three-dimensional model involves performing a folding simulation based on a two-dimensional graphic and its folding reference to obtain a folded three-dimensional open structure. The folding reference includes the folding angle and crease. The method then determines the closure type for the three-dimensional open structure, which can be any one of polygonal closure, surface closure, or a hybrid closure of polygons and surfaces. Based on this closure type, the three-dimensional open structure is closed to obtain a three-dimensional solid model of the two-dimensional graphic folded according to the folding reference. This technical solution automatically closes unclosed open structures after folding, resulting in a closed three-dimensional solid model of the two-dimensional graphic folded according to the folding reference. This improves the visualization of the folded three-dimensional structure and enhances the user's experience in observing the folding effect. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0019] Figure 1 This is a flowchart illustrating a method for generating a 3D model provided in an embodiment of this application.

[0020] Figure 2 This is a schematic diagram of a process for closing a three-dimensional open structure, provided as an embodiment of this application.

[0021] Figure 3 This is a schematic diagram illustrating the generation of a polygonal folded 3D model, as provided in an embodiment of this application.

[0022] Figure 4 This is a schematic diagram illustrating the generation of another polygonal folded stereoscopic model provided in an embodiment of this application.

[0023] Figure 5 This is a schematic diagram illustrating the generation of another polygonal folded stereoscopic model provided in an embodiment of this application.

[0024] Figure 6 This is a schematic diagram illustrating the generation of another polygonal folded stereoscopic model provided in an embodiment of this application.

[0025] Figure 7This is a schematic diagram illustrating the generation of another polygonal folded stereoscopic model provided in an embodiment of this application.

[0026] Figure 8 This is a schematic diagram of another process for closing a three-dimensional open structure, provided as an embodiment of this application.

[0027] Figure 9 A schematic diagram generated for the circular folding three-dimensional model provided in the embodiments of this application.

[0028] Figure 10 This is a schematic diagram of another process for closing a three-dimensional open structure, provided as an embodiment of this application.

[0029] Figure 11 This is a schematic diagram of the generation of a hybrid graphic folding stereoscopic model provided in an embodiment of this application.

[0030] Figure 12 This is a flowchart illustrating another method for generating a three-dimensional model provided in an embodiment of this application.

[0031] Figure 13 This is a schematic diagram of the structure of a three-dimensional model generation device provided in an embodiment of this application.

[0032] Figure 14 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. Detailed Implementation

[0033] The technical solutions of this application are applicable to 3D modeling scenarios. By adopting the technical solutions of this application, open structures formed by folding 2D graphics can be transformed into closed 3D solid structures, improving the visualization effect of 3D solid structures.

[0034] In interdisciplinary fields such as computer graphics, industrial design, and mathematics education, the efficient conversion of two-dimensional designs into three-dimensional models has become a core requirement for driving digital innovation and interdisciplinary practice. This conversion process not only represents a technological leap from abstract concepts to physical visualization but also plays a crucial role in STEM education (science, technology, engineering, and mathematics), maker education, and paper art design. For example, in STEM courses, students need to understand spatial structures and mathematical principles by folding geometric unfolded diagrams; in maker spaces, designers use folded prototypes to quickly verify the feasibility of product forms; and in the field of paper art, artists rely on folding techniques to transform flat patterns into three-dimensional sculptures. These scenarios all require users to complete the two-dimensional to three-dimensional conversion in an intuitive and low-barrier manner, thereby lowering the technical threshold and improving creative and learning efficiency.

[0035] However, existing technologies face significant limitations in practical applications. When users fold a two-dimensional graphic along a specified crease line using software or physical means, the result is often an unclosed open structure with gaps, unclosed edges, or geometric discontinuities on its surface, making it unsuitable as a complete entity for subsequent analysis, manufacturing, or display. Furthermore, the visualization effect of an unclosed open structure is low, affecting the user's observation of the folding effect.

[0036] Therefore, how to transform the open structure formed by folding a two-dimensional graphic into a closed three-dimensional structure to improve the visualization effect is a technical problem that urgently needs to be solved in this field.

[0037] Based on this, this application proposes a method for generating a three-dimensional model. This technical solution can automatically close open structures that are not closed after folding, and obtain a closed three-dimensional model of a two-dimensional graphic after folding according to the folding reference. This solves the problem in the prior art that two-dimensional graphics usually form an open structure that is not closed after folding along the fold line, resulting in low visualization effect and affecting the user's observation of the folding effect.

[0038] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0039] Exemplary methods See Figure 1 As shown in the figure, this application proposes a method for generating a three-dimensional model. The method includes: S101. Based on the two-dimensional graphic and the folding reference of the two-dimensional graphic, a folding simulation is performed to obtain the three-dimensional open structure after folding.

[0040] For two-dimensional graphics that need to be folded, the user also needs to determine the folding reference of the two-dimensional graphics, which includes the folding angle and the crease. This embodiment first needs to obtain the two-dimensional graphics input by the user and the folding reference of the two-dimensional graphics, and then perform a folding simulation on the two-dimensional image according to the folding reference to obtain the folded three-dimensional open structure.

[0041] In this embodiment, the user can input a two-dimensional graphic from existing graphics or draw it manually. The user can input the folding reference by drawing fold lines in the two-dimensional graphic.

[0042] In this embodiment, the folding simulation of the two-dimensional image is performed according to the folding reference of the two-dimensional graphic. This can be achieved using traditional three-dimensional modeling software (such as Blender, 3ds Max, Rhino, etc.) or existing origami simulation software (such as OrigamiSimulator, etc.).

[0043] In addition, this embodiment can also perform simulated folding training on a large model. Two-dimensional graphics and folding references are input into the trained large model, which can then output a folded three-dimensional open structure. The training method for the large model can employ existing methods, which will not be specifically described in this embodiment.

[0044] S102. Determine the type of closure to be applied to the three-dimensional open structure.

[0045] Since different three-dimensional open structures may employ different closure methods, the selection of the closure method for a three-dimensional open structure is based on the type of closure applied. That is, different closure types result in different closure methods. Therefore, this embodiment needs to analyze the closure type applied to the three-dimensional open structure after obtaining the folded structure. The closure types include any one of: polygonal closure, surface closure, and a hybrid closure of polygons and surfaces.

[0046] This embodiment can determine the closure type of a three-dimensional open structure based on the type of the two-dimensional graphic. Specifically, if the two-dimensional graphic is a polygon, the closure type of the three-dimensional open structure is determined to be polygonal closure; if the two-dimensional graphic is a circle or ellipse, the closure type of the three-dimensional open structure is determined to be surface closure; if the two-dimensional graphic is a composite graphic composed of polygons and arcs, the closure type of the three-dimensional open structure is determined to be a hybrid closure of polygons and surfaces. In this embodiment, the type of the two-dimensional graphic can be determined by pre-training a classifier, extracting features from the two-dimensional graphic, and inputting the extracted graphic features into the trained classifier. The classifier classifies the graphic features and outputs the type of the two-dimensional graphic. The training of the classifier first requires collecting sample two-dimensional graphics carrying type labels, then extracting features from the sample two-dimensional graphics, inputting the extracted sample graphic features into the classifier, classifying the sample graphic features, and outputting the sample type of the sample two-dimensional graphic. Finally, the parameters of the classifier are adjusted with the goal of the sample type of the sample two-dimensional graphic being the same as the type label carried by the sample two-dimensional graphic, thereby achieving the training of the classifier.

[0047] This embodiment can also determine the closure type of the three-dimensional open structure based on the geometric properties of the open boundary of the folded three-dimensional open structure. The specific steps are as follows: First, feature extraction is performed on the three-dimensional open structure to obtain structural features, and based on the structural features, the geometric properties of the open boundary of the three-dimensional open structure are determined.

[0048] This embodiment extracts features from a three-dimensional open structure to obtain its structural features. Then, it extracts the boundary features of each open boundary from these structural features. By classifying the boundary features of each open boundary according to their geometric attributes, the geometric attributes of each open boundary are determined. These geometric attributes include polygonal edges or curved edges; that is, if an open boundary is a straight line, its geometric attribute is a polygonal edge, and if an open boundary is a curve, its geometric attribute is a curved edge.

[0049] In this embodiment, geometric attribute classification of the boundary features of open boundaries can be performed by pre-training a geometric attribute classifier. The trained geometric attribute classifier is then used to classify the geometric attributes of the boundary features of open boundaries. Specifically, the training of the geometric attribute classifier involves first collecting sample lines carrying geometric attribute labels, then extracting features from these sample lines to obtain their sample line features. These features are then input into the geometric attribute classifier to obtain the predicted geometric attributes of the sample lines. Finally, the parameters of the geometric attribute classifier are adjusted to ensure that the predicted geometric attributes of the sample lines match their carried geometric attribute labels, thereby achieving the training of the geometric attribute classifier.

[0050] Second, if the geometric properties of all open boundaries of a three-dimensional open structure are polygonal edges, then the closure type corresponding to the three-dimensional open structure is determined to be polygonal closure.

[0051] Third, if the geometric properties of all open boundaries of a three-dimensional open structure are curved edges, then the corresponding closure type of the three-dimensional open structure is determined to be surface closure.

[0052] Fourth, if the three-dimensional open structure includes open boundaries with polygonal edges as geometric properties and open boundaries with curved edges as geometric properties, then the closure type corresponding to the three-dimensional open structure is determined to be a hybrid closure of polygons and surfaces.

[0053] S103. Based on the closed type of the three-dimensional open structure, the three-dimensional development structure is closed to obtain a three-dimensional solid model after the two-dimensional graphic is folded according to the folding reference.

[0054] In this embodiment, after determining the closure type of the three-dimensional open structure, it is necessary to determine the closure processing method of the three-dimensional open structure according to the closure type. The three-dimensional open structure is then closed according to the closure processing method to obtain a three-dimensional solid model after the two-dimensional graphic is folded according to the folding reference.

[0055] The closure type is polygonal closure. The corresponding closure method is to connect the vertices of the folded surface and the vertices of the fixed surface to form multiple polygonal closed surfaces, thereby achieving the closure of the three-dimensional open structure. In this embodiment, the folded surface is the surface that is folded in the three-dimensional open structure, and the fixed surface is the surface that remains stationary in the three-dimensional open structure. The correspondence between the vertices of the folded surface and the vertices of the fixed surface needs to be determined based on the position and order of the vertices. Vertices with corresponding relationships are connected to form multiple polygonal closed surfaces.

[0056] The closure type is curved surface closure. The corresponding closure method is to connect the curved open boundaries in the folded surface with the curved open boundaries in the fixed surface using curves to form a curved closed surface, thereby achieving the closure of the three-dimensional open structure. Specifically, the curve connection between the curved open boundaries on the two surfaces is achieved by extracting arc points from the two arc open boundaries according to the same point extraction ratio, determining the correspondence between the arc points on the two arc open boundaries, and connecting the corresponding arc points using curves (for example, a cycloid can be constructed between two corresponding arc points to achieve the curve connection between the two arc points). This ultimately forms a surface composed of several curves, and all surfaces are smoothed to obtain the curved closed surface.

[0057] The closure type is a hybrid closure of polygons and surfaces. The corresponding closure method is to connect the vertices of the folded surface and the vertices of the fixed surface to form multiple polygonal closed surfaces. It is also necessary to obtain open boundaries with curved edges as arc boundaries. If only one surface in the folded or fixed surface has an arc boundary, then connect that arc boundary to the middle vertex of another surface without an arc boundary, or to the connecting line between two middle vertices, to form several connected surfaces. All surfaces are then smoothed to obtain an arc-shaped closed surface. If both the folded or fixed surface have arc boundaries, then construct an arc-shaped closed surface by combining two arc boundaries in the same way as when the closure type is surface closure. By using multiple polygonal and arc-shaped closed surfaces to close the 3D open structure, a 3D solid model can be obtained.

[0058] As described above, the 3D model generation method proposed in this application, based on a 2D graphic and its folding reference, performs folding simulation to obtain a folded 3D open structure. The folding reference includes the folding angle and crease. The method determines the closure type for the 3D open structure, which includes polygonal closure, surface closure, and a hybrid closure of polygons and surfaces. Based on the closure type of the 3D open structure, the 3D open structure is closed to obtain a 3D solid model of the 2D graphic folded according to the folding reference. Using the technical solution of this embodiment, the unclosed open structure after folding can be automatically closed to obtain a closed 3D solid model of the 2D graphic folded according to the folding reference, improving the visualization effect of the 3D solid structure after folding the 2D graphic and enhancing the user's experience in observing the folding effect.

[0059] As an optional implementation, see [link to implementation details]. Figure 2 As shown, another embodiment of this application discloses that, when the closure type of the three-dimensional open structure is polygonal closure, the three-dimensional open structure is closed based on the closure type of the three-dimensional open structure to obtain a three-dimensional solid model after the two-dimensional graphic is folded according to the folding reference. The specific steps include the following: S201. If the closure type of the three-dimensional open structure is polygonal closure, then construct a coordinate system for the three-dimensional open structure and obtain the set of flipped vertices and the set of fixed vertices.

[0060] When the closure type of the 3D open structure is polygonal closure, this embodiment first needs to construct a coordinate system for the 3D open structure to ensure that the points and lines obtained in the 3D open structure have unified coordinate description information. In this embodiment, the fixed surface (i.e., the surface that has not been folded) in the 3D open structure can be used as the surface constructed by the X-axis and Y-axis in the coordinate system, and the axis perpendicular to the fixed surface can be used as the Z-axis. Furthermore, for the convenience of data calculation, the creases in the 3D open structure can be directly used as the X-axis. This embodiment does not limit the construction of the coordinate system, as long as a fixed coordinate system is constructed.

[0061] This embodiment also requires obtaining the vertices of the folded surfaces (i.e., the surfaces that are folded) in the three-dimensional open structure to form a folded vertex set, and obtaining the vertices of the fixed surfaces in the three-dimensional open structure to form a fixed vertex set. Both the folded vertex set and the fixed vertex set may contain two vertices located on the fold lines, or neither may contain two vertices located on the fold lines. In this embodiment, to improve the generation efficiency of the 3D model and reduce unnecessary work, it is preferable that neither the folded vertex set nor the fixed vertex set contains two vertices located on the fold lines.

[0062] S202. Based on the coordinate system, the flipped vertex set, and the fixed vertex set, determine the vertex correspondence between the flipped vertex set and the fixed vertex set.

[0063] This embodiment requires sorting the vertices in the flipped vertex set and the fixed vertex set according to the coordinate system, using the same sorting rules. Based on the sorted flipped vertex set and fixed vertex set, the correspondence between the vertices in the two sets is determined according to the order of their arrangement. The specific steps are as follows: First, based on the coordinate system, sort the vertices in the flipped vertex set and sort the vertices in the fixed vertex set.

[0064] This embodiment sorts the vertices in the folded vertex set and the fixed vertex set according to a pre-built coordinate system, and the sorting rules for the vertices in the two vertex sets are the same. For example, the horizontal coordinate can be used for sorting; when the crease is used as the horizontal coordinate in the coordinate system, the order of horizontal coordinates from smallest to largest or from largest to smallest is used as the sorting rule for the vertices. Alternatively, the polar angle sorting rule can be used; based on the pre-built coordinate system, the polar angle of each vertex is calculated, and the order of polar angles from smallest to largest or from largest to smallest is used as the sorting rule for the vertices.

[0065] Second, if the number of vertices in the flipped vertex set and the fixed vertex set are different, the vertices in the flipped vertex set are matched with the vertices in the fixed vertex set in order from the edge to the inside to obtain the initial correspondence and the remaining vertices without correspondence.

[0066] This embodiment also needs to determine whether the number of vertices in the flipped vertex set and the fixed vertex set are the same. If the number of vertices is different, it means that a one-to-one correspondence between the vertices in the flipped vertex set and the fixed vertex set cannot be achieved. In this case, the vertices in the flipped vertex set need to be matched with the vertices in the fixed vertex set in order from the edge to the inside to obtain the initial correspondence and the remaining vertices that do not have a correspondence. Specifically, matching the vertices in the flipped vertex set with the vertices in the fixed vertex set in order from the edge to the inside means matching the first vertex in the flipped vertex set with the first vertex in the fixed vertex set, and matching the last vertex in the flipped vertex set with the last vertex in the fixed vertex set; matching the second vertex in the flipped vertex set with the second vertex in the fixed vertex set, and matching the second-to-last vertex in the flipped vertex set with the second-to-last vertex in the fixed vertex set; and so on, until the remaining vertices in the flipped vertex set cannot be matched with the remaining vertices in the fixed vertex set. The vertices that cannot be matched are all considered as remaining vertices. For example, when there is one remaining vertex in the flipped vertex set and multiple remaining vertices in the fixed vertex set, it is impossible to achieve simultaneous correspondence between the first and last vertices. Similarly, when there are zero remaining vertices in the flipped vertex set and one or more remaining vertices in the fixed vertex set, it is also impossible to achieve vertex correspondence.

[0067] Third, according to the vertex order in the flipped vertex set and the fixed vertex set, determine the vertices corresponding to the remaining vertices to obtain the correspondence of the remaining vertices.

[0068] For the remaining vertices, this embodiment needs to determine the vertices corresponding to the remaining vertices according to the order of the vertices in the flipped vertex set and the fixed vertex set, thereby obtaining the correspondence of the remaining vertices. Specifically, when there is one remaining vertex in the first vertex set and multiple remaining vertices in the second vertex set, the remaining vertices in the first vertex set are directly matched with all the remaining vertices in the second vertex set to obtain the correspondence of the remaining vertices. When there are 0 remaining vertices in the first vertex set and one remaining vertex in the second vertex set, the two middle vertices are retrieved from the first vertex set, namely the first vertex and the second vertex, and the remaining vertices in the second vertex set are matched with the first vertex and the second vertex respectively to obtain the correspondence of the remaining vertices. When the first vertex set has 0 remaining vertices, while the second vertex set has multiple remaining vertices, the two middle vertices are retrieved from the first vertex set (i.e., the first and second vertices). The first remaining vertex in the second vertex set is then matched with the first vertex, and the last remaining vertex in the second vertex set is matched with the second vertex. If there is still one remaining vertex in the second vertex set, this remaining vertex is matched with both the first and second vertices. If there are still multiple remaining vertices in the second vertex set, the first remaining vertex in this current state is matched with the first vertex, and the last remaining vertex in this current state is matched with the second vertex, and so on, until all remaining vertices are matched, resulting in the final remaining vertex mapping relationship. Note that when the first vertex set is a folded vertex set, the second vertex set is a fixed vertex set; when the first vertex set is a fixed vertex set, the second vertex set is a folded vertex set.

[0069] Fourth, combine the initial correspondence and the remaining vertex correspondence to obtain the vertex correspondence between the flipped vertex set and the fixed vertex set.

[0070] Fifth, if the number of vertices in the flipped vertex set and the fixed vertex set are the same, then a one-to-one correspondence is made between the vertices in the flipped vertex set and the vertices in the fixed vertex set to obtain the vertex correspondence relationship between the flipped vertex set and the fixed vertex set.

[0071] If the number of vertices in the flipped vertex set and the fixed vertex set are the same, then the vertices in the sorted flipped vertex set and the vertices in the fixed vertex set are matched one-to-one in order to obtain the vertex correspondence between the flipped vertex set and the fixed vertex set.

[0072] S203. Construct a closed surface of a three-dimensional open structure based on vertex correspondence to obtain a three-dimensional solid model of a two-dimensional graphic after folding according to the folding reference.

[0073] In this embodiment, after determining the vertex correspondence between the folded vertex set and the fixed vertex set, the vertices with corresponding relationships are connected according to the vertex correspondence. Mesh information is filled in the area formed by each connecting line and the open boundary, thereby constructing multiple faces. Each constructed face is rendered to obtain the closed face of the three-dimensional open structure, resulting in a three-dimensional solid model of the two-dimensional graphic after being folded according to the folding reference.

[0074] In one specific embodiment, such as Figure 3 As shown, the two-dimensional shape is triangle A1B1C1, with creases a1b1. The closed type of the 3D open structure after folding is polygonal closure. The sorted set of folded vertices is {A1}, and the sorted set of fixed vertices is {B1, C1}. Since the number of vertices in the folded and fixed vertex sets is different, the vertices in the folded vertex set are mapped to the vertices in the fixed vertex set in order from the edge to the inside. The initial mapping is empty, and the remaining vertices without mapping include A1, B1, and C1. If there is one remaining vertex in the folded vertex set and multiple remaining vertices in the fixed vertex set, then the remaining vertex in the folded vertex set is mapped to all the remaining vertices in the fixed vertex set, resulting in the remaining vertex mapping: A1 corresponds to B1, and A1 corresponds to C1. Connecting the vertices according to this mapping yields lines A1B1 and A1C1. Connecting lines A1B1 and A1C1, along with open boundaries A1a1, A1b1, a1B1, b1C1, and B1C1, forms closed surfaces A1a1B1, A1b1C1, and A1B1C1, ultimately constructing a three-dimensional model (such as...). Figure 3 (The third figure in the text).

[0075] In one specific embodiment, such as Figure 4 As shown, the two-dimensional shape is a rectangle A2B2D2C2 with creases a2b2. The closed type of the 3D open structure after folding is a polygonal closure. The sorted set of folded vertices is {A2, B2}, and the sorted set of fixed vertices is {C2, D2}. Since the number of vertices in the folded and fixed vertex sets is the same, a one-to-one correspondence is established between the vertices in the folded and fixed vertex sets, resulting in the vertex correspondence relationship: A2 corresponds to C2, and B2 corresponds to D2. Vertex connections are made according to this correspondence relationship, resulting in lines A2C2 and B2D2. The lines A2C2 and B2D2, along with the open boundaries A2a2, B2b2, a2C2, b2D2, A2B2, and C2D2, can form closed surfaces A2a2C2, B2b2D2, and A2B2C2D2, ultimately constructing a 3D solid model (e.g., ...). Figure 4 (The third figure in the text).

[0076] In one specific embodiment, such as Figure 5As shown, the two-dimensional shape is a heptagon A3B3b3E3D3C3a3, with creases a3b3. The closed type of the folded three-dimensional open structure is a polygonal closure. The sorted set of folded vertices is {A3, B3}, and the sorted set of fixed vertices is {C3, D3, E3}. Since the number of vertices in the folded and fixed vertex sets is different, the vertices in the folded vertex set are matched with the vertices in the fixed vertex set in order from the edge to the inside. The initial correspondence is that A3 corresponds to C3, B3 corresponds to E3, and the remaining vertex without a correspondence is D3. There are 0 vertices remaining in the folded vertex set and 1 vertex remaining in the fixed vertex set. Therefore, the two middle vertices, A3 and B3, are retrieved from the folded vertex set. The remaining vertex D3 in the fixed vertex set is matched with A3 and B3 respectively, resulting in the remaining vertex correspondence: D3 corresponds to A3 and D3 corresponds to B3. Connecting vertices according to this vertex correspondence yields lines A3C3, B3E3, D3A3, and D3B3. These lines, along with open boundaries A3a3, A3B3, B3b3, B3E3, E3D3, D3C3, and C3a3, form closed surfaces A3a3C3, A3C3D3, A3B3D3, B3D3E3, and B3E3b3, ultimately constructing a three-dimensional model (e.g., ...). Figure 5 (The third figure in the text).

[0077] In one specific embodiment, such as Figure 6As shown, the two-dimensional shape is a heptagon A4B4C4G4F4E4D4, with creases a4b4. The closed type of the folded three-dimensional open structure is a polygonal closure. The sorted set of folded vertices is {A4, B4, C4}, and the sorted set of fixed vertices is {D4, E4, F4, G4}. Since the number of vertices in the folded and fixed vertex sets is different, the vertices in the folded vertex set are matched with the vertices in the fixed vertex set in order from the edge to the inside. The initial correspondence is that A4 corresponds to D4, C4 corresponds to G4, and the remaining vertices without a correspondence include B4, E4, and F4. There is one remaining vertex in the folded vertex set and two remaining vertices in the fixed vertex set. Therefore, the remaining vertex B4 in the folded vertex set is directly matched with all the remaining vertices E4 and F4 in the fixed vertex set. The remaining vertex correspondence is that B4 corresponds to E4 and B4 corresponds to F4. Connecting vertices according to this vertex correspondence yields lines A4D4, C4G4, B4E4, and B4F4. These lines, along with open boundaries A4a4, A4B4, B4C4, G4b4, G4F4, F4E4, E4D4, and D4a4, form closed surfaces A4a4D4, A4B4E4D4, B4E4F4, B4C4G4F4, and C4G4b4, ultimately constructing a three-dimensional model (e.g., ...). Figure 6 (The third figure in the text).

[0078] In one specific embodiment, such as Figure 7 As shown, the two-dimensional shape is a hexagon A5B5C5F5E5D5, with creases a5b5. The closed type of the folded three-dimensional open structure is polygonal closure. The sorted set of folded vertices is {A5, B5, C5}, and the sorted set of fixed vertices is {D5, E5, F5}. Since the number of vertices in the folded and fixed vertex sets is the same, a one-to-one correspondence is established between the vertices in the folded and fixed vertex sets. The resulting vertex correspondences are: A5 corresponds to D5, B5 corresponds to E5, and C5 corresponds to F5. Connecting the vertices according to this correspondence yields lines A5D5, C5F5, and B5E5. Connecting lines A5D5, C5F5, and B5E5, along with open boundaries A5a5, A5B5, B5C5, C5b5, b5F5, F5E5, E5D5, and D5a5, can form closed surfaces A5a5D5, C5b5F5, A5B5E5D5, and B5C5F5E5, ultimately constructing a three-dimensional model (such as...). Figure 7 (The third figure in the text).

[0079] As an optional implementation, see [link to implementation details]. Figure 8As shown, another embodiment of this application discloses that, when the closure type of the three-dimensional open structure is curved surface closure, the three-dimensional open structure is closed based on the closure type of the three-dimensional open structure to obtain a three-dimensional solid model after the two-dimensional graphic is folded according to the folding reference. The specific steps include the following: S801. If the closure type of the three-dimensional open structure is curved surface closure, then obtain the first arc of the folded surface in the three-dimensional open structure and the second arc of the fixed surface in the three-dimensional open structure.

[0080] In the case where the closure type of the three-dimensional open structure is curved surface closure, this embodiment first needs to obtain the open boundary in the three-dimensional open structure, take the open boundary of the folded surface in the three-dimensional open structure as the first arc, and take the open boundary of the fixed surface in the three-dimensional open structure as the second arc.

[0081] S802. Based on the first arc and the second arc, determine the connection curve between the first arc and the second arc.

[0082] This embodiment requires extracting arc points from the first and second arcs, determining the correspondence between arc points in the first and second arcs, and connecting the corresponding arc points with curves to obtain all the connecting curves between the first and second arcs. The specific steps are as follows: First, according to the point extraction ratio, select the first arc point in the first arc and the second arc point in the second arc, and make a one-to-one correspondence between the first arc point and the second arc point to obtain the point correspondence relationship.

[0083] This embodiment requires pre-setting the point extraction ratio, and then selecting the first arc point in the first arc and the second arc point in the second arc according to the point extraction ratio. When the point extraction ratio is set to 50%, a first arc point is collected at the 50% position (midpoint) of the first arc, and a second arc point is collected at the 50% position (midpoint) of the second arc. When the point extraction ratio is set to 20%, a first arc point is collected at the 20%, 40%, 60%, and 80% positions of the first arc, and a second arc point is collected at the 20%, 40%, 60%, and 80% positions of the second arc. When the point extraction ratio is set to 10%, a first arc point is collected at the 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90% positions of the first arc, and a second arc point is collected at the 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90% positions of the second arc. The smaller the point extraction ratio is set, the more arc points are collected, the more connection curves are obtained, and the more accurate the closed surface is constructed.

[0084] Because the point extraction ratio for the first and second arcs is the same, the number of extracted points on the first arc is the same as the number of points on the second arc. This allows for a one-to-one correspondence between the first and second arc points based on their positions on the arcs. For example, when the point extraction ratio is set to 20%, the first arc point at the 20% position of the first arc corresponds to the second arc point at the 20% position of the second arc; the first arc point at the 40% position of the first arc corresponds to the second arc point at the 40% position of the second arc; the first arc point at the 60% position of the first arc corresponds to the second arc point at the 60% position of the second arc; and the first arc point at the 80% position of the first arc corresponds to the second arc point at the 80% position of the second arc.

[0085] Second, based on the point correspondence, construct cycloids between corresponding points to obtain the connection curve between the first and second arcs.

[0086] After determining the point correspondence between the arc points in the first arc and the arc points in the second arc, a cycloid is constructed between the corresponding arc points. Snell's law can be used to construct the cycloid between two arc points. In this embodiment, all cycloids between corresponding arc points are used as the connecting curve between the first and second arcs.

[0087] S803. Based on the connection curve between the first and second arcs, construct the closed surface of the three-dimensional open structure to obtain a three-dimensional solid model of the two-dimensional graphic after folding according to the folding reference.

[0088] Based on the connecting curves between the first and second arcs, mesh information is filled into the areas between all curves, and then smoothed and rendered to obtain a smooth, closed arc surface. It can be seen that the more connecting curves there are between the first and second arcs, the closer the surface formed by all the curves is to a smooth surface, and the more accurate the closed arc surface obtained after smoothing and rendering. By constructing a closed arc surface for a 3D open structure, a 3D model of a 2D graphic folded according to a folding reference can be obtained.

[0089] As an optional implementation, when the closure type of the three-dimensional open structure is curved surface closure, and the two-dimensional graphic is a circle with the crease being the diameter of the circle, this embodiment can directly use the center of the circle as the center of the sphere and the radius of the circle as the basic radius of the sphere to generate a complete sphere. Then, using the two open boundaries of the three-dimensional solid structure as trimming boundaries, the sphere is trimmed (using Boolean operations), retaining the spherical crown portion located inside the two open boundaries. This spherical crown portion is then meshed and stitched with the three-dimensional solid structure, thereby obtaining a three-dimensional solid model after the two-dimensional graphic is folded according to the folding reference. This method of generating a three-dimensional solid model is more efficient and accurate than the generation method used in the above embodiment, but this method is only applicable to the case where the two-dimensional graphic is a circle with the crease being the diameter of the circle.

[0090] In one specific embodiment, such as Figure 9 As shown, the two-dimensional graphic is a circle with creases a6 and b6. The closed type of the three-dimensional open structure after folding is a curved surface closure. The first arc point extracted from the first arc is A5 and B5, and the second arc point extracted from the second arc is C5 and D5, where A5 corresponds to C5, and B5 corresponds to D5. A cycloid is constructed between A5 and C5, and between B5 and D5. Mesh information is filled into the cycloid, the area between the first arc, and the second arc, and then smoothed to obtain the curved closed surface, thus constructing a three-dimensional model (such as...). Figure 9 (The third figure in the text). Due to Figure 9 The two-dimensional graphic in the image is a circle, and the crease a6b6 is the diameter of the circle. Therefore, a sphere can be constructed directly using the center of this circle as the center and the crease a6b6 as the basic diameter of the sphere. Then, the two open boundaries of the three-dimensional structure are used as cutting boundaries to cut the sphere, retaining the spherical crown portion located inside the two open boundaries. This spherical crown portion is then meshed and stitched to the three-dimensional structure, thus obtaining a three-dimensional model of the two-dimensional graphic after folding according to the folding reference (e.g., ...). Figure 9(The third figure in the text).

[0091] As an optional implementation, see [link to implementation details]. Figure 10 As shown, in another embodiment of this application, when the closure type of the three-dimensional open structure is a hybrid closure of polygons and surfaces, the three-dimensional open structure is closed based on its closure type to obtain a three-dimensional solid model after the two-dimensional graphic is folded according to the folding reference. The specific steps include the following: S111. If the closure type of the three-dimensional open structure is mixed closure, then construct a coordinate system for the three-dimensional open structure and obtain the set of flipped vertices, the set of fixed vertices, and the arc boundary.

[0092] If the closure type of the 3D open structure is a hybrid model, then it is necessary to construct a coordinate system for the 3D open structure, obtain the flipped vertex set and the fixed vertex set, and also obtain the open boundary of the 3D open structure as an arc boundary. The acquisition of the flipped vertex set, the fixed vertex set, and the arc boundary has been specifically described in the above embodiments, and will not be repeated in this embodiment.

[0093] S112. Based on the coordinate system, the flipped vertex set, and the fixed vertex set, determine the vertex correspondence between the flipped vertex set and the fixed vertex set, and construct the polygonal closed surface of the three-dimensional open structure based on the vertex correspondence.

[0094] This embodiment determines the vertex correspondence between the flipped vertex set and the fixed vertex set based on a coordinate system, a flipped vertex set, and a fixed vertex set, and constructs a polygonal closed surface of a three-dimensional open structure based on the vertex correspondence. The specific execution method of this step has been described in detail in the above embodiments, and will not be repeated here.

[0095] S113. Based on the arc boundary and the target vertex set, construct the closed surface of the three-dimensional open structure.

[0096] In the case where only one plane in the folded surface and fixed surface of the three-dimensional solid structure has an arc boundary, this embodiment uses the set of vertices that are not on the same plane as the arc boundary as the target vertex set. That is, when the arc boundary is on the folded surface of the three-dimensional solid structure, the fixed vertex set is used as the target vertex set, and when the arc boundary is on the fixed surface of the three-dimensional solid structure, the folded vertex set is used as the target vertex set.

[0097] From the set of target vertices, determine the target vertices or the lines connecting them to the arc boundary. Then, connect each point in the arc boundary to the target vertices to obtain connecting lines. Alternatively, extract arc points and line segment points from the lines connecting the arc boundary and vertices according to the point extraction ratio. Then, sequentially map the arc points to the line segment points, and connect the corresponding arc points to the line segment points to obtain connecting lines. Based on the obtained connecting lines, construct the closed surface of the three-dimensional open structure, i.e., the arc-shaped closed surface. The specific steps are as follows: First, if the number of vertices in the target vertex set is odd, then connect the midpoint of the target vertex set with the points in the arc boundary to obtain the connecting line.

[0098] If the number of vertices in the target vertex set is odd, then the midpoint of the target vertex set is taken as the target vertex, at least one arc point is extracted from the arc boundary, and the target vertex is connected to each arc point to obtain at least one connecting line.

[0099] Second, if the number of vertices in the target vertex set is even, then obtain the vertex connection between the two middle vertices in the target vertex set, and determine the connecting line between the vertex connection and the arc boundary based on the vertex connection and the arc boundary. If the number of vertices in the target vertex set is even, then the connecting line between the two middle vertices in the target vertex set is obtained as the vertex connection line. Then, according to the point extraction ratio, line segment points are extracted from the vertex connection line, and arc point points are extracted from the arc boundary. Since the point extraction is performed according to the same point extraction ratio, the number of extracted line segment points and arc point points is the same. The method of point extraction according to the point extraction ratio has been specifically described in the above embodiments, and will not be repeated in this embodiment.

[0100] By sequentially mapping the arc points to the line segment points, and connecting the corresponding arc points to the line segment points, we obtain the connecting lines between the vertex lines and the arc boundaries.

[0101] Third, based on the connecting lines, construct a closed surface of a three-dimensional open structure.

[0102] The area formed between all connecting lines and the curved boundary is filled with mesh information, and then smoothed and rendered to obtain a smooth curved closed surface, which is the curved closed surface. It can be seen that the more connecting lines there are, the closer the surface formed by all connecting lines and the curved boundary is to a smooth curved surface, and the more accurate the curved closed surface obtained by smoothing and rendering is.

[0103] When both the folded and fixed surfaces of a three-dimensional structure contain curved boundaries, the curved boundary in the folded surface is directly taken as the first arc, and the curved boundary in the fixed surface is taken as the second arc. Based on the first and second arcs, a connection curve between the first and second arcs is determined. Based on this connection curve, a curved closed surface of the three-dimensional open structure, i.e., an arc-shaped closed surface, is constructed. The specific execution method of this step has been described in detail in the above embodiments and will not be repeated here.

[0104] S114. Based on the polygonal closed surface and the curved closed surface, obtain the three-dimensional solid model of the two-dimensional graphic after folding according to the folding reference.

[0105] The above steps can construct polygonal closed surfaces and curved closed surfaces on a three-dimensional open structure. In this embodiment, it is also necessary to locally smooth the seam between the constructed polygonal closed surfaces and curved closed surfaces on the three-dimensional open structure, so as to form a unified, manifold whole and obtain a three-dimensional solid model after the two-dimensional graphic is folded according to the folding reference.

[0106] In one specific embodiment, such as Figure 11As shown, the two-dimensional graphic is a patchwork of polygons and arcs, A7B7C7E7D7, with creases a7b7. The closed type of the folded three-dimensional open structure is a hybrid closure of polygons and curved surfaces. The sorted set of folded vertices is {A7, B7, C7}, and the sorted set of fixed vertices is {D7, E7}. Since the number of vertices in the folded and fixed vertex sets is different, the vertices in the folded vertex set are matched with the vertices in the fixed vertex set in order from the edge to the inside. The initial correspondence is that A7 corresponds to D7, C7 corresponds to E7, and the remaining vertex without a correspondence is B7. There is one remaining vertex in the folded vertex set and zero remaining vertices in the fixed vertex set. Therefore, the two middle vertices, D7 and E7, are retrieved from the fixed vertex set. The remaining vertex B7 in the folded vertex set is matched with D7 and E7 respectively, resulting in the remaining vertex correspondence: B7 corresponds to D7 and B7 corresponds to E7. Connecting vertices according to this vertex correspondence yields lines A7D7, C7E7, B7D7, and B7E7. These lines, along with the open boundaries A7a7, A7B7, B7C7, b7C7, b7E7, and D7a7, can form the polygonal closed surfaces A7a7D7, A7B7D7, B7E7C7, and C7E7b7. Obtain the arc boundary D7E7, which is located on a fixed surface. There is no arc boundary in the folded surface. Use the folded vertex set as the target vertex set. The target vertex set includes 3 vertices (an odd number). Then, take the midpoint B7 of the target vertex set as the target vertex. Connect target vertex B7 to the points in the arc boundary D7E7 to obtain connecting lines. Fill the area formed between all connecting lines and the arc boundary D7E7 with mesh information, and perform smoothing and rendering to obtain a smooth arc-shaped closed surface. This arc-shaped closed surface is the curved closed surface. Based on the polygonal closed surface and the curved closed surface, obtain the three-dimensional model of the 2D graphic after folding according to the folding reference (e.g., ...). Figure 11 (The third figure in the text).

[0107] As an optional implementation, this application also proposes a method for generating a three-dimensional model. See [link to relevant documentation]. Figure 12 As shown, the method for generating 3D models may also include: S121. Obtain the model observation direction corresponding to the three-dimensional model.

[0108] This embodiment requires determining the viewing direction of the 3D model based on its current display angle. This embodiment can utilize existing 3D software (such as AutoCAD, 3DS Max, etc.) to determine the viewing direction of the 3D model, which will not be elaborated upon further in this embodiment.

[0109] S122. Based on the model's observation direction, determine the observation type of each face in the three-dimensional solid model.

[0110] Based on the model's viewing direction, determine whether each face in the 3D model is visible. Specifically, observe each face in the 3D model according to the model's viewing direction. If it can be seen, the face is determined to be visible, and its observation type is set to visible. If it cannot be seen, the face is determined to be invisible, and its observation type is set to invisible.

[0111] Specifically, in this embodiment, the angle between the normal vector of the surface and the viewing direction of the model can be determined by calculating the normal vector of the surface. If the angle is greater than or equal to 90 degrees, the viewing type of the surface is determined to be visible. If the angle is less than 90 degrees, the viewing type of the surface is determined to be invisible.

[0112] S123. Based on the observation type of the face adjacent to the model edge in the three-dimensional solid model, determine the drawing lines of the model edge.

[0113] To determine the drawing lines for each model edge in a 3D solid model, we can first determine the two faces adjacent to the model edge. If the observation type of both faces adjacent to the model edge is invisible, then the model edge is determined to be a hidden contour edge, and the drawing line is a dashed line. If at least one of the two faces adjacent to the model edge is visible, then the model edge is determined to be a visible contour edge, and the drawing line is a solid line.

[0114] This embodiment uses solid lines to draw the visible outline edges in the 3D model and dashed lines to draw the hidden outline edges. This makes the front edges appear as solid lines and the back, occluded edges appear as dashed lines, greatly enhancing the three-dimensionality, readability, and professional drawing representation of the 3D model.

[0115] In addition, for the curved model edge in the 3D model, it can be composed of two repeated drawing lines, one solid line and one dashed line. Based on the model viewing direction, the dashed line in the area that can be directly illuminated by the model viewing direction is hidden and the solid line is directly displayed. The solid line in the area that cannot be illuminated by the model viewing direction is hidden and the dashed line is directly displayed.

[0116] As an optional implementation, this application also proposes a method for generating a 3D model. The method for generating a 3D model may further include: First, based on a three-dimensional open structure and a three-dimensional solid model, an animation is constructed that transforms the three-dimensional open structure into a three-dimensional solid structure.

[0117] This embodiment uses the 3D open structure as the initial frame of the animation and the 3D solid model as the ending frame. Then, based on the differences between the 3D open structure and the 3D solid model, several intermediate frames are constructed. These intermediate frames can be constructed according to the calculation order in which the 3D solid model is generated from the 3D open structure. For example, for a polygonal closed animation, the image after connecting the vertices of the folded face and the fixed face is used as the first intermediate frame, and the image of the area formed by the connecting lines and the open boundary filled with a mesh is used as the second intermediate frame, and so on. After constructing several image frames, an animation is created, or interpolation is performed within the animation to generate a smoother animation. Demonstrating the generation process of the 3D solid model through animation transforms the graphical display into an intuitive visual demonstration, improving the visualization effect.

[0118] Exemplary device Accordingly, this application also provides a 3D model generation device, see [link to relevant documentation]. Figure 13 As shown, the device includes: The folding simulation module 100 is used to perform folding simulation based on two-dimensional graphics and folding references of the two-dimensional graphics to obtain the three-dimensional open structure after folding; wherein, the folding references include folding angles and creases; The closure type determination module 110 is used to determine the closure type for closing the three-dimensional open structure, wherein the closure type includes any one of polygon closure, surface closure and hybrid closure of polygon and surface; The model generation module 120 is used to close the three-dimensional open structure based on the closed type of the three-dimensional open structure, and obtain the three-dimensional solid model after the two-dimensional graphic is folded according to the folding reference.

[0119] As can be seen from the above description, the stereoscopic model generation device proposed in this application can automatically close open structures that are not closed after folding, and obtain a closed three-dimensional stereoscopic model of a two-dimensional graphic after folding according to the folding reference. This improves the visualization effect of the three-dimensional stereoscopic structure after folding the two-dimensional graphic and enhances the user's experience in observing the folding effect.

[0120] As an optional implementation, another embodiment of this application discloses that the closure type determination module 110 is specifically used for: Feature extraction is performed on the three-dimensional open structure to obtain structural features, and based on the structural features, the geometric properties of the open boundary of the three-dimensional open structure are determined; wherein, the geometric properties include: polygonal edges or curved edges; If the geometric properties of all open boundaries of a 3D open structure are polygonal edges, then the closure type of the 3D open structure is determined to be polygonal closure. If the geometric properties of all open boundaries of a three-dimensional open structure are curved edges, then the closure type corresponding to the three-dimensional open structure is determined to be surface closure. If a three-dimensional open structure includes open boundaries with polygonal edges as geometric properties and open boundaries with curved edges as geometric properties, then the closure type corresponding to the three-dimensional open structure is determined to be a hybrid closure of polygons and surfaces.

[0121] As an optional implementation, another embodiment of this application discloses that the model generation module 120 includes: an acquisition unit, a first determination unit, and a closed surface determination unit.

[0122] The acquisition unit is used to construct a coordinate system for the three-dimensional open structure if the closure type of the three-dimensional open structure is polygonal closure, and to acquire the set of flipped vertices and the set of fixed vertices; wherein, the set of flipped vertices contains the vertices of the flipped surfaces in the three-dimensional open structure, and the set of fixed vertices contains the vertices of the fixed surfaces in the three-dimensional open structure. The first determining unit is used to determine the vertex correspondence between the flipped vertex set and the fixed vertex set based on the coordinate system, the flipped vertex set, and the fixed vertex set; The closed surface determination unit is used to construct the closed surface of a three-dimensional open structure based on the vertex correspondence, and obtain a three-dimensional solid model after the two-dimensional graphic is folded according to the folding reference.

[0123] As an optional implementation, another embodiment of this application discloses a first determining unit, specifically used for: Based on the coordinate system, sort the vertices in the flipped vertex set and sort the vertices in the fixed vertex set; If the number of vertices in the flipped vertex set and the fixed vertex set are different, then the vertices in the flipped vertex set are matched with the vertices in the fixed vertex set in order from the edge to the inside, to obtain the initial correspondence and the remaining vertices without correspondence. Based on the vertex order in the flipped vertex set and the fixed vertex set, determine the vertices corresponding to the remaining vertices to obtain the correspondence of the remaining vertices; By combining the initial correspondence and the remaining vertex correspondence, we obtain the vertex correspondence between the flipped vertex set and the fixed vertex set; If the number of vertices in the flipped vertex set and the fixed vertex set are the same, then a one-to-one correspondence is established between the vertices in the flipped vertex set and the vertices in the fixed vertex set to obtain the vertex correspondence relationship between the flipped vertex set and the fixed vertex set.

[0124] As an optional implementation, another embodiment of this application discloses that the acquisition unit is further configured to acquire the first arc of the folded surface and the second arc of the fixed surface in the three-dimensional open structure if the closure type of the three-dimensional open structure is curved surface closure. The first determining unit is also used to determine the connection curve between the first arc and the second arc based on the first arc and the second arc. The closed surface determination unit is also used to construct the closed surface of a three-dimensional open structure based on the connection curve between the first arc and the second arc, so as to obtain a three-dimensional solid model of the two-dimensional graphic after being folded according to the folding reference.

[0125] As an optional implementation, another embodiment of this application discloses a first determining unit, which is specifically further used for: According to the point extraction ratio, select the first arc point in the first arc and the second arc point in the second arc, and make a one-to-one correspondence between the first arc point and the second arc point to obtain the point correspondence relationship; Based on the point correspondence, construct cycloids between corresponding points to obtain the connection curve between the first and second arcs.

[0126] As an optional implementation, another embodiment of this application discloses that the acquisition unit is further configured to construct a coordinate system for the three-dimensional open structure and acquire the set of flipped vertices, the set of fixed vertices, and the arc boundary if the closure type of the three-dimensional open structure is a mixed closure. The first determining unit is also used to determine the vertex correspondence between the flipped vertex set and the fixed vertex set based on the coordinate system, the flipped vertex set and the fixed vertex set, and to construct the polygonal closed surface of the three-dimensional open structure based on the vertex correspondence. The closed surface determination unit is also used to construct a curved closed surface of a three-dimensional open structure based on the arc boundary and the target vertex set; wherein, the vertex set of the flipped vertex set and the vertex set of the fixed vertex set that are not on the same plane as the arc boundary are used as the target vertex set; based on the polygonal closed surface and the curved closed surface, a three-dimensional solid model of the two-dimensional graphic after flipping according to the flipping reference is obtained.

[0127] As an optional implementation, another embodiment of this application discloses a closed surface determining unit, specifically used for: If the number of vertices in the target vertex set is odd, then connect the midpoint of the target vertex set with the points in the arc boundary to obtain the connecting line; If the number of vertices in the target vertex set is even, then obtain the vertex connection between the two middle vertices in the target vertex set, and determine the connection line between the vertex connection and the arc boundary based on the vertex connection and the arc boundary. Based on the connecting lines, construct a closed surface of a three-dimensional open structure.

[0128] As an optional implementation, another embodiment of this application discloses that the 3D model generation device further includes: a direction acquisition module, a type determination module, and a line determination module.

[0129] The orientation acquisition module is used to obtain the viewing orientation of the 3D model. The type determination module is used to determine the observation type of each face in the 3D model based on the model's observation direction; the observation type includes visible and invisible. The line determination module is used to determine the drawing lines of the model edges based on the observation type of the faces adjacent to the model edges in the 3D solid model; the drawing lines include solid lines and dashed lines.

[0130] The stereoscopic model generation apparatus provided in this embodiment belongs to the same concept as the stereoscopic model generation method provided in the above embodiments of this application. It can execute the stereoscopic model generation method provided in any of the above embodiments of this application and has the corresponding functional modules and beneficial effects for executing the stereoscopic model generation method. Technical details not described in detail in this embodiment can be found in the specific processing content of the stereoscopic model generation method provided in the above embodiments of this application, and will not be repeated here.

[0131] Exemplary electronic devices Another embodiment of this application also provides an electronic device, see [link to relevant documentation] Figure 14 As shown, the device includes: Memory 200 and processor 210; The memory 200 is connected to the processor 210 and is used to store programs; The processor 210 is used to implement the stereo model generation method disclosed in any of the above embodiments by running the program stored in the memory 200.

[0132] Specifically, the aforementioned electronic device may also include: a bus, a communication interface 220, an input device 230, and an output device 240.

[0133] The processor 210, memory 200, communication interface 220, input device 230, and output device 240 are interconnected via a bus. Among them: A bus can include a pathway for transmitting information between various components of a computer system.

[0134] Processor 210 can be a general-purpose processor, such as a general-purpose central processing unit (CPU), a microprocessor, etc., or an application-specific integrated circuit (ASIC), or one or more integrated circuits used to control the execution of the program of the present invention. It can also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), an off-the-shelf programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0135] Processor 210 may include a main processor, as well as a baseband chip, modem, etc.

[0136] The memory 200 stores a program that executes the technical solution of this invention, and may also store an operating system and other key business functions. Specifically, the program may include program code, which includes computer operation instructions. More specifically, the memory 200 may include read-only memory (ROM), other types of static storage devices capable of storing static information and instructions, random access memory (RAM), other types of dynamic storage devices capable of storing information and instructions, disk storage, flash memory, etc.

[0137] Input device 230 may include a device for receiving user input data and information, such as a keyboard, mouse, camera, scanner, light pen, voice input device, touch screen, pedometer, or gravity sensor.

[0138] Output device 240 may include devices that allow information to be output to a user, such as a display screen, printer, speaker, etc.

[0139] The communication interface 220 may include a device that uses any transceiver to communicate with other devices or communication networks, such as Ethernet, Radio Access Network (RAN), Wireless Local Area Network (WLAN), etc.

[0140] The processor 210 executes the program stored in the memory 200 and calls other devices, and can be used to implement each step of any of the three-dimensional model generation methods provided in the above embodiments of this application.

[0141] Exemplary computer program products and storage media In addition to the methods and devices described above, embodiments of this application may also be computer program products, which include computer program instructions that, when executed by a processor, cause the processor to perform the steps in the stereoscopic model generation methods according to various embodiments of this application as described in the "Exemplary Methods" section of this specification.

[0142] The computer program product can be written in any combination of one or more programming languages ​​to perform the operations of the embodiments of this application. The programming languages ​​include object-oriented programming languages ​​such as Java and C++, as well as conventional procedural programming languages ​​such as C or similar languages. The program code can be executed entirely on the user's computing device, partially on the user's computing device, as a standalone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server.

[0143] Furthermore, embodiments of this application may also be storage media storing a computer program, which is executed by a processor in the steps of the stereoscopic model generation method according to various embodiments of this application described in the "Exemplary Methods" section above.

[0144] For the foregoing method embodiments, in order to simplify the description, they are all described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, because according to this application, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily essential to this application.

[0145] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For apparatus embodiments, since they are basically similar to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0146] The steps in the methods of the various embodiments of this application can be adjusted, merged, or deleted in order according to actual needs, and the technical features described in each embodiment can be replaced or combined.

[0147] The modules and sub-modules in the various embodiments of the present application's devices and terminals can be merged, divided, and deleted according to actual needs.

[0148] It should be understood that the disclosed terminals, devices, and methods can be implemented in other ways, given the several embodiments provided in this application. For example, the terminal embodiments described above are merely illustrative. For instance, the division of modules or sub-modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple sub-modules or modules may be combined or integrated into another module, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, devices, or modules, and may be electrical, mechanical, or other forms.

[0149] The modules or submodules described as separate components may or may not be physically separate. The components that constitute a module or submodule may or may not be physical modules or submodules; that is, they may be located in one place or distributed across multiple network modules or submodules. Some or all of the modules or submodules can be selected to achieve the purpose of this embodiment's solution, depending on actual needs.

[0150] Furthermore, the functional modules or sub-modules in the various embodiments of this application can be integrated into one processing module, or each module or sub-module can exist physically separately, or two or more modules or sub-modules can be integrated into one module. The integrated modules or sub-modules described above can be implemented in hardware or in the form of software functional modules or sub-modules.

[0151] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0152] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software unit executed by a processor, or a combination of both. The software unit can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0153] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0154] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for generating a three-dimensional model, characterized in that, include: Based on the two-dimensional graphic and the folding reference of the two-dimensional graphic, a folding simulation is performed to obtain the three-dimensional open structure after folding; wherein, the folding reference includes the folding angle and the crease; Determine the closure type for closing the three-dimensional open structure, wherein the closure type includes any one of polygonal closure, surface closure, and hybrid closure of polygons and surfaces; Based on the closure type of the three-dimensional open structure, the three-dimensional open structure is closed to obtain a three-dimensional solid model after the two-dimensional graphic is folded according to the folding reference.

2. The method according to claim 1, characterized in that, Determine the closure type for closing a three-dimensional open structure, including: Feature extraction is performed on the three-dimensional open structure to obtain structural features, and based on the structural features, the geometric properties of the open boundary of the three-dimensional open structure are determined; wherein, the geometric properties include: polygonal edges or curved edges; If the geometric properties of all open boundaries of the three-dimensional open structure are polygonal edges, then the closure type corresponding to the three-dimensional open structure is determined to be polygonal closure. If the geometric properties of all open boundaries of the three-dimensional open structure are curved edges, then the closure type corresponding to the three-dimensional open structure is determined to be surface closure. If the three-dimensional open structure includes open boundaries with polygonal edges as geometric attributes and open boundaries with curved edges as geometric attributes, then the closure type corresponding to the three-dimensional open structure is determined to be a hybrid closure of polygons and surfaces.

3. The method according to claim 1, characterized in that, Based on the closure type of the three-dimensional open structure, the three-dimensional open structure is closed to obtain a three-dimensional solid model of the two-dimensional graphic after being folded according to the folding reference, including: If the closure type of the three-dimensional open structure is polygonal closure, then a coordinate system is constructed for the three-dimensional open structure, and a set of flipped vertices and a set of fixed vertices are obtained; wherein, the set of flipped vertices contains the vertices of the flipped surfaces in the three-dimensional open structure, and the set of fixed vertices contains the vertices of the fixed surfaces in the three-dimensional open structure; Based on the coordinate system, the flipped vertex set, and the fixed vertex set, determine the vertex correspondence between the flipped vertex set and the fixed vertex set; Based on the vertex correspondence, the closed surface of the three-dimensional open structure is constructed to obtain the three-dimensional solid model after the two-dimensional graphic is folded according to the folding reference.

4. The method according to claim 3, characterized in that, Based on the coordinate system, the flipped vertex set, and the fixed vertex set, determine the vertex correspondence between the flipped vertex set and the fixed vertex set; Based on the coordinate system, the vertices in the flipped vertex set are sorted, and the vertices in the fixed vertex set are sorted. If the number of vertices in the flipped vertex set and the fixed vertex set are different, then the vertices in the flipped vertex set and the vertices in the fixed vertex set are matched in order from the edge to the inside to obtain the initial matching relationship and the remaining vertices without matching relationship; According to the vertex order of the flipped vertex set and the fixed vertex set, determine the vertices corresponding to the remaining vertices to obtain the correspondence of the remaining vertices; The initial correspondence and the remaining vertex correspondence are combined to obtain the vertex correspondence between the flipped vertex set and the fixed vertex set; If the number of vertices in the flipped vertex set and the fixed vertex set are the same, then a one-to-one correspondence is established between the vertices in the flipped vertex set and the vertices in the fixed vertex set to obtain the vertex correspondence relationship between the flipped vertex set and the fixed vertex set.

5. The method according to claim 1, characterized in that, Based on the closure type of the three-dimensional open structure, the three-dimensional open structure is closed to obtain a three-dimensional solid model of the two-dimensional graphic after being folded according to the folding reference, including: If the closure type of the three-dimensional open structure is curved surface closure, then obtain the first arc of the folded surface in the three-dimensional open structure and the second arc of the fixed surface in the three-dimensional open structure; Based on the first arc and the second arc, determine the connection curve between the first arc and the second arc; Based on the connection curve between the first arc and the second arc, the closed surface of the three-dimensional open structure is constructed to obtain the three-dimensional solid model of the two-dimensional graphic after being folded according to the folding reference.

6. The method according to claim 5, characterized in that, Based on the first arc and the second arc, determine the connection curve between the first arc and the second arc, including: According to the point extraction ratio, select the first arc point in the first arc and the second arc point in the second arc, and make a one-to-one correspondence between the first arc point and the second arc point to obtain the point correspondence relationship; Based on the point correspondence, a cycloid is constructed between the corresponding points to obtain the connection curve between the first arc and the second arc.

7. The method according to claim 1, characterized in that, Based on the closure type of the three-dimensional open structure, the three-dimensional open structure is closed to obtain a three-dimensional solid model of the two-dimensional graphic after being folded according to the folding reference, including: If the closure type of the three-dimensional open structure is mixed closure, then a coordinate system is constructed for the three-dimensional open structure, and the set of flipped vertices, the set of fixed vertices, and the arc boundary are obtained; Based on the coordinate system, the flipped vertex set, and the fixed vertex set, the vertex correspondence between the flipped vertex set and the fixed vertex set is determined, and the polygonal closed surface of the three-dimensional open structure is constructed based on the vertex correspondence. Based on the arc boundary and the target vertex set, a curved closed surface of the three-dimensional open structure is constructed; wherein, the folded vertex set and the set of vertices in the fixed vertex set that are not on the same plane as the arc boundary are used as the target vertex set; Based on the polygonal closed surface and the curved closed surface, a three-dimensional solid model of the two-dimensional graphic after being folded according to the folding reference is obtained.

8. The method according to claim 7, characterized in that, Based on the arc boundary and the target vertex set, the surface closure of the three-dimensional open structure is constructed, including: If the number of vertices in the target vertex set is odd, then connect the midpoint of the target vertex set with the points in the arc boundary to obtain a connecting line; If the number of vertices in the target vertex set is even, then obtain the vertex connection line between the two middle vertices in the target vertex set, and determine the connecting line between the vertex connection line and the arc boundary based on the vertex connection line and the arc boundary. Based on the connecting lines, a curved closed surface of the three-dimensional open structure is constructed.

9. The method according to claim 1, characterized in that, Also includes: Obtain the model viewing direction corresponding to the three-dimensional model; Based on the observation direction of the model, the observation type of each face in the three-dimensional model is determined; the observation type includes visible and invisible. Based on the observation type of the face adjacent to the model edge in the three-dimensional solid model, determine the drawing lines of the model edge; The lines drawn include solid lines and dashed lines.

10. A three-dimensional model generation device, characterized in that, include: The folding simulation module is used to perform folding simulation based on a two-dimensional graphic and a folding reference of the two-dimensional graphic to obtain a three-dimensional open structure after folding; wherein, the folding reference includes the folding angle and crease; The closure type determination module is used to determine the closure type for closing a three-dimensional open structure, wherein the closure type includes any one of polygonal closure, surface closure, and hybrid closure of polygons and surfaces; The model generation module is used to perform a closing process on the three-dimensional open structure based on the closing type of the three-dimensional open structure, so as to obtain a three-dimensional solid model after the two-dimensional graphic is folded according to the folding reference.

11. An electronic device, characterized in that, include: Memory and processor; The memory is connected to the processor and is used to store programs; The processor is configured to implement the stereo model generation method as described in any one of claims 1 to 9 by running a program in the memory.

12. A computer program product, characterized in that, It includes computer program instructions that, when executed by a processor, cause the processor to implement the stereo model generation method as described in any one of claims 1 to 9.

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