Degenerated surface processing method and device of CAD model, equipment and medium

Abstract

The invention discloses a degenerated surface processing method and device of a CAD model, equipment and a medium, and relates to the technical field of computer aided design, and the method comprises the steps: importing and repairing an initial CAD model, building a watertight grid data structure, and obtaining a composite curved surface comprising a continuous curved surface and a discrete curved surface; carrying out degraded surface identification on the composite curved surface to obtain a corresponding degraded surface identification result; if the degenerated surface in the composite curved surface is a complete degenerated surface, deleting the complete degenerated surface, fusing adjacent edges of a target surface patch adjacent to the complete degenerated surface, and performing boundary topology reconstruction and discrete grid data stitching after reconstruction by using the fused curved surface information to obtain a degenerated surface processing result; and if the degeneration surface in the composite curved surface is a partial degeneration surface, cutting the area where the partial degeneration surface is located, converting the cut area into a complete degeneration surface, and executing the step of deleting the complete degeneration surface. Under the condition that original geometric data are not modified, a degenerated surface is automatically identified and processed.

Description

Technical Field

[0001] The present invention relates to the technical field of computer-aided design, and particularly relates to a method, device, equipment and medium for processing degenerate surfaces of a CAD model. Background Art

[0002] In a CAD (Computer-Aided Design) model, in different scenarios, such as during the modeling process, Boolean operations between entities, or the data conversion process of a CAD model between different software, some complex curved surfaces or thin shell structures may have degenerate surfaces. The existence of the degenerate surface problem will lead to a reduction in the geometric accuracy of the model. When performing precise dimensioning, measurement, or model-based engineering analysis (such as finite element analysis), these abnormal surfaces may lead to incorrect results. And the commonly used degenerate surface processing and repair require a large amount of manual interaction, with low efficiency and a high error rate. In addition, there are significant differences between the repaired model and the original geometric data and topological information of the input original model, which will change the true information of the original CAD model.

[0003] In summary, how to automatically identify and process degenerate surfaces without modifying the original geometric data is a technical problem to be solved in this field. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method, device, equipment and medium for processing degenerate surfaces of a CAD model, which can automatically identify and process degenerate surfaces without modifying the original geometric data. The specific solutions are as follows:

[0005] In the first aspect, the present application discloses a method for processing degenerate surfaces of a CAD model, including:

[0006] Import and repair the initial CAD model, and establish a watertight mesh data structure to obtain a composite surface including continuous surfaces and discrete surfaces;

[0007] Identify degenerate surfaces of the composite surface to obtain corresponding degenerate surface identification results;

[0008] If the degenerate surface in the composite surface is a completely degenerate surface, delete the completely degenerate surface, and fuse the adjacent edges of the target patches adjacent to the completely degenerate surface, so as to perform boundary topology reconstruction and stitching of the reconstructed discrete grid data using the fused surface information to obtain a degenerate surface processing result;

[0009] If the degenerate surface in the composite surface is a partially degenerate surface, perform a cutting process on the area where the partially degenerate surface is located, convert the cut area into a completely degenerate surface, and execute the step of deleting the completely degenerate surface.

[0010] Optionally, the identification of the degenerate surface for the composite surface to obtain the corresponding degenerate surface identification result includes:

[0011] Traverse the composite surface to obtain a patch identification table constructed based on the information of each patch;

[0012] Determine a patch as the current patch according to the patch identification order in the patch identification table, and determine the first area information of the current patch;

[0013] Determine the second area information of the target patch adjacent to the current patch;

[0014] Judge whether the current patch belongs to a completely degenerate surface according to the magnitude relationship between the area ratio of the first area information and the second area information and a preset area ratio threshold;

[0015] Determine the next patch as the new current patch according to the patch identification order, and jump to the step of determining the first area information of the current patch to obtain the degenerate surface identification result of whether each patch belongs to a completely degenerate surface.

[0016] Optionally, the identification of the degenerate surface for the composite surface to obtain the corresponding degenerate surface identification result includes:

[0017] Traverse all the boundary edges of each patch and determine the included angle value between the two boundary edges of each patch;

[0018] If the included angle value is less than a preset included angle tolerance, determine that the current patch is a partially degenerate surface; the partially degenerate surface includes normal boundary edges and candidate degenerate edges.

[0019] Optionally, the clipping process for the area where the partially degenerate surface is located includes:

[0020] Calculate the distance information between the corresponding points of the candidate degenerate edges of the same partially degenerate surface under the same parameters to determine the boundary edge spacing of the candidate degenerate edges;

[0021] If the boundary edge spacing is less than a preset margin tolerance, determine that the area between the candidate degenerate edges in the candidate degenerate surface is the area to be clipped, and perform a clipping process on the area to be clipped.

[0022] Optionally, the use of the fused surface information for boundary topology reconstruction and stitching of the discrete grid data after reconstruction to obtain the degenerate surface processing result includes:

[0023] Reconstruct the boundary topology relationship of the target patch according to the virtual super edges and super points obtained by fusion, and uniformly process the distribution information of each discrete point of the target adjacent edges in the reconstructed boundary topology relationship to obtain each target discrete point;

[0024] Align the target discrete points on the two target adjacent edges and merge the edges to obtain updated discrete grid data as the processing result of the degenerate surface.

[0025] Optionally, the reconstructing the boundary topological relationship of the target patch according to the virtual hyperedges and hyperpoints obtained by fusion includes:

[0026] Generate hyperpoints by using the virtual hyperedges obtained by fusion and the geometric data associated with the virtual hyperedges;

[0027] Reconstruct the boundary topological relationship of the target patch after deleting the completely degenerate surface by using the virtual hyperedges and the hyperpoints to obtain the reconstructed boundary topological relationship.

[0028] Optionally, the uniformly processing the distribution information of the discrete points on the target adjacent edges in the reconstructed boundary topological relationship to obtain each target discrete point includes:

[0029] Perform synchronous discretization processing on the discrete point distributions of the discrete points on the target adjacent edges in the reconstructed boundary topological relationship to refresh the current discrete points on the target adjacent edges to the same distribution, and use each of the current discrete points as each target discrete point on the target adjacent edges.

[0030] In a second aspect, the present application discloses a device for processing degenerate surfaces of a CAD model, including:

[0031] A structure building module, configured to import and repair an initial CAD model and build a watertight grid data structure to obtain a composite surface including a continuous surface and a discrete surface;

[0032] A degenerate surface recognition module, configured to recognize degenerate surfaces of the composite surface to obtain corresponding degenerate surface recognition results;

[0033] A first processing module, configured to, if the degenerate surface in the composite surface is a completely degenerate surface, delete the completely degenerate surface, and fuse the adjacent edges of the target patch adjacent to the completely degenerate surface, so as to perform boundary topology reconstruction and stitching of the reconstructed discrete grid data by using the fused surface information to obtain a degenerate surface processing result;

[0034] A second processing module, configured to, if the degenerate surface in the composite surface is a partially degenerate surface, perform a cropping process on the area where the partially degenerate surface is located, convert the cropped area into a completely degenerate surface, and execute the step of deleting the completely degenerate surface.

[0035] In a third aspect, the present application discloses an electronic device, including:

[0036] A memory, configured to store a computer program;

[0037] A processor for executing the computer program to implement the steps of the aforementioned CAD model degenerate surface processing method.

[0038] In a fourth aspect, the present application discloses a computer-readable storage medium for storing a computer program; wherein, when the computer program is executed by a processor, it implements the steps of the aforementioned CAD model degenerate surface processing method.

[0039] It can be seen that the present application discloses a method for processing degenerate surfaces of a CAD model, including: importing and repairing an initial CAD model, establishing a watertight mesh data structure to obtain a composite surface including continuous surfaces and discrete surfaces; performing degenerate surface recognition on the composite surface to obtain corresponding degenerate surface recognition results; if the degenerate surface in the composite surface is a completely degenerate surface, deleting the completely degenerate surface and fusing the adjacent edges of the target patches adjacent to the completely degenerate surface, so as to perform boundary topology reconstruction and stitching of the discrete mesh data after reconstruction using the information of the fused surface to obtain a degenerate surface processing result; if the degenerate surface in the composite surface is a partially degenerate surface, performing a cutting process on the area where the partially degenerate surface is located, converting the cut area into a completely degenerate surface, and executing the step of deleting the completely degenerate surface. Thus, by repairing the initial CAD model and establishing a watertight mesh data structure, a composite surface including continuous surfaces and discrete surfaces can be obtained. In this way, by further processing the composite surface, the processing of virtual surface information can be realized, and the processing of degenerate surfaces can be achieved without processing the original geometric information. Moreover, this solution identifies completely degenerate surfaces and partially degenerate surfaces, and then performs targeted processing on degenerate surfaces of different degenerate surface types, improving the quality of mesh generation, reducing the scale of mesh generation, and enhancing the accuracy and reliability of CAE analysis and calculation. Description of the Drawings

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the provided drawings.

[0041] Figure 1 It is a flowchart of a method for processing degenerate surfaces of a CAD model disclosed in the present application;

[0042] Figure 2 It is a schematic diagram of a completely degenerate surface disclosed in the present application;

[0043] Figure 3 It is a schematic diagram of virtual super-edge fusion disclosed in the present application;

[0044] Figure 4 Schematic diagram of the updated curved surface boundary disclosed in this application;

[0045] Figure 5 Schematic diagram of the process of updating and merging geometric data on the edge disclosed in this application;

[0046] Figure 6 Schematic diagram of the update operation of discrete grid data disclosed in this application;

[0047] Figure 7 Schematic diagram of a partially degenerate surface disclosed in this application;

[0048] Figure 8 Schematic diagram of the area to be trimmed of a partially degenerate surface disclosed in this application;

[0049] Figure 9 Schematic diagram of the edge segmentation of a partially degenerate surface disclosed in this application;

[0050] Figure 10 Schematic diagram of the trimming process of a partially degenerate surface disclosed in this application;

[0051] Figure 11 Schematic diagram of the process of forming a loop of a partially degenerate surface disclosed in this application;

[0052] Figure 12 Schematic diagram of the process of updating the surrounding adjacency relationship of a partially degenerate surface disclosed in this application;

[0053] Figure 13 Schematic diagram of the structure of a device for processing degenerate surfaces of a CAD model disclosed in this application;

[0054] Figure 14 Schematic diagram of the structure of an electronic device disclosed in this application. Detailed implementation manners

[0055] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0056] In a CAD model, the problem of degenerate faces often stems from the following scenarios: 1. During the actual modeling process, users may set inappropriate parameters during operations such as extrusion, rotation, lofting, etc. For example, when extruding a 2D profile, if the profile lines are not closed or there are self-intersections, degenerate faces may appear after extrusion. In the lofting operation, if the guide curves or cross-section profiles are not set properly, it is also easy to cause degenerate faces in the generated model. 2. Boolean operations between solids are also one of the common causes of degenerate faces. When performing union, difference, or intersection operations on two or more solids, if the geometric relationships between the solids are complex and the boundary conditions are not clear, some small faces that cannot be correctly processed may appear, thus forming degenerate faces. 3. When converting data of a CAD model between different software, due to differences in geometric kernels, data formats, and precisions of different software, it may lead to loss or deformation of the geometric information of the model. For example, when converting from one CAD software format (such as Pro / E file format) to another CAD software format (such as SolidWorks file format), degenerate faces may appear in some complex curved surfaces or thin-shell structures. When a CAD model is converted from a high-precision format to a low-precision format, in order to adapt to the new data structure and precision requirements, the geometric shape may be simplified, resulting in degenerate faces.

[0057] The existence of the problem of degenerate faces will lead to a reduction in the geometric precision of the model. When performing precise dimensioning, measurement, or model-based engineering analysis (such as finite element analysis), these abnormal faces may lead to incorrect results. For example, in finite element analysis, degenerate faces may affect the quality of mesh generation, resulting in inaccurate calculation of local stress and strain. In addition, if the CAD model is used for numerical control machining, degenerate faces may cause errors in tool path generation. In processes such as model manufacturing, these incorrect faces may affect the forming precision of the mold, thereby affecting the product quality.

[0058] Commonly used methods for dealing with degenerate faces include geometric repair, topological reconstruction, model simplification, or using various professional 3D modeling software for repair. For example, in SolidWorks, new solid geometries can be created by establishing lines and deleting faces for processing. Such operations for geometric repair of complex solid models may require a large amount of manual interaction, with low efficiency and a high error rate. In addition, there are significant differences between the repaired model and the original input model's geometric data and topological information, which may change the true information of the original CAD model.

[0059] Therefore, the present invention provides a solution for dealing with degenerate faces of a CAD model, which can automatically identify and process degenerate faces without modifying the original geometric data.

[0060] Refer to Figure 1As shown in the figure, an embodiment of the present invention discloses a method for processing degenerate surfaces of a CAD model, including:

[0061] Step S11: Import and repair the initial CAD model, and establish a watertight mesh data structure to obtain a composite surface including continuous surfaces and discrete surfaces.

[0062] In this embodiment, the surface gaps of the initial CAD model are processed to obtain a target CAD model without surface gaps. It can be understood that the initial CAD model generated according to the degenerate surface processing requirements has gaps. In order to obtain accurate degenerate surface processing results, it is necessary to repair the surface gaps of the initial CAD model with gaps to obtain a target CAD model without surface gaps. It should be noted that generating the initial CAD model based on the actual parameter information of the parts in the degenerate surface processing requirements is a conventional generation method, such as the reverse engineering method based on measurement data, the forward design method based on design parameters, and the hybrid design method combining the two. No specific limitation is made here. The degenerate surface processing requirements can specifically be the degenerate surface processing requirements of parts, where the parts can be mechanical parts in different fields, such as parts with complex surfaces like automotive body parts and aircraft hulls. No specific limitation is made here. For example: When the degenerate surface processing requirement is the degenerate surface processing requirement at the wing-body connection of an aircraft, all the wing parameters (airfoil data, planar shape, wing-body connection method), body parameters (section shape, connection area matching requirements), and connection area characteristic parameters at the wing-body connection of the aircraft are imported to generate the corresponding initial CAD model. The surface gaps of the initial CAD model at the wing-body connection of the aircraft are repaired to obtain a target CAD model without surface gaps at the wing-body connection of the aircraft.

[0063] Further, the target CAD model is subjected to mesh division and generation processing to obtain a composite surface that includes discrete surfaces and continuous surfaces. It can be understood that after the initial CAD model is repaired for gaps by the gap repair method and the target CAD model is obtained, the watertight mesh data structure of the target CAD model is further generated by the watertight mesh generation method. Among them, the watertight mesh generation framework is a tool or method for constructing the data structure of the target CAD model. In the processing of the target CAD model, the mesh is a discrete representation of the model surface. A watertight mesh means that the connections between the meshes are tight and gapless, just like being sealed. This characteristic is crucial for subsequent accurate calculations and analyses. Using this framework to establish the data structure can organize each part of the target CAD model in an orderly and standardized manner, facilitating various subsequent operations on the model. Specifically, after the data structure of the target CAD model is established through the watertight mesh generation framework, each obtained composite surface includes two parts: discrete surfaces and continuous surfaces. The discrete surface is obtained by discretizing the continuous surface and is composed of a series of discrete point, line, and surface elements. In subsequent degenerate surface processing, it is easier to perform operations on the discrete surface. The continuous surface is the part of the surface that maintains its original continuous characteristics and reflects the overall shape and geometric features of the surface. The discrete surface and the continuous surface cooperate with each other. The discrete surface provides a quantifiable basis for specific operations, and the continuous surface ensures the overall geometric properties of the surface, jointly constituting the composite surface and providing complete surface information for subsequent degenerate surface processing analysis and other operations. For example: for the target CAD model at the wing-body connection of an aircraft, its composite surface includes discrete surfaces and continuous surfaces. Among them, the continuous surfaces are: the theoretical shape of the wing (airfoil curve, twist surface), and the transition surface of the fuselage docking section. The discrete surfaces are the discretization of the continuous surface (such as the surface mesh required for CFD / structural analysis) and the supplementary mesh in the repaired gap area (such as the filling mesh at the wing-body connection).

[0064] Step S12: Identify the degenerate surfaces of the composite surface to obtain corresponding degenerate surface identification results.

[0065] In this embodiment, traverse the composite surface to obtain a patch recognition table constructed based on the information of each patch; determine a patch as the current patch according to the patch recognition order in the patch recognition table, and determine the first area information of the current patch; determine the second area information of the target patch adjacent to the current patch; judge whether the current patch belongs to a completely degenerate surface according to the magnitude relationship between the area ratio of the first area information and the second area information and a preset area ratio threshold; determine the next patch as the new current patch according to the patch recognition order, and jump to the step of determining the first area information of the current patch to obtain the recognition result of whether each patch belongs to a completely degenerate surface. It can be understood that by traversing the composite surface in the CAD model, checking its geometric and topological characteristics, and entering the judgment step of whether each patch is a completely degenerate surface, the specific judgment process is as follows: calculate the first area ( ) of the current patch and the second area ( ) of its adjacent surface. If the area ratio ( or ) exceeds the preset area ratio threshold (such as 1:100), it is determined as a completely degenerate surface; obtain the recognition results of completely degenerate surfaces for all patches according to the above steps. For example: for the target CAD model at the wing-fuselage connection of an aircraft, identify the area where degenerate surfaces are likely to appear in the composite surface of the wing connection. Specifically, detect small-area patches (such as area ratio <1:100) at the connection between the wing and the skin to obtain the recognition results of completely degenerate surfaces.

[0066] In this embodiment, traverse all the boundary edges of each patch and determine the included angle value between two boundary edges of each patch; if the included angle value is less than the preset angle tolerance, it is determined that the current patch is a partially degenerate surface; the partially degenerate surface includes normal boundary edges and candidate degenerate edges. It can be understood that for the corresponding patches identified as non-completely degenerate surfaces, a judgment step of whether they are partially degenerate surfaces is carried out. The specific judgment steps are as follows: traverse all the boundary edges of the current patch and calculate the included angle values between the boundary edges two by two; specifically, calculate the included angle value through the tangent vectors of the boundary edges (such as using the vector dot product formula). If the included angle value is less than the preset angle tolerance (such as 1°), it is determined that the current patch is a partially degenerate surface. For example: calculate the included angle of the boundary edges of the wing leading edge surface (such as included angle <1°). Output the corresponding marked completely degenerate surface (such as redundant skin surface) or partially degenerate surface (such as micro-gap at the joint).

[0067] Step S13: If the degenerate surface in the composite surface is a completely degenerate surface, delete the completely degenerate surface, and fuse the adjacent edges of the target patch adjacent to the completely degenerate surface, so as to perform boundary topology reconstruction and stitching of the discrete grid data after reconstruction using the fused surface information to obtain the degenerate surface processing result.

[0068] In this embodiment, if the surface is a completely degenerate surface, as follows Figure 2 shown, the surface is a completely degenerate surface. Among them, a degenerate surface refers to a geometrically incomplete patch (such as the vertices of a triangular face being collinear), which is generally caused by incorrect operation parameters of stretching, rotation, lofting in CAD modeling or geometric conflicts after Boolean operations. And a completely degenerate surface is a current patch that has a huge difference in area ratio with adjacent faces and is approximately an edge. When it is determined that the surface is a completely degenerate surface, first delete the surface . After deletion, the edge ac of the target patch and the edge bd of the target patch are free edges and also adjacent edges. In order to repair the topological relationship and maintain geometric consistency, they need to be reconnected to repair the topological relationship. Specifically, fuse the ac edge and the bd edge to obtain a virtual super edge. It should be noted that a virtual super edge is a virtual edge used to represent the fusion result of two adjacent edges. It does not directly modify the original geometric data, but merges two adjacent edges into a logical unit through a virtual topological relationship. The underlying data of the virtual super edge is based on bd or ac, that is, when generating the virtual super edge, select one of the edges (such as bd or ac) as the main edge of the underlying data. For example, if bd is selected as the main edge, the geometric data (such as node coordinates, parameterization information) of the virtual super edge is based on bd, and the data of the ac edge is mapped to bd. As Figure 3 shown, after deleting the completely degenerate surface, the two exposed edges are: edge ac: starting point a, ending point c. Edge bd: starting point b, ending point d. Operation process: fuse edge ac and edge bd to generate a virtual super edge. Assume that bd is selected as the main edge, then the geometric data of the virtual super edge is based on bd. The dotted line in the figure is the generated virtual super edge. For example: the treatment of the completely degenerate surface of the wing skin is to remove the redundant completely degenerate surface on the wing surface, and fuse the adjacent edges (such as edge ac and bd) exposed by the patch after deletion into a virtual super edge, and the underlying data is based on the main bearing edge (such as the wing main beam edge bd).

[0069] In this embodiment, reconstruct the boundary topological relationship of the target patch according to the virtual super edge and super point obtained by fusion, and uniformly process the distribution information of each discrete point of the target adjacent edge in the reconstructed boundary topological relationship to obtain each target discrete point; perform alignment processing and edge merging processing on the target discrete points of the two target adjacent edges to obtain the updated discrete grid data as the processing result of the degenerate surface.

[0070] Among them, reconstructing the boundary topological relationship of the target patch according to the virtual hyperedges and hyperpoints obtained by fusion includes: generating hyperpoints by using the virtual hyperedges obtained by fusion and the geometric data associated with the virtual hyperedges; using the virtual hyperedges and the hyperpoints to reconstruct the boundary topological relationship of the target patch after deleting the completely degenerate faces, so as to obtain the reconstructed boundary topological relationship. It can be understood that after generating the virtual hyperedges, two new hyperpoints are further generated. It should be noted that a hyperpoint is a virtual point used to represent the logical fusion of multiple geometric points. It does not directly modify the original geometric data, but combines multiple points into a logical unit through virtual topological relationships. Therefore, in this embodiment, one of the generated hyperpoints is associated with two points a and b, and the other hyperpoint is associated with two points c and d. Then, the boundary topological relationship of the target patch after deleting the completely degenerate faces is reconstructed by using the generated virtual hyperedges and hyperpoints. In this way, by generating virtual hyperedges and hyperpoints, the free edges (such as ac and bd) exposed after deleting the degenerate faces are repaired to ensure the integrity of the topological relationship of the model. In this way, the virtual hyperedges and hyperpoints do not modify the original geometric data, but achieve the fusion of edges and the association of points through virtual topological relationships, avoiding the loss or deformation of geometric information. Fusing two adjacent edges into a virtual hyperedge simplifies the topological structure of the model and facilitates subsequent processing. During the processing of the completely degenerate faces of the wing skin, the generation steps of hyperpoints are as follows: One hyperpoint is associated with the leading edge points a and b of the wing to ensure the continuity of the aerodynamic shape. Another hyperpoint is associated with the trailing edge points c and d of the wing to maintain topological symmetry.

[0071] As Figure 3 shown, the first hyperpoint: associates point a and point b, indicating their topological consistency. The second hyperpoint: associates point c and point d, indicating their topological consistency. The virtual hyperedge represents the fusion result of edge ac and edge bd, and the underlying data is mainly bd. The two hyperpoints are respectively associated with the starting points (a and b) and the ending points (c and d) to ensure the correctness of the topological relationship. Based on the above virtual hyperedges, hyperpoints, and the target patch after removing the completely degenerate faces, reconstruct the target patch and the target patch of the boundary topological relationship, update the boundary topological data of the two surfaces, as Figure 4 shown, the boundary of surface is updated to ef-fc-edge-be, and the boundary of surface is updated to edge-dh-hg-gb.

[0072] In this embodiment, the unified processing of the distribution information of the discrete points of the target adjacent edges in the reconstructed boundary topological relationship to obtain each target discrete point includes: performing synchronous discrete processing on the discrete point distribution of the discrete points of the target adjacent edges in the reconstructed boundary topological relationship to refresh the current discrete points of the target adjacent edges to the same distribution, and using each of the current discrete points as each target discrete point of the target adjacent edges. It can be understood that based on the reconstructed boundary topological relationship, the target adjacent edges on the updated surface are determined. To achieve seamless connection, it is necessary to ensure that the discrete grid nodes on these two edges have a consistent distribution. Therefore, synchronous discrete processing is performed on the discrete point distribution of the target adjacent edges to refresh the current discrete points of the two target adjacent edges to the same distribution, and the target discrete points are obtained. As follows Figure 5 Shown as follows: reparameterize the discrete points on the two target adjacent edges, adjust the number and spacing of the discrete points, so that the discrete point distributions (such as the number, position, density) of the two target adjacent edges are exactly the same. For example: if the target adjacent edge ac originally had 10 discrete points and the target adjacent edge bd originally had 8 discrete points, then through interpolation or deletion, both edges use the same number of target discrete points (such as: unified to 9), and ensure that the target discrete point spacing is distributed in the same proportion. Force-align the point coordinates of the adjusted target discrete points. For example, the th discrete point of the target adjacent edge ac corresponds exactly geometrically to the th discrete point of the target adjacent edge bd to avoid position deviation. This forced alignment process can be implemented based on the equal arc length segmentation or equal parameter segmentation algorithm of the parametric curve (such as B-spline). Then merge one target adjacent edge after forced alignment onto the other target adjacent edge to complete the merging process of the target discrete points, that is, complete the merging process of the discrete geometry on the edge. For the process of the node distribution of the discrete grid in the treatment of the completely degenerate surface of the wing skin: refresh the discrete points on the virtual super edge (such as the wing leading edge nodes) to the same density to ensure the uniformity of the aerodynamic grid.

[0073] Furthermore, after completing the merging of the discrete geometry on the edge, perform a connection operation on the discrete geometry on the two surfaces, as follows Figure 6 Shown as follows, first fuse the corresponding boundary points of the two surfaces; then take one surface as the first surface, use the boundary grid on the first surface as the benchmark, take the other surface as the second surface, insert corresponding grid points in the discrete grid on the second surface and perform edge splitting operations; then use the boundary grid on the second surface as the benchmark, insert corresponding grid points in the discrete grid on the first surface and perform edge splitting operations; finally, perform a stitching operation on the corresponding grid points of the first surface and the second surface to complete the update operation of the discrete grid data. Thus, the deletion operation of the completely degenerate surface is completed, the modification of the surrounding topological relationship is completed, and at the same time, the update of the discrete geometry on the virtual surface is completed.

[0074] Step S14: If the degenerate surface in the composite surface is a partially degenerate surface, then the area where the partially degenerate surface is located is trimmed, and the trimmed area is converted into a completely degenerate surface, and the step of deleting the completely degenerate surface is executed.

[0075] In this embodiment, as Figure 7 shown, Figure 7 is a schematic diagram of a partially degenerate surface. Among them, a partially degenerate surface refers to a surface where the distance between some internal boundaries is extremely small, but the overall area is not much different from the surrounding surfaces. The trimming process of the area where the partially degenerate surface is located includes: calculating the distance information between the corresponding points of the candidate degenerate edges of the same partially degenerate surface under the same parameters to determine the boundary edge spacing of the candidate degenerate edges; if the boundary edge spacing is less than the preset edge margin tolerance, it is determined that the area between the candidate degenerate edges in the candidate degenerate surface is the area to be trimmed, and the area to be trimmed is trimmed. It can be understood that the area to be trimmed is first determined. Specifically, the boundary edges corresponding to the included angle values less than the preset included angle tolerance are found from each boundary edge in the partially degenerate surface as candidate degenerate edges, and the distance between two candidate degenerate edges is calculated. The method for calculating the distance between two edges is as follows: Calculate the distance between the discrete point pairs under the same parameter u between two candidate degenerate edges. u is 0 for the head end of the edge, 1 for the tail end of the edge, 0.5 for the midpoint of the edge, and so on. The average distance between these distances is used as the boundary edge spacing between two candidate degenerate edges. Among them, the calculation formula for the boundary edge spacing of the candidate degenerate edges is as follows:

[0076] ;

[0077] Among them, represents the distance between the discrete point pairs on the th candidate degenerate edge, represents the number of discrete point pairs.

[0078] If the boundary edge spacing between two edges in a certain surface is less than the specified preset edge margin tolerance, then the area to be trimmed is the area enclosed by these two edges. As Figure 8 shown, when the discrete point pair distance between the two candidate degenerate edges calculated based on the discrete point pairs and the candidate degenerate edge is and the calculated boundary edge spacing is less than the specified preset edge margin tolerance, then the area enclosed by the two candidate degenerate edges and the candidate degenerate edge is the area to be trimmed.

[0079] Furthermore, as Figure 9 shown, judge the candidate degenerate edge Whether the length gap with the candidate degenerate edge is too large. Specifically, take the length difference between the candidate degenerate edge and the candidate degenerate edge as the target length. If the target length is greater than the preset length threshold, it is determined that the length gap between the two is too large, and the long side needs to be segmented so that the length of the long side after cropping is almost the same as that of the short side. At this time, after cropping is updated to be connected to and has the same length as . Then, two boundary edges ( and the cropped ) are removed from the current surface, and then the remaining edges are combined into a loop. Specifically, as shown in Figure 10 , after deleting edge ef and edge fg, the remaining edges de, edge gh, edge ha, edge ab, edge bd, and edge de are combined into a loop. Among them, a new superpoint object m is generated during the process of combining into a loop to fuse endpoint e and endpoint g. In this way, edge de and edge gh will share an endpoint m, as shown in Figure 11 .

[0080] After cropping part of the degenerate surface, update the surrounding topological relationships, specifically as shown in Figure 12 . After cropping the part of the degenerate surface , the cropped surface is the completely degenerate surface. Then, it will be processed and the adjacency relationships of the surrounding surfaces will be updated in accordance with the processing method of the aforementioned completely degenerate surface. After the processing of the above steps, the topological relationships between the virtual surfaces are updated to maintain the correctness of the model topological relationships. At the same time, the discrete grids on the virtual surfaces are also updated correspondingly, so that the discrete grids on the processed virtual surfaces are also connected seamlessly to each other.

[0081] It can be seen that the present application discloses a method for processing degenerate surfaces of a CAD model, including: importing and repairing an initial CAD model, establishing a watertight mesh data structure to obtain a composite surface containing continuous surfaces and discrete surfaces; identifying degenerate surfaces of the composite surface to obtain corresponding degenerate surface identification results; if the degenerate surface in the composite surface is a completely degenerate surface, deleting the completely degenerate surface and fusing the adjacent edges of the target patches adjacent to the completely degenerate surface, so as to perform boundary topology reconstruction and stitching of the discrete mesh data after reconstruction using the surface information after fusion to obtain a degenerate surface processing result; if the degenerate surface in the composite surface is a partially degenerate surface, performing a cutting process on the area where the partially degenerate surface is located, converting the cut area into a completely degenerate surface, and executing the step of deleting the completely degenerate surface. Thus, by repairing the initial CAD model and establishing a watertight mesh data structure, a composite surface containing continuous surfaces and discrete surfaces can be obtained. In this way, by further processing the composite surface, the processing of virtual surface information can be realized, and the processing of degenerate surfaces can be realized without processing the original geometric information. Moreover, this solution identifies completely degenerate surfaces and partially degenerate surfaces, and then performs targeted processing on degenerate surfaces of different degenerate surface types, improving the quality of mesh generation, reducing the scale of mesh generation, and enhancing the accuracy and reliability of CAE analysis and calculation.

[0082] Referring Figure 13 as shown, the present invention also correspondingly discloses a device for processing degenerate surfaces of a CAD model, including:

[0083] A structure establishment module 11, configured to import and repair an initial CAD model, establish a watertight mesh data structure to obtain a composite surface containing continuous surfaces and discrete surfaces;

[0084] A degenerate surface identification module 12, configured to identify degenerate surfaces of the composite surface to obtain corresponding degenerate surface identification results;

[0085] A first processing module 13, configured to, if the degenerate surface in the composite surface is a completely degenerate surface, delete the completely degenerate surface and fuse the adjacent edges of the target patches adjacent to the completely degenerate surface, so as to perform boundary topology reconstruction and stitching of the discrete mesh data after reconstruction using the surface information after fusion to obtain a degenerate surface processing result;

[0086] A second processing module 14, configured to, if the degenerate surface in the composite surface is a partially degenerate surface, perform a cutting process on the area where the partially degenerate surface is located, convert the cut area into a completely degenerate surface, and execute the step of deleting the completely degenerate surface.

[0087] It can be seen that the present application discloses importing and repairing an initial CAD model, establishing a watertight mesh data structure to obtain a composite surface including continuous surfaces and discrete surfaces; identifying degenerate surfaces for the composite surface to obtain corresponding degenerate surface identification results; if the degenerate surface in the composite surface is a completely degenerate surface, deleting the completely degenerate surface and fusing the adjacent edges of the target patches adjacent to the completely degenerate surface, so as to perform boundary topology reconstruction and stitching of the discrete mesh data after reconstruction using the information of the fused surface to obtain a degenerate surface processing result; if the degenerate surface in the composite surface is a partially degenerate surface, performing a cropping process on the area where the partially degenerate surface is located and converting the cropped area into a completely degenerate surface, and executing the step of deleting the completely degenerate surface. Thus, by repairing the initial CAD model and establishing a watertight mesh data structure, a composite surface including continuous surfaces and discrete surfaces can be obtained. In this way, by further processing the composite surface, the processing of virtual surface information can be realized, and the processing of degenerate surfaces can be realized without processing the original geometric information. Moreover, this solution identifies completely degenerate surfaces and partially degenerate surfaces, and then performs targeted processing on degenerate surfaces of different degenerate surface types, improving the quality of mesh generation, reducing the scale of mesh generation, and enhancing the accuracy and reliability of CAE analysis and calculation.

[0088] Furthermore, the embodiment of the present application also discloses an electronic device, Figure 14 which is a structural diagram of an electronic device 20 shown according to an exemplary embodiment, and the content in the figure should not be considered as any limitation on the scope of use of the present application.

[0089] Figure 14 It is a structural schematic diagram of an electronic device 20 provided by an embodiment of the present application. The electronic device 20 may specifically include: at least one processor 21, at least one memory 22, a power supply 23, a communication interface 24, an input / output interface 25, and a communication bus 26. Among them, the memory 22 is used to store a computer program, and the computer program is loaded and executed by the processor 21 to implement the relevant steps in the degenerate surface processing method of the CAD model disclosed in any of the foregoing embodiments. In addition, the electronic device 20 in this embodiment may specifically be an electronic computer.

[0090] In this embodiment, the power supply 23 is used to provide working voltage for each hardware device on the electronic device 20; the communication interface 24 can create a data transmission channel between the electronic device 20 and external devices, and the communication protocol it follows is any communication protocol applicable to the technical solution of the present application, and specific limitations are not imposed on it here; the input / output interface 25 is used to obtain external input data or output data to the outside, and its specific interface type can be selected according to specific application needs, and no specific limitations are made here.

[0091] Among them, the processor 21 may include one or more processing cores, such as a 4-core processor, an 8-core processor, etc. The processor 21 may be implemented in at least one hardware form of DSP (Digital Signal Processing), FPGA (Field-Programmable Gate Array), or PLA (Programmable Logic Array). The processor 21 may also include a main processor and a coprocessor. The main processor is a processor used to process data in the wake state, also known as the CPU (Central Processing Unit); the coprocessor is a low-power processor used to process data in the standby state. In some embodiments, the processor 21 may be integrated with a GPU (Graphics Processing Unit), and the GPU is responsible for the rendering and drawing of the content to be displayed on the display screen. In some embodiments, the processor 21 may further include an AI (Artificial Intelligence) processor, and the AI processor is used to process computational operations related to machine learning.

[0092] In addition, the memory 22, as a carrier for resource storage, may be a read-only memory, a random access memory, a disk, or an optical disc, etc. The resources stored thereon may include an operating system 221, a computer program 222, etc., and the storage method may be temporary storage or permanent storage.

[0093] Among them, the operating system 221 is used to manage and control each hardware device and the computer program 222 on the electronic device 20, so as to realize the operation and processing of the massive data 223 in the memory 22 by the processor 21. It may be Windows Server, Netware, Unix, Linux, etc. In addition to the computer program capable of implementing the degraded surface processing method of the CAD model executed by the electronic device 20 disclosed in any of the foregoing embodiments, the computer program 222 may further include a computer program capable of completing other specific tasks. The data 223 may include not only the data transmitted by external devices received by the electronic device, but also the data collected by its own input / output interface 25, etc.

[0094] Furthermore, the present application also discloses a computer-readable storage medium for storing a computer program; wherein, when the computer program is executed by a processor, it implements the foregoing disclosed degraded surface processing method of the CAD model. For the specific steps of this method, reference may be made to the corresponding content disclosed in the foregoing embodiments, and details will not be repeated here.

[0095] In this specification, the various embodiments are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple. For the relevant parts, reference can be made to the description in the method section.

[0096] Those skilled in the art can further realize that the units and algorithm steps of each example described in combination with the embodiments disclosed in this article can be implemented by electronic hardware, computer software, or a combination of the two. To clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described according to functions in the above description. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Skilled professionals can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of this application. The steps of the methods or algorithms described in combination with the embodiments disclosed in this article can be directly implemented by hardware, software modules executed by a processor, or a combination of the two. The software modules can be placed in a random access memory (RAM), internal memory, read-only memory (ROM), electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disks, removable disks, CD-ROM (Compact Disc-Read Only Memory), or any other form of storage medium known in the technical field.

[0097] Finally, it should also be noted that in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including", or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article, or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or elements inherent to such process, method, article, or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of additional identical elements in the process, method, article, or device including the said element.

[0098] The above has introduced the solution provided by the present invention in detail. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A method for processing a degenerate surface of a CAD model, characterized in that: include: Import and repair the initial CAD model, and establish a watertight mesh data structure to obtain a composite surface containing continuous and discrete surfaces; Performing degenerate surface identification on the composite surface to obtain a corresponding degenerate surface identification result; If the degenerate surface in the composite surface is a completely degenerate surface, the completely degenerate surface is deleted, and the adjacent edges of the target surface patches adjacent to the completely degenerate surface are fused, so as to use the fused surface information to reconstruct the boundary topology and stitch the reconstructed discrete grid data to obtain the degenerate surface processing result; If the degenerate surface in the composite surface is a partially degenerate surface, the area where the partially degenerate surface is located is clipped, and the clipped area is converted into a fully degenerate surface, and the step of deleting the fully degenerate surface is performed.

2. The method for processing a degenerate surface of a CAD model according to claim 1, characterized in that: The performing degenerate surface identification on the composite surface to obtain a corresponding degenerate surface identification result includes: Traversing the composite surface to obtain a patch identification table constructed based on information of each patch; Determine a patch as a current patch according to the patch identification order in the patch identification table, and determine first area information of the current patch; Determine second area information of a target patch adjacent to the current patch; Determining whether the current face patch is a completely degenerate face according to a relationship between an area ratio of the first area information to the second area information and a preset area ratio threshold; The next patch is determined as a new current patch according to the patch identification sequence, and the process jumps to the step of determining the first area information of the current patch to obtain a degenerate surface identification result of whether each patch is a completely degenerate surface.

3. The method for processing a degenerate surface of a CAD model according to claim 1, characterized in that: The performing degenerate surface identification on the composite surface to obtain a corresponding degenerate surface identification result includes: Traverse all the boundary edges of each face patch and determine the angle between the two boundary edges of each face patch; If the angle value is less than a preset angle tolerance, the current face is determined to be a partially degenerate face; the partially degenerate face includes a normal boundary edge and a candidate degenerate edge.

4. The method for processing degenerate surfaces of a CAD model according to claim 3, characterized in that: The clipping of the area where the partial degenerate surface is located includes: Calculating distance information between corresponding points of the candidate degenerate edges of the same portion of the degenerate surface under the same parameters to determine the boundary edge spacing of the candidate degenerate edges; If the boundary edge spacing is less than the preset edge tolerance, the region between the candidate degenerate edges in the candidate degenerate surface is determined to be a to-be-cropped region, and the to-be-cropped region is cropped.

5. The method for processing degenerate surfaces of a CAD model according to claim 1, characterized in that: The method of using the fused surface information to reconstruct the boundary topology and stitching the reconstructed discrete grid data to obtain the degenerate surface processing result includes: Reconstructing the boundary topological relationship of the target face according to the fused virtual hyperedges and hyperpoints, and uniformly processing the distribution information of each discrete point of the target adjacent edge in the reconstructed boundary topological relationship to obtain each target discrete point; The target discrete points of two target adjacent edges are aligned and edge merged to obtain updated discrete grid data as a degenerate surface processing result.

6. The method for processing degenerate surfaces of a CAD model according to claim 5, characterized in that: The step of reconstructing the boundary topological relationship of the target facet according to the fused virtual hyperedges and superpoints includes: Generate a super point using the fused virtual hyperedge and geometric data associated with the virtual hyperedge; The boundary topological relationship of the target face after deleting the completely degenerate face is reconstructed by using the virtual hyperedge and the superpoint to obtain a reconstructed boundary topological relationship.

7. The method for processing degenerate surfaces of a CAD model according to claim 5, characterized in that: The distribution information of each discrete point of the target adjacent edge in the reconstructed boundary topological relationship is uniformly processed to obtain each target discrete point, including: The discrete point distribution of each discrete point of the target adjacent edge in the reconstructed boundary topological relationship is synchronously discretized to refresh the current discrete points of the target adjacent edge to the same distribution, and use each current discrete point as each target discrete point of the target adjacent edge.

8. A degenerate surface processing device for a CAD model, characterized in that: include: The structure building module is used to import and repair the initial CAD model and build a watertight grid data structure to obtain a composite surface including continuous surfaces and discrete surfaces; A degenerate surface identification module, used for performing degenerate surface identification on the composite surface to obtain a corresponding degenerate surface identification result; The first processing module is used for deleting the completely degenerate surface if the degenerate surface in the composite surface is a completely degenerate surface, and fusing the adjacent edges of the target surface patch adjacent to the completely degenerate surface, so as to reconstruct the boundary topology by using the fused surface information and sew the reconstructed discrete mesh data to obtain the degenerate surface processing result; The second processing module is used to, if the degenerate surface in the composite surface is a partially degenerate surface, clip the area where the partially degenerate surface is located, convert the clipped area into a fully degenerate surface, and execute the step of deleting the fully degenerate surface.

9. An electronic device, characterized in that: include: Memory, used to store computer programs; A processor is used to execute the computer program to implement the steps of the degenerate surface processing method of a CAD model as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: Used to store a computer program; wherein, when the computer program is executed by a processor, the steps of the degenerate surface processing method of a CAD model as described in any one of claims 1 to 7 are implemented.

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