Complex grid cutting method and device based on autonomous cutting algorithm

Abstract

The invention provides a complex grid cutting method based on an autonomous cutting algorithm. The complex grid cutting method comprises the following steps: preprocessing a cutting grid and a to-be-cut grid body; performing collision detection on the preprocessed cutting grid and the grid body to be cut; carrying out intersection calculation on the intersected triangles based on a detection result to obtain an intersection line; respectively embedding the obtained intersecting lines into the cutting grid and the grid body to be cut; carrying out topological separation on the to-be-cut grid body based on intersecting lines, and marking a part located in the positive direction of the cut grid as a first sub-grid; topological separation is carried out on the cutting network based on intersecting lines, and the part located in the to-be-cut grid body is marked as a second sub-grid; and sewing the first sub-grid and the second sub-grid to serve as a final cut sub-grid body. The method solves the problem of low success rate of Boolean operation of complex grids.

Description

Technical Field

[0001] The present invention relates to the technical field of engineering digital modeling, and in particular to a complex grid cutting method and device based on an autonomous shearing algorithm. Background Art

[0002] Mesh models are an important method for representing three-dimensional shapes, with triangular meshes being the most widely used. Mesh models can represent arbitrarily complex surfaces and spatial shapes with arbitrary precision. In a mesh model, the number of edges per face may vary. When each face in a mesh model is composed entirely of triangles, it is called a triangular mesh. Non-triangular meshes can be converted to triangular meshes by triangulating each convex polygonal face in the mesh model.

[0003] In 3D geological modeling research, geological models often use boundary representation methods to represent geological interfaces or entities. Geological interfaces are generally composed of a single geometric surface, while geological entities are composed of multiple geometric surfaces. Surface clipping is unavoidable during the modeling process, and surface clipping algorithms have become key to achieving 3D geological modeling and model analysis. Surface clipping algorithms have been a hot topic in fields such as computer graphics and computer-aided design. They can generally be divided into two categories based on the type of surface being clipped: parametric surface clipping, which is widely used in engineering design due to its excellent mathematical properties and ease of control and editing, such as NURBS and subdivision surfaces. Polygonal surface clipping, on the other hand, typically involves polygonalization based on a set of collected discrete points. However, since the surface is approximated using discrete irregular polygons, clipping on these surfaces is complex. This method is suitable for 3D visualization and analytical computations in engineering, such as triangulated irregular networks and finite element meshes.

[0004] In the field of three-dimensional geology, due to the infinite complexity of geological interfaces, they are not suitable for expression using parametric surfaces. Therefore, geological models are mostly expressed using polygonal surfaces, among which irregular triangulated networks are the most widely used. Therefore, the study of clipping algorithms for irregular triangulated networks is particularly important.

[0005] According to the type of clipping elements, the clipping of irregular triangulated networks can be divided into: face / face clipping and line / face clipping. Compared with the mature face / face clipping algorithm, the complexity of spatial curves makes it impossible to implement arbitrary curve clipping surface algorithms, resulting in the immaturity of the line / face clipping algorithm of irregular triangulated networks. It mainly uses computer interaction to generate reasonable clipping lines to clip the model surface. There are a large number of clipping problems of geological curves and geological surfaces in geological modeling. In this regard, the existing technology uses the idea of ​​constrained edge embedding in Delaunay triangulation to embed contour lines into the face mesh and then perform clipping, but it has special requirements for contour lines, and the mesh will be deformed after clipping.

[0006] In addition, when processing complex meshes (especially polygonal meshes with a large number of vertices), the success rate of mesh Boolean cutting operations will drop significantly. This is mainly reflected in three aspects: first, mesh models (compared to traditional NURBS surfaces or solids) are more prone to non-manifold geometry, holes, self-overlap, and inconsistent normals, which increase the difficulty of Boolean operations; second, conventional algorithms have insufficient fault tolerance for edge cases such as coplanarity and tangent contact, and are prone to failure when processing complex meshes; especially when the number of mesh vertices is large, the precision errors of floating-point calculations will accumulate, causing key judgment errors (such as misjudging the intersection state of faces) or generating extremely small invalid geometric fragments during cutting, ultimately leading to operation failure. Summary of the Invention

[0007] Based on the above background, the present invention provides a complex mesh cutting method based on an autonomous shearing algorithm to solve the problem of low success rate of Boolean operations on complex meshes. The specific technical solution adopted is as follows: A first aspect of the present invention provides a complex mesh cutting method based on an autonomous shearing algorithm, comprising the following steps: Preprocess the cutting mesh and the mesh body to be cut; Perform collision detection on the pre-processed cutting mesh and the mesh to be cut; Perform intersection calculation on intersecting triangles based on the detection results to obtain the intersection line; The obtained intersection lines are embedded into the cutting mesh and the mesh to be cut respectively; Perform topological separation on the mesh to be cut based on the intersection line, and record the part in the positive direction of the cut mesh as the first sub-mesh; The cutting network is topologically separated based on the intersection line, and the part inside the grid to be cut is recorded as the second subgrid; The first sub-grid and the second sub-grid are stitched together to form the final cut sub-grid body.

[0008] Furthermore, the pre-processing of the cut mesh and the mesh body to be cut includes at least triangulation, removal of duplicate vertices and / or repair of non-manifold geometry.

[0009] Furthermore, the collision detection between the pre-processed cutting grid and the grid body to be cut includes: Calculate whether the bounding boxes of any triangle in the cut mesh and any triangle in the mesh to be cut overlap one by one; If the two triangles overlap, the next step of intersection calculation is performed. If they do not overlap, no intersection calculation is performed.

[0010] Furthermore, the intersection operation of the intersecting triangles based on the detection results to obtain the intersection line includes: Intersect the three sides of the first triangle with the second triangle respectively, and then intersect the three sides of the second triangle with the first triangle respectively to obtain the intersection point set; If there is only one intersection point in the intersection point set, it is determined that there is no intersection line segment; If there are only two intersection points in the intersection point set and the two intersection points do not overlap, then the line connecting the two intersection points is determined to be an intersection line segment; If there are more than two intersection points in the intersection point set, the duplicate intersection points are removed. If there are only two intersection points after removing the duplicate intersection points, the line connecting the two intersection points is determined to be an intersection line segment. If there are still more than two intersection points after removing the duplicate intersection points, it is determined that there is no intersection line segment. All the obtained intersection line segments are deduplicated, and the remaining intersection line segments after deduplication are connected end to end to form an intersection line.

[0011] Furthermore, embedding the obtained intersection lines into the cutting grid and the grid body to be cut includes: Determine one by one which triangle face of the mesh to be cut is located at the intersection point on the intersection line; Perform constrained Delaunay triangulation on the triangles containing the intersection points one by one using valid triangles as units, where the valid triangles contain the intersection point and intersection line segment constraints; Determine whether all intersection line segments on the intersection line have been embedded. If not, embed the unembedded intersection line segments into the grid to be cut until all intersection line segments have been embedded.

[0012] Furthermore, the topological separation of the mesh to be cut based on the intersection line includes: Using the intersection line as the boundary, the mesh to be cut is divided into two or more sub-triangulated meshes; The sub-triangulation set located in the positive direction of the cutting mesh is taken as the result of Boolean intersection, and the sub-triangulation set located in the negative direction of the cutting mesh is taken as the result of Boolean subtraction; The sub-triangulated mesh set obtained by Boolean intersection is reconstructed into a triangulated mesh as the first sub-mesh.

[0013] Furthermore, stitching the first sub-grid and the second sub-grid includes: Using the first sub-mesh as the stitched object, all mesh nodes and triangles in the second sub-mesh are added to the first sub-mesh. Remove duplicate mesh nodes after addition and adjust the normal direction of all triangles to be uniformly from inside to outside; The final cut sub-mesh is reconstructed based on the deduplicated mesh nodes and the adjusted normal triangles.

[0014] A second aspect of the present invention provides a computer device comprising a memory and a processor, wherein the memory stores computer instructions, and the processor executes the complex grid cutting method as described in the first aspect above by executing the computer instructions.

[0015] A third aspect of the present invention provides a computer-readable storage medium storing computer instructions. When the computer instructions are executed by a computer, the complex grid cutting method as described in the first aspect is executed.

[0016] The beneficial effects of the present invention are as follows: The present invention's complex mesh cutting method, based on an autonomous shearing algorithm, significantly improves the success rate and stability of Boolean operations on complex meshes through innovative preprocessing, collision detection, intersection calculation, intersection embedding, bidirectional topological separation, and sub-mesh stitching processes, effectively overcoming the industry's core pain point of low success rates for Boolean operations on complex meshes. The present invention significantly reduces designers' rework and manual repair time, improves work efficiency and model quality, and provides reliable basic tool support for three-dimensional digital design. It has significant engineering practical value and broad prospects for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a simplified flowchart of an embodiment of the complex grid cutting method of the present invention.

[0018] Figure 2 Schematic diagram of the relationship between two triangles in space.

[0019] Figure 3 Schematic diagram of dividing a mesh body to be cut into multiple sub-triangulated meshes according to an embodiment of the present invention.

[0020] Figure 4 The figure is a schematic diagram showing an example of cutting a terrain grid using the method of the present invention. DETAILED DESCRIPTION

[0021] Embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0022] See also Figure 1 The first embodiment of the present invention provides a complex mesh cutting method based on an autonomous shearing algorithm, comprising the following steps: S1. Preprocess the cut mesh and the mesh body to be cut.

[0023] As a preferred embodiment, in this embodiment, preprocessing the cut mesh and the mesh body to be cut includes at least triangulation, removal of duplicate vertices and / or repairing non-manifold geometry.

[0024] S2. Perform collision detection on the pre-processed cutting mesh and the mesh body to be cut.

[0025] The purpose of collision detection is to quickly determine which triangles in the cutting mesh intersect with the mesh to be cut. It does not need to accurately calculate the coordinate position of the intersection point. Its purpose is to reduce the complexity of subsequent calculations.

[0026] See also Figure 2 , the relationship between two triangles in space is usually one of four cases: 1) Intersection, such as Figure 2 As shown in (a), the common part is a straight line segment; at this time, the planes where the two triangles are located intersect.

[0027] 2) Overlap, the common part is one area, such as Figure 2 As shown in (b), the two triangles are coplanar at this time.

[0028] 3) Separate, no common parts, such as Figure 2 As shown in (c) in the figure, the two triangles may be separated regardless of whether the planes they are located in are intersecting, parallel or overlapping.

[0029] 4) Collision: The two triangles are in a critical state of contact, including the common point and common boundary states, such as Figure 2 As shown in (d) in the figure; it can also be seen as a singular state of intersection or overlap.

[0030] As a preferred implementation scheme, in this embodiment, collision detection adopts the following scheme: Calculate whether the bounding boxes of any triangle in the cut mesh and any triangle in the mesh to be cut overlap one by one; If the two triangles overlap, the next step of intersection calculation is performed. If they do not overlap, no intersection calculation is performed.

[0031] S3. Perform intersection calculation on the intersecting triangles based on the detection results to obtain the intersection line.

[0032] The precise intersection of intersecting triangles is reflected on a single primitive, which is to calculate the intersection position information of the triangles.

[0033] As a preferred implementation scheme, in this embodiment, the following scheme is used to perform the intersection operation to obtain the intersection line: Intersect the three sides of the first triangle with the second triangle respectively, and then intersect the three sides of the second triangle with the first triangle respectively to obtain the intersection point set; If there is only one intersection point in the intersection point set, it is determined that there is no intersection line segment; If there are only two intersection points in the intersection point set and the two intersection points do not overlap, then the line connecting the two intersection points is determined to be an intersection segment; If there are more than two intersection points in the intersection point set, the duplicate intersection points are removed. If there are only two intersection points after removing the duplicate intersection points, the line connecting the two intersection points is determined to be an intersection line segment; if there are still more than two intersection points after removing the duplicate intersection points, it is determined that there is no intersection line segment; All the obtained intersection line segments are deduplicated, and the remaining intersection line segments after deduplication are connected end to end to form an intersection line.

[0034] S4. Embed the obtained intersection lines into the cutting grid and the grid body to be cut respectively.

[0035] Intersection line embedding is the prerequisite for topological separation, which is to interpolate the nodes in the intersection line (that is, the endpoints of the intersection line segments that constitute the intersection line) into the triangulation network, and reconstruct the triangulation network using the intersection line as a constraint.

[0036] As a preferred implementation scheme, in this embodiment, the intersection line embedding adopts the following scheme: Determine one by one which triangle face of the mesh to be cut is located at the intersection point on the intersection line; Perform constrained Delaunay triangulation on the triangles containing the intersection points one by one using valid triangles as units, where the valid triangles contain the intersection point and intersection line segment constraints; Determine whether all intersection line segments on the intersection line have been embedded. If not, embed the unembedded intersection line segments into the grid to be cut until all intersection line segments have been embedded.

[0037] For the mesh A to be cut and the intersection line C, a specific implementation example of the above process is: First, obtain the indices of all nodes and triangles in the mesh A to be cut, as well as all intersections in the intersection line C, and store the sequence numbers of the intersection segments where the intersection points are located; Then, traverse the intersection points in the intersection line C to determine whether the intersection point is a newly added node, and record the triangle index where the intersection point is located in the mesh A to be cut and the vertex number where the intersection point is embedded in the mesh A to be cut; Next, the intersection line C is divided into valid triangles based on the triangle index where the intersection point is located. This way, the intersection line is embedded in the valid triangles of the mesh A to be cut (a valid triangle is a triangle that has the newly added intersection point and intersection line segment passing through it). Then, based on the intersection points and intersection segments within the valid triangles, constrained Delaunay triangulation, i.e., mesh subdivision, is performed on the valid triangles one by one; Finally, a check is performed to see if there are any intersecting line segments embedded in the mesh body A to be cut. If so, constraint adjustments are made to the mesh in the mesh body A to be cut until all intersecting line segments participate in the network construction in the mesh body A to be cut.

[0038] In this embodiment, the specific implementation of constrained Delaunay triangulation includes: First, insert the nodes in the intersection line into the triangle one by one, and ensure that the inserted nodes meet the planar Delaunay condition, that is, whether the newly added nodes are within the circumcircle of the triangle space is used to determine whether the triangle is a minimum cavity triangle; Secondly, determine whether the constrained intersection line segment participates in the triangle network. If not, it is necessary to use the intersection line segment as the boundary to divide it into left and right sub-cavities and re-construct the network.

[0039] S5. Topologically separate the mesh to be cut based on the intersection line, and record the part located in the positive direction of the cut mesh as the first sub-mesh.

[0040] As a preferred implementation scheme, in this embodiment, topological separation adopts the following scheme: First, the mesh to be cut is divided into two or more sub-triangulated meshes based on the intersection line, such as Figure 3 The specific implementation is as follows: starting from the first triangle, using the edge of the triangle as the boundary, topologically search for triangles in the remaining triangles that share the same edge with the boundary, and then use the boundary edge formed by the triangles that share the same edge as the starting point for the next judgment. If an intersection line segment is encountered, the edge is not used as the boundary for topological calculation until all triangles are divided into sub-triangulation networks.

[0041] Then the sub-triangulation set located in the positive direction of the cutting mesh is taken as the result of Boolean intersection, and the sub-triangulation set located in the negative direction of the cutting mesh is taken as the result of Boolean subtraction, such as Figure 3 Part I and Part II are the sub-triangulation sets for Boolean intersection; Finally, the sub-triangulated mesh set obtained by Boolean intersection is reconstructed, that is, the vertex indexes are renumbered in sequence from 1, 2, 3, ..., and the triangles in the sub-triangulated mesh set are renumbered according to the new vertex indexes, thereby finally generating an independent sub-triangulated mesh as the first sub-mesh.

[0042] S6. Perform topological separation on the cutting network based on the intersection line, and record the part located inside the grid body to be cut as the second sub-grid.

[0043] The specific method of topological separation can be referred to the content in step S5, which will not be described in detail here.

[0044] S7. Stitch the first sub-grid and the second sub-grid together to form the final cut sub-grid body.

[0045] As a preferred embodiment, in this embodiment, the suturing operation adopts the following scheme: Using the first sub-mesh as the stitched object, all mesh nodes and triangles in the second sub-mesh are added to the first sub-mesh. Remove duplicate mesh nodes after addition and adjust the normal direction of all triangles to be uniformly from inside to outside; The final cut sub-mesh is reconstructed based on the deduplicated mesh nodes and the adjusted normal triangles.

[0046] The following is an example of cutting a terrain grid using the method of the present invention.

[0047] See also Figure 4 In this example, the grid to be cut is a terrain solid grid model constructed by vertically stretching downward to a depth of 467.649 meters based on the terrain surface data with an average grid spacing of 4 meters in the horizontal direction. The cutting grid is a stratum interface grid with an average grid spacing of 20 meters in the horizontal direction, such as Figure 4 (a) and Figure 4 As shown in (b), the original cut mesh, the wireframe mode of the mesh to be cut, and the smooth mode are respectively displayed.

[0048] The upper surface of the terrain grid (i.e. the original terrain surface) is geometrically fitted with the stratum interface grid to form a "thin sheet" spatial relationship. This feature theoretically generates multiple nearly parallel complex intersection lines when finding the intersection. This dense, micro-scale intersection structure greatly increases the difficulty of the intersection algorithm. In this example, a total of 3 intersection lines are generated, one of which is the main intersection line on the periphery, and the other two are internal intersection lines generated by the stratum interface grid partially exceeding the original terrain surface. Through the autonomous shearing algorithm steps of the present invention, the topological segmentation of the complex terrain grid can be finally achieved, and the volume of the sheared sub-grid is 2184876.051m³. As Figure 4 (c) and Figure 4 (d) in the figure shows the wireframe mode and smooth mode of the clipped sub-mesh.

[0049] Another embodiment of the present invention further provides a computer device, including a memory and a processor, wherein the memory stores computer instructions, and the processor executes the complex grid cutting method disclosed in the above embodiment by executing the computer instructions.

[0050] Another embodiment of the present invention further provides a computer-readable storage medium, which stores computer instructions. When the computer instructions are executed by a computer, the complex grid cutting method disclosed in the above embodiment is executed.

[0051] It should be noted that the method of the embodiment of the present invention can be performed by a single device, such as a computer or server. The method of this embodiment can also be applied in a distributed scenario, where multiple devices cooperate to perform the method. In such a distributed scenario, one of the multiple devices may only perform one or more steps of the method of the embodiment of the present invention, and the multiple devices will interact with each other to complete the method.

[0052] It should be noted that the above description is limited to some embodiments of the present invention. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims may be performed in an order different from that described in the above embodiments and still achieve the desired results. Furthermore, the processes depicted in the accompanying drawings do not necessarily require the specific order or sequential order shown to achieve the desired results. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0053] The embodiments of the present invention are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the scope of protection of the present invention.

Claims

1. A complex mesh cutting method based on an autonomous shearing algorithm, characterized in that: The steps include: Preprocess the cutting mesh and the mesh body to be cut; Perform collision detection on the pre-processed cutting mesh and the mesh to be cut; Perform intersection calculation on intersecting triangles based on the detection results to obtain the intersection line; The obtained intersection lines are embedded into the cutting mesh and the mesh to be cut respectively; Perform topological separation on the mesh to be cut based on the intersection line, and record the part in the positive direction of the cut mesh as the first sub-mesh; The cutting network is topologically separated based on the intersection line, and the part inside the grid to be cut is recorded as the second subgrid; The first sub-grid and the second sub-grid are stitched together to form the final cut sub-grid body.

2. The complex grid cutting method based on the autonomous shearing algorithm according to claim 1, characterized in that: The pre-processing of the cutting mesh and the mesh body to be cut includes at least triangulation, removal of duplicate vertices and / or repairing of non-manifold geometry.

3. The complex grid cutting method based on the autonomous shearing algorithm according to claim 2, characterized in that: The collision detection between the pre-processed cutting grid and the grid body to be cut includes: Calculate whether the bounding boxes of any triangle in the cut mesh and any triangle in the mesh to be cut overlap one by one; If the two triangles overlap, the next step of intersection calculation is performed. If they do not overlap, no intersection calculation is performed.

4. The complex grid cutting method based on the autonomous shearing algorithm according to claim 3, characterized in that: The intersection operation of the intersecting triangles based on the detection results to obtain the intersection line includes: Intersect the three sides of the first triangle with the second triangle respectively, and then intersect the three sides of the second triangle with the first triangle respectively to obtain the intersection point set; If there is only one intersection point in the intersection point set, it is determined that there is no intersection line segment; If there are only two intersection points in the intersection point set and the two intersection points do not overlap, then the line connecting the two intersection points is determined to be an intersection line segment; If there are more than two intersection points in the intersection point set, the duplicate intersection points are removed. If there are only two intersection points after removing the duplicate intersection points, the line connecting the two intersection points is determined to be an intersection line segment. If there are still more than two intersection points after removing the duplicate intersection points, it is determined that there is no intersection line segment. All the obtained intersection line segments are deduplicated, and the remaining intersection line segments after deduplication are connected end to end to form an intersection line.

5. The complex grid cutting method based on the autonomous shearing algorithm according to claim 4, characterized in that: The step of embedding the obtained intersection lines into the cutting grid and the grid body to be cut includes: Determine one by one which triangle face of the mesh to be cut is located at the intersection point on the intersection line; Perform constrained Delaunay triangulation on the triangles containing the intersection points one by one using valid triangles as units, where the valid triangles contain the intersection point and intersection line segment constraints; Determine whether all intersection line segments on the intersection line have been embedded. If not, embed the unembedded intersection line segments into the grid to be cut until all intersection line segments have been embedded.

6. The complex grid cutting method based on the autonomous shearing algorithm according to claim 5, characterized in that: The topological separation of the mesh to be cut based on the intersection line includes: Using the intersection line as the boundary, the mesh to be cut is divided into two or more sub-triangulated meshes; The sub-triangulation set located in the positive direction of the cutting mesh is taken as the result of Boolean intersection, and the sub-triangulation set located in the negative direction of the cutting mesh is taken as the result of Boolean subtraction; The sub-triangulated mesh set obtained by Boolean intersection is reconstructed into a triangulated mesh as the first sub-mesh.

7. The complex grid cutting method based on the autonomous shearing algorithm according to claim 6, characterized in that: The stitching of the first sub-grid and the second sub-grid comprises: Using the first sub-mesh as the stitched object, all mesh nodes and triangles in the second sub-mesh are added to the first sub-mesh. Remove duplicate mesh nodes after addition and adjust the normal direction of all triangles to be uniformly from inside to outside; The final cut sub-mesh is reconstructed based on the deduplicated mesh nodes and the adjusted normal triangles.

8. A computer device, characterized in that: The method comprises a memory and a processor, wherein the memory stores computer instructions, and the processor executes the complex grid cutting method according to any one of claims 1 to 7 by executing the computer instructions.

9. A computer-readable storage medium, characterized in that The storage medium stores computer instructions, and when the computer instructions are executed by a computer, the complex grid cutting method according to any one of claims 1 to 7 is executed.

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