Three-dimensional model hole feature recognition method and device based on B-Rep topology
By using a B-Rep topology-based method, in-plane and boundary holes in 3D models are identified, solving the problem of the inability to identify boundary holes in existing technologies. This achieves efficient hole feature recognition and is suitable for high-precision manufacturing.
Patent Information
- Application Number
- CN202511223559.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-29
- Publication Date
- 2025-12-23
AI Technical Summary
Existing feature search methods based on B-Rep topology only support searching for holes within a surface and cannot search for boundary holes composed of the boundaries of multiple surfaces, thus limiting their applicability.
The inner ring is obtained by traversing the outer surface of the 3D model, the concavity and convexity of the edges are detected, the concavity and convexity of the side surfaces are determined by the ray method, and the path search is performed in combination with geometric feature constraints to identify non-rounded edges and rounded edge holes.
It enables the identification of in-plane and boundary holes in 3D models, saving computing resources and costs, making it suitable for high-precision manufacturing scenarios and improving processing accuracy.
Smart Images
Figure CN121190509A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of computer-aided manufacturing technology, and in particular to a method, apparatus, equipment, and computer program product for identifying hole features in a three-dimensional model based on B-Rep topology. Background Technology
[0002] In the field of Computer Aided Manufacturing (CAM), the identification of hole features in 3D models is crucial for the roughing and finishing stages of CNC machining. In the roughing stage, redundant material needs to be removed quickly. If hole features on the part surface are not accurately identified and avoided, it will lead to increased tool idle travel, increased risk of tool breakage, and uneven distribution of machining allowance. In the finishing stage, unidentified and unrepaired microholes can easily cause tool chatter and overcutting.
[0003] Existing 3D model hole feature recognition technologies are mainly divided into three categories: (1) Feature search method based on B-Rep topology: This type of method searches by parsing the B-Rep boundary representation data structure of the CAD model, that is, the hierarchical topological relationship of faces, edges and loops, combined with the geometric features of holes.
[0004] (2) Feature search method based on attribute adjacency graph (AAG): Attribute adjacency graphs represent the topological and geometric relationships of CAD models through graph structures. The core idea of this type of method is to abstract the geometric faces of the model into graph nodes, the adjacency relationships between faces into edges, and describe the geometric semantics of faces and adjacency relationships through additional attributes (such as curvature, normal, area, etc.). In the hole recognition scenario, AAG locates regions with hole features by analyzing the topological connectivity and attribute distribution patterns of the graph.
[0005] (3) Feature recognition method based on neural network: This type of method learns the implicit feature expression of CAD model through data-driven learning. Its core idea is to model hole recognition as a classification or segmentation task, and use deep network to automatically extract the geometric and topological features of holes from input data (such as voxels, point clouds, meshes or B-Rep structures). Through end-to-end training, it captures the statistical distribution law of holes.
[0006] However, in practical applications, feature search methods based on attribute adjacency graphs require traversing all faces and adjacency relationships to construct a full AAG model, resulting in high computational complexity and poor process adaptability. Neural network-based feature recognition methods require large amounts of labeled data, leading to high manual costs. They also exhibit significant errors in hole scenarios not covered by the training set, and the voxel / point cloud representation causes the loss of precise geometric information in boundary representations, making them unsuitable for high-precision manufacturing scenarios. Existing B-Rep topology-based feature search methods only support searching for intra-face holes and cannot search for boundary holes composed of multiple face boundaries, thus limiting their applicability. Summary of the Invention
[0007] Therefore, the technical problem to be solved by the present invention is to overcome the problem that the feature search method based on B-Rep topology in the prior art only supports searching for in-plane holes and cannot search for boundary holes composed of the boundaries of multiple planes.
[0008] To address the aforementioned technical problems, this invention provides a method for identifying hole features in 3D models based on B-Rep topology, comprising: Search for in-plane holes, including: Traverse each outer surface of the 3D model to obtain the inner loop located on the outer surface of the 3D model, which is denoted as the in-plane closed wireframe. Perform edge concavity / convexity detection on the inner closed wireframe; If the edge of an in-plane closed frame is a convex edge, then the in-plane closed frame is an in-plane hole; If the edges of the closed frame in the plane are rounded, the concavity or convexity of the side surface of the closed frame in the plane can be determined by the ray method; if the side surface of the closed frame in the plane is concave, then the closed frame in the plane is an in-plane hole. Search for holes with non-rounded corners, including: Starting from any point on the outer ring of the outer surface of the 3D model, a path search is performed using non-rounded edge constraints, adjacent outer surface constraints of non-rounded edges, and side surface constraints of non-rounded edges until the path forms a loop, thus obtaining the first boundary closed wireframe. If the first boundary closed frame satisfies the circumduction detection constraint, the angle constraint of the non-rounded corner hole, the normal constraint, and the side loop constraint, then the first boundary closed frame is a non-rounded corner hole. Search for rounded corner holes, including: Starting from any point on the outer ring of the outer surface of the 3D model, a path search is performed using rounded edge constraints, tangency constraints, curvature constraints, and angular constraints of the adjacent outer surfaces of the rounded edge until the path forms a loop, thus obtaining the second boundary closed wireframe. If the second boundary closed frame satisfies the directional detection constraint, then the second boundary closed frame is a rounded corner hole.
[0009] Preferably, the method of determining the concavity / convexity of the side surface of the closed wireframe within the plane using ray casting includes: Select the first sampling point on the edge of the closed bounding box in the plane; The first sampling point is moved a preset distance along the normal of the outer surface of the edge to obtain the second sampling point; Starting from the second sampling point, draw a ray towards the side of the edge; Detect whether the ray intersects with the side surface; if an intersection exists, the side surface is convex; if no intersection exists, the side surface is concave.
[0010] Preferably, the non-rounded corner edge constraint is: the included angle between two adjacent faces of the edge containing the search point is not 0; The constraint on the adjacent outer surfaces of non-rounded edges is: the angle between the outer surface of the edge where the search point is located and the outer surface of the adjacent edge to be searched is less than a first preset angle; The side constraint for non-rounded edges is: the angle between the outer surface of the edge containing the search point and the side surface is greater than the second preset angle.
[0011] Preferably, the orientation detection constraint is as follows: according to the right-hand rule, the axial direction of the boundary closed frame is calculated based on the orientation of the boundary closed frame, and the axial direction of the boundary closed frame is greater than 90° with the normal of the outer surface of the boundary closed frame.
[0012] Preferably, the angular constraint of the non-rounded corner hole is: and ; The normal constraint is: and ; The side loop constraint is: the sides of the first boundary closed loop form a closed loop; in, Let be the normal vector of the closed loop of the first boundary. Let be the normal vector of the outer surface of the first boundary closed wireframe. Let be the normal vector of the side of the closed bounding box. As the first constraint angle, For the second constraint angle, This is an operation to find the angle between two vectors.
[0013] Preferably, the rounded corner constraint is: the included angle between two adjacent faces of the edge containing the search point is 0; The tangency constraint is: the edge containing the search point is tangent to the adjacent edge to be searched or the included angle is the smallest; The curvature constraint is: the curvature of the outer surface of the edge containing the search point is less than the curvature of the side surface of that edge; The angular constraint of the adjacent outer surfaces of the rounded edge is: the outer surface of the edge where the search point is located is tangent to the outer surface of the adjacent edge to be searched or the included angle is less than the third preset angle.
[0014] Preferably, during the path search process, the searched points of the current path are saved to the history list of searched points, and a search point not in the history list is selected as the next search point for the current path.
[0015] The present invention also provides a device for identifying hole features in a three-dimensional model based on B-Rep topology, comprising: An in-plane hole identification module, used to search for in-plane holes, includes: The closed wireframe acquisition unit is used to traverse each outer surface of the 3D model and acquire the inner loop located on the outer surface of the 3D model, which is denoted as the in-plane closed wireframe. The concavity / convexity detection unit is used to perform concavity / convexity detection on the edges of an in-plane closed frame. If the edge of the in-plane closed frame is a convex edge, then the in-plane closed frame is an in-plane hole. If the edge of the in-plane closed frame is a rounded edge, then the concavity / convexity of the side surface of the in-plane closed frame is determined by the ray method. If the side surface of the in-plane closed frame is a concave surface, then the in-plane closed frame is an in-plane hole. A non-rounded corner hole recognition module is used to search for holes with non-rounded corners, including: The non-rounded corner hole path search unit is used to search for a path starting from any point on the outer ring of the outer surface of the 3D model, using non-rounded corner constraints, adjacent outer surface constraints of non-rounded corners, and side constraints of non-rounded corners, until the path forms a loop and the first boundary closed wireframe is obtained. The non-rounded corner hole constraint detection unit is used to determine if the first boundary closed frame is a non-rounded corner hole if it satisfies the circumferential detection constraint, the angle constraint, the normal constraint, and the side loop constraint. A rounded corner hole recognition module is used to search for rounded corner holes, including: The rounded edge hole path search unit is used to search for a path starting from any point on the outer ring of the outer surface of the 3D model, using rounded edge constraints, tangency constraints, curvature constraints and angular constraints of the outer surfaces adjacent to the rounded edge, until the path forms a loop and the second boundary closed wireframe is obtained. A rounded corner hole constraint detection unit is used to determine if a second boundary closed frame is a rounded corner hole if it satisfies the circumduction detection constraint.
[0016] This invention also provides a device for identifying hole features in a 3D model based on B-Rep topology, comprising: The memory is used to store computer programs; the processor is used to execute the computer programs to implement the steps of the above-described method for identifying hole features in a three-dimensional model based on B-Rep topology.
[0017] The present invention also provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the above-described method for identifying hole features in a three-dimensional model based on B-Rep topology.
[0018] Compared with the prior art, the above-described technical solution of the present invention has the following advantages: This invention discloses a method for identifying holes in 3D models based on B-Rep topology. First, the inner ring of the outer surface of the 3D model is obtained. Based on the geometric features of in-plane holes, the concavity / convexity of the edges is detected. Closed frames with convex edges are identified as in-plane holes. For rounded edges, ray casting is further performed to identify closed frames with concave sides as in-plane holes. Next, the outer ring of the outer surface of the 3D model is obtained. From any starting point, a path search is performed using the geometric features of the boundary holes to obtain closed frames. These closed frames are then checked again to ensure they satisfy the geometric features of the boundary holes, thus identifying both non-rounded and rounded edge holes. This invention directly identifies in-plane and boundary holes in 3D models based on B-Rep topology, saving computational resources and costs. It has strong process adaptability, is suitable for high-precision manufacturing scenarios, and facilitates implementation in practical applications, improving processing accuracy. Attached Figure Description
[0019] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein: Figure 1 This is a schematic diagram of the holes in the 3D model; Figure 2 Here is an example diagram of an in-plane hole; Figure 3 Here is an example diagram of a boundary hole; Figure 4 Here is an example diagram of a rounded corner hole; Figure 5 This is a flowchart of a method for identifying hole features in a 3D model based on B-Rep topology, according to the present invention. Figure 6 This is a flowchart for identifying in-plane holes; Figure 7 This is a flowchart for identifying boundary holes; Figure 8 This is a schematic diagram of the angle between adjacent faces; Figure 9 This is a schematic diagram of a hole recognition result according to an embodiment of the present invention; Explanation of the markings in the accompanying drawings: 1. Outer surface; 2. Side; 3. Closed frame. Detailed Implementation
[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.
[0021] The proposed 3D model hole feature recognition method and its key algorithms are both based on the B-Rep model. The B-Rep model contains both geometric and topological information about the geometric elements in the corresponding geometric entity of the part. Typical geometric information can be divided into three categories: points, curves, and surfaces, which are the geometric elements constituting the surface of the entity and used to describe its geometric characteristics. Typical topological information includes vertex, edge, loop, face, shell, and solid, used to describe the connection relationships between geometric elements. There is a correspondence between topology and geometry: nodes correspond to points, edges to curves, and faces to surfaces. The topological information of different B-Rep models has a clear correlation. An edge is the boundary between adjacent faces. An edge adjacent to two faces is the common edge of those two faces. A common edge corresponds to a pair of directed edges with opposite directions, belonging to the two adjacent faces of this common edge, called the edges of the faces. The direction of the directed edge is the same as or opposite to the direction of the curve corresponding to the corresponding common edge.
[0022] Reference Figure 1 As shown, the hole features of the CAD 3D model consist of three parts: the closed wireframe, the outer surface, and the side surface.
[0023] This invention first divides the holes in a 3D model into in-plane holes and boundary holes. (Refer to...) Figure 2 As shown, the closed frame of the in-plane hole lies within an outer surface. (Refer to...) Figure 3 As shown, the closed frame of the boundary hole is composed of multiple outer surfaces joined together. Furthermore, this invention further subdivides the boundary hole into non-rounded corner holes and rounded corner holes, wherein the closed frame of the rounded corner holes is rounded at the corners, as shown... Figure 4 As shown.
[0024] Reference Figure 5 As shown, this invention provides a method for identifying hole features in a 3D model based on B-Rep topology, including: S1: Search for holes within the surface; S2: Search for holes with non-rounded corners; S3: Search for holes with rounded corners.
[0025] Reference Figure 6 As shown, the search for in-plane holes in S1 includes: S11: Traverse each outer surface of the 3D model and obtain all closed wireframes located on the outer surfaces of the 3D model.
[0026] S12: Detect the closed wireframe obtained in S11 and perform inner and outer loop detection: If the closed wireframe is the outer loop of the outer surface, discard it; if the closed wireframe is the inner loop of the outer surface, record it as an in-plane closed wireframe, and then execute S13.
[0027] S13: Perform concavity / convexity detection on the edges of the in-face closed wireframe, classifying the edges of the in-face closed wireframe into concave edges, convex edges, and rounded edges.
[0028] Specifically, if the included angle between two adjacent faces of an edge is less than 180°, then the edge is a convex edge; if the included angle between two adjacent faces of an edge is greater than 180°, then the edge is a concave edge. For example, if the angle between the outer surface and the side surface of a slotted hole is less than 180°, it is a convex edge and needs to be retained; if the angle between the side surface and the bottom surface of a slotted hole is greater than 180°, it is a concave edge and needs to be discarded.
[0029] S14: If the edge of the closed frame in the face is a convex edge, then the closed frame in the face is an in-face hole; if the edge of the closed frame in the face is a concave edge, then discard it; if the edge of the closed frame in the face is a rounded edge, then execute S15.
[0030] S15: Use the ray method to determine the concavity or convexity of the side surface of the closed frame in the plane; if the side surface of the closed frame in the plane is concave, then the closed frame in the plane is an in-plane hole; if the side surface of the closed frame in the plane is convex, then discard it.
[0031] Specifically, the convexity / concavity of the side surfaces of the closed wireframe within the plane is determined using the ray method, including: Select the first sampling point on the edge of the closed bounding box in the plane; The first sampling point is moved a preset distance along the normal of the outer surface of the edge to obtain the second sampling point; Starting from the second sampling point, draw a ray towards the side of the edge; the length of the ray is the distance from the second sampling point to the centroid of the closed frame in the plane. Detect whether the ray intersects with the side surface; if an intersection exists, the side surface is convex; if no intersection exists, the side surface is concave.
[0032] Before searching for boundary holes, their geometric constraints need to be set. These constraints are used both during path searching and closed wireframe matching. During the search, the geometric constraints determine which adjacent edge to select or the outer and side surfaces of an edge. The boundary hole search process is described below. Figure 7 As shown, it includes the following steps: Input the starting point and get the current search point, edges, outer surface, side surface, and a historical list of searched points; The search begins from the starting point, and the process checks whether the current search point is in the history list of searched points. If it is, the search is terminated. Determine whether the searched edges form a closed wireframe; If a closed wireframe is formed, determine whether the closed wireframe satisfies the geometric feature constraints of the boundary hole; if yes, output the identified boundary hole; otherwise, end the current search. If a closed wireframe is not formed, select the next search point and the adjacent edge of the edge containing the current search point based on the geometric constraints of the boundary hole, and determine the outer surface and side surface, then continue the search.
[0033] During the path search process, the searched points of the current path are saved to the history list of searched points, and a search point not in the history list is selected as the next search point for the current path to prevent the path search from continuing along the already searched edges.
[0034] In this embodiment, before path search, the outer ring edge of the outer surface of the 3D model is selected as the starting edge, and the two adjacent faces of the starting edge are selected as the outer surface and the side surface, respectively. During the path search, the adjacent edge of the current edge is selected as the next edge to be searched, and the new outer surface and side surface are determined. If a closed wireframe is found, the geometric feature constraints of the closed wireframe and the boundary hole are matched.
[0035] This invention classifies boundary holes into non-rounded corner holes and rounded corner holes. When identifying non-rounded corner holes, their geometric constraint features are used. When identifying rounded corner holes, their geometric constraint features are used.
[0036] Specifically, the geometric constraint features of non-rounded corner holes include non-rounded corner constraints, adjacent outer surface constraints of non-rounded corners, side constraints of non-rounded corners, circumferential detection constraints, angular constraints, normal constraints, and side loop constraints of non-rounded corner holes.
[0037] In S2, the steps for searching for holes with non-rounded corners include: S21: Starting from any point on the outer ring of the outer surface of the 3D model, perform path search using non-rounded edge constraints, adjacent outer surface constraints of non-rounded edges, and side surface constraints of non-rounded edges until the path forms a loop, thus obtaining the first boundary closed wireframe. S22: If the first boundary closed frame satisfies the circumduction detection constraint, the angle constraint of the non-rounded corner hole, the normal constraint, and the side loop constraint, then the first boundary closed frame is a non-rounded corner hole.
[0038] Specifically, the non-rounded corner constraint is: the included angle between two adjacent faces of the edge containing the search point is not 0. See the diagram for an illustration of the included angle between adjacent faces. Figure 8 As shown.
[0039] The constraint on the adjacent outer surfaces of non-rounded edges is: the angle between the outer surface of the edge where the search point is located and the outer surface of the adjacent edge to be searched is less than a first preset angle.
[0040] The side constraint for non-rounded edges is: the angle between the outer surface of the edge containing the search point and the side surface is greater than the second preset angle.
[0041] The orientation detection constraint is as follows: according to the right-hand rule, the axial direction of the boundary closed frame is calculated based on the orientation of the boundary closed frame, and the axial direction of the boundary closed frame is greater than 90° with the normal of the outer surface of the boundary closed frame.
[0042] The angular constraint for non-rounded corner holes is: and ;in, Let be the normal vector of the closed loop of the first boundary. Let be the normal vector of the outer surface of the first boundary closed wireframe. Let be the normal vector of the side of the closed bounding box. As the first constraint angle, For the second constraint angle, This is an operation to find the angle between two vectors.
[0043] The normal constraint is: and .
[0044] The side loop constraint is: the sides of the first boundary closed wireframe form a closed loop.
[0045] Specifically, the geometric constraint features of rounded corner holes include rounded corner constraints, tangency constraints, curvature constraints, angular constraints of adjacent outer surfaces of the rounded corner, and circumduction detection constraints.
[0046] In S3, the steps for searching for rounded corner holes include: S31: Starting from any point on the outer ring of the outer surface of the 3D model, perform path search using rounded edge constraints, tangency constraints, curvature constraints and angular constraints of the adjacent outer surfaces of the rounded edge until the path forms a loop, and obtain the second boundary closed wireframe. S32: If the second boundary closed frame satisfies the circumduction detection constraint, then the second boundary closed frame is a rounded corner hole.
[0047] Specifically, the rounded edge constraint is: the included angle between two adjacent faces of the edge containing the search point is 0.
[0048] The tangency constraint is: the edge containing the search point is tangent to the adjacent edge to be searched or the included angle is the smallest, and the closer to tangency, the smaller the included angle.
[0049] Since the outer surface of a rounded hole is flatter than its side surface, the curvature constraint is: the curvature of the outer surface of the edge containing the search point is less than the curvature of the side surface of that edge.
[0050] The angular constraint of the adjacent outer surfaces of the rounded edge is: the outer surface of the edge where the search point is located is tangent to the outer surface of the adjacent edge to be searched or the included angle is less than the third preset angle.
[0051] This invention can select to identify holes in the input faces, edges, and volumes. Figure 9 This is a schematic diagram of a hole identification result according to an embodiment of the present invention.
[0052] In summary, the B-Rep topology-based method for identifying holes in 3D models described in this invention first obtains the inner ring of the outer surface of the 3D model. Based on the geometric features of in-plane holes, the concavity / convexity of the edges is detected, identifying closed frames with convex edges as in-plane holes. Further ray casting is performed on rounded edges to identify closed frames with concave sides as in-plane holes. Next, the outer ring of the outer surface of the 3D model is obtained, and a path search is performed from any starting point using the geometric constraints of boundary holes to obtain closed frames. These closed frames are then checked again to ensure they satisfy the geometric constraints of boundary holes, thus identifying both non-rounded and rounded edge holes. This invention directly uses B-Rep topology to identify in-plane and boundary holes in 3D models, saving computational resources and costs. It has strong process adaptability, is suitable for high-precision manufacturing scenarios, and facilitates implementation in practical applications, improving processing accuracy.
[0053] Based on the above-mentioned method for identifying hole features in a 3D model based on B-Rep topology, this invention also provides a device for identifying hole features in a 3D model based on B-Rep topology, comprising: An in-plane hole identification module, used to search for in-plane holes, includes: The closed wireframe acquisition unit is used to traverse each outer surface of the 3D model and acquire the inner loop located on the outer surface of the 3D model, which is denoted as the in-plane closed wireframe. The concavity / convexity detection unit is used to perform concavity / convexity detection on the edges of an in-plane closed frame. If the edge of the in-plane closed frame is a convex edge, then the in-plane closed frame is an in-plane hole. If the edge of the in-plane closed frame is a rounded edge, then the concavity / convexity of the side surface of the in-plane closed frame is determined by the ray method. If the side surface of the in-plane closed frame is a concave surface, then the in-plane closed frame is an in-plane hole. A non-rounded corner hole recognition module is used to search for holes with non-rounded corners, including: The non-rounded corner hole path search unit is used to search for a path starting from any point on the outer ring of the outer surface of the 3D model, using non-rounded corner constraints, adjacent outer surface constraints of non-rounded corners, and side constraints of non-rounded corners, until the path forms a loop and the first boundary closed wireframe is obtained. The non-rounded corner hole constraint detection unit is used to determine if the first boundary closed frame is a non-rounded corner hole if it satisfies the circumferential detection constraint, the angle constraint, the normal constraint, and the side loop constraint. A rounded corner hole recognition module is used to search for rounded corner holes, including: The rounded edge hole path search unit is used to search for a path starting from any point on the outer ring of the outer surface of the 3D model, using rounded edge constraints, tangency constraints, curvature constraints and angular constraints of the outer surfaces adjacent to the rounded edge, until the path forms a loop and the second boundary closed wireframe is obtained. A rounded corner hole constraint detection unit is used to determine if a second boundary closed frame is a rounded corner hole if it satisfies the circumduction detection constraint.
[0054] This invention also provides a device for identifying hole features in a 3D model based on B-Rep topology, comprising: The memory is used to store computer programs; the processor is used to execute the computer programs to implement the steps of the above-described method for identifying hole features in a three-dimensional model based on B-Rep topology.
[0055] The present invention also provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the above-described method for identifying hole features in a three-dimensional model based on B-Rep topology.
[0056] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.
[0057] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.
[0058] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.
[0059] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.
[0060] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
Claims
1. A method for identifying hole features in a 3D model based on B-Rep topology, characterized in that, include: Search for in-plane holes, including: Traverse each outer surface of the 3D model to obtain the inner loop located on the outer surface of the 3D model, which is denoted as the in-plane closed wireframe. Perform edge concavity / convexity detection on the inner closed wireframe; If the edge of an in-plane closed frame is a convex edge, then the in-plane closed frame is an in-plane hole; If the edges of the closed frame in the plane are rounded, the concavity or convexity of the side surface of the closed frame in the plane can be determined by the ray method; if the side surface of the closed frame in the plane is concave, then the closed frame in the plane is an in-plane hole. Search for holes with non-rounded corners, including: Starting from any point on the outer ring of the outer surface of the 3D model, a path search is performed using non-rounded edge constraints, adjacent outer surface constraints of non-rounded edges, and side surface constraints of non-rounded edges until the path forms a loop, thus obtaining the first boundary closed wireframe. If the first boundary closed frame satisfies the circumduction detection constraint, the angle constraint of the non-rounded corner hole, the normal constraint, and the side loop constraint, then the first boundary closed frame is a non-rounded corner hole. Search for rounded corner holes, including: Starting from any point on the outer ring of the outer surface of the 3D model, a path search is performed using rounded edge constraints, tangency constraints, curvature constraints, and angular constraints of the adjacent outer surfaces of the rounded edge until the path forms a loop, thus obtaining the second boundary closed wireframe. If the second boundary closed frame satisfies the directional detection constraint, then the second boundary closed frame is a rounded corner hole.
2. The method for identifying hole features in a 3D model based on B-Rep topology according to claim 1, characterized in that, The method of using rays to determine the concavity or convexity of the sides of a closed wireframe within a plane includes: Select the first sampling point on the edge of the closed bounding box in the plane; The first sampling point is moved a preset distance along the normal of the outer surface of the edge to obtain the second sampling point; Starting from the second sampling point, draw a ray towards the side of the edge; Detect whether the ray intersects with the side surface; if an intersection exists, the side surface is convex; if no intersection exists, the side surface is concave.
3. The method for identifying hole features in a 3D model based on B-Rep topology according to claim 1, characterized in that, The constraint for non-rounded edges is: the included angle between two adjacent faces of the edge containing the search point is not 0; The constraint on the adjacent outer surfaces of non-rounded edges is: the angle between the outer surface of the edge where the search point is located and the outer surface of the adjacent edge to be searched is less than a first preset angle; The side constraint for non-rounded edges is: the angle between the outer surface of the edge containing the search point and the side surface is greater than the second preset angle.
4. The method for identifying hole features in a 3D model based on B-Rep topology according to claim 1, characterized in that, The orientation detection constraint is as follows: according to the right-hand rule, the axial direction of the boundary closed frame is calculated based on the orientation of the boundary closed frame, and the axial direction of the boundary closed frame is greater than 90° with the normal of the outer surface of the boundary closed frame.
5. The method for identifying hole features in a 3D model based on B-Rep topology according to claim 1, characterized in that, The angular constraint for non-rounded corner holes is: and ; The normal constraint is: and ; The side loop constraint is: the sides of the first boundary closed loop form a closed loop; in, Let be the normal vector of the closed loop of the first boundary. Let be the normal vector of the outer surface of the first boundary closed wireframe. Let be the normal vector of the side of the closed bounding box. As the first constraint angle, For the second constraint angle, This is an operation to find the angle between two vectors.
6. The method for identifying hole features in a 3D model based on B-Rep topology according to claim 1, characterized in that, The rounded edge constraint is: the included angle between two adjacent faces of the edge containing the search point is 0; The tangency constraint is: the edge containing the search point is tangent to the adjacent edge to be searched or the included angle is the smallest; The curvature constraint is: the curvature of the outer surface of the edge containing the search point is less than the curvature of the side surface of that edge; The angular constraint of the adjacent outer surfaces of the rounded edge is: the outer surface of the edge where the search point is located is tangent to the outer surface of the adjacent edge to be searched or the included angle is less than the third preset angle.
7. The method for identifying hole features in a 3D model based on B-Rep topology according to claim 1, characterized in that, During the path search process, the searched points of the current path are saved to the history list of searched points, and a search point not in the history list is selected as the next search point for the current path.
8. A device for identifying hole features in a three-dimensional model based on B-Rep topology, characterized in that, include: An in-plane hole identification module, used to search for in-plane holes, includes: The closed wireframe acquisition unit is used to traverse each outer surface of the 3D model and acquire the inner loop located on the outer surface of the 3D model, which is denoted as the in-plane closed wireframe. The concavity / convexity detection unit is used to perform concavity / convexity detection on the edges of an in-plane closed frame. If the edge of the in-plane closed frame is a convex edge, then the in-plane closed frame is an in-plane hole. If the edge of the in-plane closed frame is a rounded edge, then the concavity / convexity of the side surface of the in-plane closed frame is determined by the ray method. If the side surface of the in-plane closed frame is a concave surface, then the in-plane closed frame is an in-plane hole. A non-rounded corner hole recognition module is used to search for holes with non-rounded corners, including: The non-rounded corner hole path search unit is used to search for a path starting from any point on the outer ring of the outer surface of the 3D model, using non-rounded corner constraints, adjacent outer surface constraints of non-rounded corners, and side constraints of non-rounded corners, until the path forms a loop and the first boundary closed wireframe is obtained. The non-rounded corner hole constraint detection unit is used to determine if the first boundary closed frame is a non-rounded corner hole if it satisfies the circumferential detection constraint, the angle constraint, the normal constraint, and the side loop constraint. A rounded corner hole recognition module is used to search for rounded corner holes, including: The rounded edge hole path search unit is used to search for a path starting from any point on the outer ring of the outer surface of the 3D model, using rounded edge constraints, tangency constraints, curvature constraints and angular constraints of the outer surfaces adjacent to the rounded edge, until the path forms a loop and the second boundary closed wireframe is obtained. A rounded corner hole constraint detection unit is used to determine if a second boundary closed frame is a rounded corner hole if it satisfies the circumduction detection constraint.
9. A device for identifying hole features in a 3D model based on B-Rep topology, characterized in that, include: Memory, used to store computer programs; A processor, configured to execute the computer program to implement the steps of the method for identifying hole features in a three-dimensional model based on B-Rep topology as described in any one of claims 1 to 7.
10. A computer program product, comprising a computer program, characterized in that, When executed by a processor, the computer program implements the steps of a method for identifying hole features in a three-dimensional model based on B-Rep topology as described in any one of claims 1 to 7.