B-Rep model simplification method based on fillet feature network

Abstract

The invention belongs to the field of boundary representation model transition feature simplification, and relates to a B-Rep model simplification method based on a fillet feature network. According to the method, based on the fillet radius of the fillet feature, accurate construction and reasonable classification of the fillet feature network are realized by combining the concavity and convexity of the fillet feature and whether the fillet feature is degraded or not, and the fillet feature network comprises equal-radius and non-equal-radius fillet feature networks. The equal-radius fillet feature network represents fillet surfaces possibly created in the same rounding operation, the variable-radius fillet feature network is an adjacent complex fillet surface set and can be inhibited through extension intersection of supporting surfaces, and the remaining fillet surfaces are inhibited through additional Boolean union and Boolean subtraction operations. And finally, high-precision identification and robust suppression of the fillet features are realized. According to the method, the problem that the design is limited due to insufficient generalization ability and robustness of fillet feature identification on a multi-scale heterogeneous model during the optimization design of the physical field characteristics of the existing product is solved.

Description

Technical Field

[0001] This invention belongs to the field of transition feature simplification of boundary representation (B-Rep) models, and relates to a B-Rep model simplification method based on rounded corner feature networks. Background Technology

[0002] In computer-aided design (CAD), the fillet feature is a common feature that refers to the rounding off of edges or corners in a boundary representation (B-Rep) model, replacing sharp edges or corners with smooth, rounded transition surfaces. This treatment is widely used in product structural design, as it effectively reduces stress concentration, improves the appearance quality of products, and enhances their safety, aesthetics, and manufacturability.

[0003] However, when fillets are introduced into Computer-Aided Engineering (CAE), they often become a major obstacle to simulation analysis. On the one hand, fillets introduce complex nonlinear surfaces, significantly increasing the complexity of geometric and topological processing. This often causes geometric operations such as Boolean operations, feature recognition, and model simplification to fail, and may even disrupt the identification and reconstruction of the main feature structure. On the other hand, during the finite element mesh generation stage, fillet regions are divided into a large number of dense small elements. This not only significantly increases computational costs but also introduces risks such as decreased element quality and poor convergence, affecting error estimation and simulation accuracy. Therefore, in the process of optimizing the physical field characteristics of a product, it is necessary to identify and suppress fillet features to improve the robustness of geometric processing and ensure that subsequent simulation analysis can be carried out smoothly and efficiently.

[0004] At the recognition level, rounded corner features are automatically extracted by analyzing geometric indicators such as curvature distribution, face-edge topological relationships, and curvature continuity. There are also topological graph-based structural recognition methods that form loops based on adjacency relationships of rounded corner faces and then identify their variable or constant radius features. These recognition algorithms are relatively complete, but they still face challenges in terms of stability when dealing with complex CAD models that include free-form surfaces, hybrid structures, and nonparametric models.

[0005] Similarly, at the suppression level, common methods include: reversing the rounded corners to their original straight edge structure, constructing equivalent chamfers and replacing the rounded corners with Boolean operations, and filling the gaps left by the deleted rounded corners by extending adjacent sides or patching holes, thereby restoring the geometry used for analysis. These methods effectively enhance the simplification capability of the target geometry, but they may still encounter problems such as boundary mismatch and Boolean failure when faced with extremely high surface complexity.

[0006] Researchers have focused on improving the completeness of rounded corner feature recognition methods and the robustness of rounded corner feature suppression algorithms, and these methods have achieved good results. However, rounded corner feature recognition remains an unsolved problem, and the generalization ability of recognition algorithms across multiple scales and heterogeneous models, as well as the robustness of rounded corner feature suppression algorithms, need further improvement. Summary of the Invention

[0007] To address the aforementioned problems and shortcomings, and to resolve the limitations imposed by insufficient generalization ability and robustness of rounded corner feature recognition across multi-scale and heterogeneous models in the optimization design of existing product physical field characteristics, this invention provides a simplified B-Rep model based on rounded corner feature networks. This invention, based on the rounded corner radius of the rounded corner feature, combined with the concavity / convexity and whether the rounded corner feature is degenerate, achieves accurate construction and reasonable classification of rounded corner feature networks, including equal-radius and non-equal-radius rounded corner feature networks. Equal-radius rounded corner feature networks represent rounded corner surfaces that may be created in the same rounding operation, while variable-radius rounded corner feature networks are sets of adjacent complex rounded corner surfaces, all of which can be suppressed by extending and intersecting the supporting surfaces. Additional Boolean union and Boolean subtraction operations are applied to the remaining rounded corner surfaces for suppression, ultimately achieving high-precision recognition and robust suppression of rounded corner features.

[0008] A simplified B-Rep model based on rounded corner feature networks includes the following steps:

[0009] Step 1: Import the B-Rep entity model M, and input the range of rounded corner feature radii that the user expects to detect and suppress, as the basis for rounded corner feature recognition; including the maximum rounded corner feature radius r. max and minimum fillet feature radius r min Simultaneously, find and obtain the list E of all edges and the list F of all faces of model M, where the number of edges is N. E The number of faces is N F .

[0010] A fillet feature is a set of adjacent fillet transition surfaces, or it can be a single edge fillet transition surface. The fillet transition surface (fillet surface) is a smooth surface generated by rounding a rolling sphere (a sphere that rolls along the angle between the intersection of two surfaces). It is a portion of the area traversed by the sphere's surface during its rolling motion. The radius of the rolling sphere serves as the radius of the fillet transition surface. Fillet transition surfaces include constant radius fillet transition surfaces (generally analytical surfaces, such as cylindrical surfaces, tori, and spheres) and variable radius fillet transition surfaces (often spline surfaces).

[0011] The edge rounded transition surface (edge ​​rounded surface) is a rounded transition surface that replaces the edges of the original model, and after suppression, it corresponds to an edge. The point rounded transition surface (point rounded surface) is a rounded transition surface that replaces the corners of the original model, and after suppression, it corresponds to a vertex.

[0012] Step 2: Traverse the entire edge list E of model M and determine the edge e. i The smoothness (smooth edge or sharp edge) of the edge, where 0≤i≤N E Then mark them. Store all smooth edges in the smooth edge list E. G .

[0013] A smooth edge in a B-Rep model is an edge where two adjacent surfaces share a common edge that satisfies at least G1 (tangential plane continuity) or higher geometric continuity (such as G2 curvature continuity). Smooth edges ensure a smooth transition between surfaces, without visually or tactilely sharp edges. Conversely, a sharp edge is where two adjacent surfaces coincide only at the edge, but the tangent direction is discontinuous.

[0014] Step 3: Traverse the list F of all faces of the model, and for the curved surfaces f other than the planes... j Extract the corresponding edge list Where 0≤j≤N F Using the smooth edge list E obtained in step 2 G judge Number of smooth edges

[0015] like Identify surface f j To prepare a rounded corner, calculate its fillet radius.

[0016] like Then continue searching for the surface f. j If planes adjacent to each other through smooth edges can be extended to intersect or be parallel, then the surface f is considered to be... j For rounded surfaces, these adjacent planes are considered as rounded surfaces f. j The supporting surfaces are identified and stored in the corresponding supporting surface list. Store all rounded faces in the first rounded face list.

[0017] In the B-Rep model, analytic surfaces are a class of geometric surfaces that can be directly described by precise mathematical equations. These include planes, cylinders, tori, and spheres. Their core characteristic is that their geometry is defined by closed mathematical formulas (analytic equations), without relying on discrete points or approximation algorithms. Therefore, for analytic surfaces, when considered as pre-filled surfaces, their fillet radii can be obtained through analytical equations: for cylinders, the radius of the cylinder's base is used as the fillet radius; for tori, the minor radius of the tori is used; and for spheres, the radius of the sphere is used.

[0018] The supporting surface refers to the plane that supports the rolling ball operation, which is adjacent to the rounded corner surface through a smooth edge.

[0019] Spline surfaces are smooth surfaces defined by parametric mathematical functions. They typically consist of a set of control points and basis functions, and are a type of parametric surface capable of flexibly representing complex shapes. Therefore, the fillet radius of a spline surface cannot be directly obtained like that of an analytical surface.

[0020] The following fillet radius calculation method is applied to all spline surfaces, treating them all as constant radius fillet surfaces. The calculation method is as follows: On spline surface f... S Up-random sampling Calculate these points respectively. The set of maximum principal curvatures of points on the surface and the set of minimum principal curvatures After sorting the values ​​in ascending order, the first 25% and the last 25% are removed respectively. The mean values ​​μ1 and μ2 of the remaining values ​​are then calculated, and the corner radius is taken.

[0021] Step 4: Traverse the list of first rounded corner faces Classify and distinguish concave rounded corners, convex rounded corners, degenerate rounded corners, and non-degenerate rounded corners.

[0022] Concavity / convexity classification: for any rounded corner surface f Υ The concavity / convexity is determined by the signed principal curvature κ at any sampling point on the surface. If κ < 0, the rounded surface f Υ Mark as a concave rounded corner surface; otherwise, mark as a convex rounded corner surface. The principal curvatures (maximum principal curvature κ1 and minimum principal curvature κ2) of the surface sampling points. If the absolute value of κ1 is equal to the rounded corner surface f... Υ If the fillet radius values ​​are the same, then κ = κ1; conversely, if the absolute value of κ2 is the same as that of the fillet surface f, then κ = κ1. Υ If the fillet radii are the same, then κ = κ2; if both are different, then κ = κ1 is taken by default.

[0023] Degeneracy classification: Only rounded corners f Υ Degeneration is only possible when the geometry is cylindrical; if the fillet surface f... Υ If the two supporting surfaces are parallel to each other, then f Υ Mark it as a degenerate fillet; otherwise mark it as a non-degenerate fillet.

[0024] A convex rounded corner is formed by rounding the convex edges, which reduces the volume of the solid model; while a concave rounded corner is formed by rounding the concave edges, which increases the volume of the solid model.

[0025] The two supporting surfaces of a degenerate fillet are parallel to each other. This situation generally only occurs with fillets of cylindrical geometry. It cannot be suppressed by simply extending the supporting surfaces to intersect. Therefore, it needs to be identified so that additional suppression can be carried out later.

[0026] Step 5, Search The rounded surface with the smallest current fillet radius

[0027] like For non-degenerate rounded corner surfaces, construct their maximum equal-radius rounded corner feature network. The number of rounded corners is

[0028] Using equal radius rounded corner feature network f of each rounded corner face m List of support surfaces in Construct a set of support surfaces Delete in B-Rep entity model M All rounded corners in the middle. For Extend and intersect all supporting surfaces. If the extension and intersection are successful, there are no gaps in the solid model. Delete the existing The rounded corners; otherwise, if the extension fails to find the intersection, restore the B-Rep solid model M, from Delete And Also save it to the second rounded corner list.

[0029] Otherwise, if To degenerate a rounded corner, then from Delete And Also save it to the third rounded corner list.

[0030] Until the list of rounded corners Empty.

[0031] Second Rounded Corner List This is the first list of rounded corner faces. A subset of the third rounded face list is provided to ensure robustness of rounded face suppression. Also the first rounded corner list A subset of, and the list of second rounded faces The purpose of intersecting (as described in step 6) is to suppress rounded and degenerate rounded surfaces that cannot be suppressed by the aforementioned operations.

[0032] Step 6, Search The rounded surface with the smallest current fillet radius Construct its maximum non-uniform radius rounded corner feature network The number of rounded corners is

[0033] Using non-uniform radius rounded corner feature network f of each rounded corner face n List of support surfaces in Construct a set of support surfaces Delete in B-Rep entity model M All sides of the middle, Extend and intersect each face in the model. If the extension and intersection are successful, there are no gaps in the solid model. Delete the existing The rounded corners; otherwise, if the extension fails to find the intersection, restore the B-Rep solid model M, from Delete And Also save it to the third rounded corner list.

[0034] Until the list of rounded corners Empty.

[0035] Step 7: Traverse the list of rounded corner faces The number of rounded corners is On the rounded corner f k Calculate an circumscribed bounding box at the location. in If f k If the surface has concave rounded corners, then surround the box with the surface. For the tool body, subtract it from the B-Rep entity model M; otherwise, if f k If the surface has convex rounded corners, then enclose the box with the surface. The tool body is used to perform a Boolean union with the B-Rep entity model M.

[0036] Step 8: Complete the rounded corner feature recognition and suppression, and return the simplified B-Rep entity model M. simple .

[0037] Furthermore, in step 5, since all rounded faces in the equal radius rounded corner feature network are necessarily adjacent and have the same rounded corner radius, the search for the equal radius rounded corner feature network can be accelerated using face-edge graphs, dynamic programming algorithms, etc.

[0038] Furthermore, in step 5, when determining whether the supporting surfaces can be extended to intersect, the "Extend Surface" function or "Topology Extending" function of the B-Rep solid model can be used, or extension can be performed manually in the parameter domain (this is simpler for analytical surfaces, but may require extension in the UV parameter domain or at the control vertex level for spline surfaces). After the surface is extended, surface-to-surface intersection can be performed to determine whether there are intersecting lines or points between the extended surfaces.

[0039] Furthermore, in step 6, since each rounded face in the non-uniform radius rounded corner feature network is necessarily adjacent, but the rounded corner radii may be different, the search for the non-uniform radius rounded corner feature network can be accelerated by using face-edge graphs, dynamic programming algorithms, etc.

[0040] Furthermore, the suppression of degenerate fillet faces in step 7 is achieved by calculating an circumscribed bounding box (usually a cube) at the location of each degenerate fillet face, and then performing a Boolean union or subtract operation with the solid model. This operation can also serve as a safeguard to suppress fillet faces that cannot be suppressed by the aforementioned support surface extension and intersection operation.

[0041] Furthermore, the simplified B-Rep model based on the rounded corner feature network described above only requires the user to provide a limit on the rounded corner feature radius, i.e., the maximum rounded corner feature radius r. max and minimum fillet feature radius r min It can automatically identify and adaptively suppress all rounded corner features within the constraints: for example, for general non-degenerate rounded corners, it uses the method of supporting surface extension and intersection to suppress them; while for degenerate rounded corners, it uses Boolean operations between the bounding box of the outer face and the solid model to suppress them.

[0042] This invention addresses the challenges posed by rounded corner features in B-Rep models to computer-aided engineering. To improve the robustness and efficiency of geometric processing and ensure smooth subsequent simulation analysis and manufacturing processes, it delves into rounded corner feature recognition and suppression techniques, proposing a model simplification technique based on rounded corner feature networks. First, smooth edge detection is used to prepare rounded corner surfaces. Based on a user-input rounded corner radius threshold, effective rounded corner surfaces are further determined. Combining the concavity / convexity of rounded corner features, their degeneracy, and their adjacency with rounded corner surfaces, all rounded corner surfaces are divided into equal-radius, non-equal-radius, and degenerate rounded corner feature networks. Subsequently, using a support surface extension and intersection technique, equal-radius and non-equal-radius rounded corner feature networks are suppressed sequentially, thereby suppressing edge-rounded corner surfaces as edges and point-rounded corner surfaces as points. Boolean operations are then used to further suppress the remaining degenerate rounded corner feature networks and rounded corner surfaces that failed to be suppressed by the aforementioned techniques. This achieves accurate and robust suppression of rounded corner features while maintaining the effectiveness of the model's topology and geometry. Verification results through model simplification examples demonstrate that this invention achieves high-precision recognition and robust suppression of rounded corner features.

[0043] In summary, this invention first utilizes smooth edge detection to prepare rounded corner surfaces. Based on the user-input rounded corner radius threshold, it further determines the effective rounded corner surfaces and, considering the concavity / convexity and whether the rounded corner features are degenerate, divides them into equal-radius and non-equal-radius rounded corner feature networks. Subsequently, it uses the support surface extension and intersection technique to suppress these two types of networks sequentially, thereby suppressing edge-rounded corner surfaces as edges and point-rounded corner surfaces as points. Boolean operations are then used to further suppress the remaining degenerate rounded corner surfaces and those rounded corner surfaces that failed to be suppressed by the aforementioned techniques, achieving accurate and robust suppression of rounded corner features while maintaining the effectiveness of the model's topology and geometry. Furthermore, this invention only requires the user to provide a limit on the rounded corner feature radius (maximum rounded corner feature radius r). max and minimum fillet feature radius r min This invention can automatically identify and adaptively suppress rounded corner features within all constraints. Compared to existing technologies (commercial software HyperMesh), the rounded corner feature recognition of this invention is more accurate and comparable to commercial software, but the suppression rate is much higher, reaching 79.8%, while commercial software only achieves 56.9%. Attached Figure Description

[0044] Figure 1 This is a flowchart of the present invention;

[0045] Figure 2 This is a three-dimensional model diagram of an embodiment;

[0046] Figure 3 This is a comparison of the rounded corner feature detection results between the example and the commercial software HyperMesh;

[0047] Figure 4This is a comparison of the rounded corner feature suppression results between the example and the commercial software HyperMesh. Detailed Implementation

[0048] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0049] Example

[0050] A simplified B-Rep model based on rounded corner feature networks, referring to... Figure 1 This includes the following steps:

[0051] Step 1: Import the B-Rep entity model M, and input the range of rounded corner feature radii that the user expects to detect and suppress, as the basis for rounded corner feature recognition, including the maximum rounded corner feature radius r. max and minimum fillet feature radius r min Simultaneously, find and obtain the list E of all edges and the list F of all faces of the model, where the number of edges is N. E The number of faces is N F .

[0052] This embodiment uses a pistol model as an example to establish... Figure 2 The model structure shown. This model has rich and complex rounded corner features, such as... Figure 2 As shown in the marked area in (b), these rounded corner features include not only analytical surfaces such as cylinders, tori, and spheres, but also a large number of spline surfaces, and simultaneously cover both equal-radius and non-equal-radius rounded corner feature networks. Furthermore, degenerate rounded corner surfaces also exist in the model, further increasing the complexity of rounded corner feature recognition and posing a challenge to the robustness of the algorithm.

[0053] Step 2: Traverse the entire edge list E of the model and determine the edge e. i The smoothness (smooth edge or sharp edge) of the edge, where 0≤i≤N E Then mark them. Store all smooth edges in the smooth edge list E. G .

[0054] Step 3: Traverse the list F of all faces of the model, and for the curved surfaces f other than the planes... j Extract the corresponding edge list Where 0≤j≤N F Using the smooth edge list E obtained in step 2 G judge Number of smooth edges like Identify surface f j To prepare a rounded corner, calculate its fillet radius. like Then continue searching for the surface f. jIf planes adjacent to each other through smooth edges can be extended to intersect or be parallel, then the surface f is considered to be... j For rounded surfaces, these adjacent planes are considered as rounded surfaces f. j The supporting surfaces are identified and stored in the corresponding supporting surface list. Store all rounded faces in the first rounded face list.

[0055] Step 4: Traverse the list of first rounded corner faces Classify and distinguish concave rounded corners, convex rounded corners, degenerate rounded corners, and non-degenerate rounded corners.

[0056] Step 5, Search The rounded surface with the smallest current fillet radius

[0057] like For non-degenerate rounded corner surfaces, construct their maximum equal-radius rounded corner feature network. The number of rounded corners is

[0058] Using equal radius rounded corner feature network f of each rounded corner face m List of support surfaces in Construct a set of support surfaces Delete in B-Rep entity model M All sides of the middle, Extend and intersect each face in the model. If the extension and intersection are successful, there are no gaps in the solid model. Delete the existing The rounded corners; otherwise, if the extension fails to find the intersection, restore the B-Rep solid model M, from Delete And Also save it to the second rounded corner list.

[0059] Otherwise, if To degenerate a rounded corner, then from Delete And Also save it to the third rounded corner list.

[0060] Until the list of rounded corners Empty.

[0061] Step 6, Search The rounded surface with the smallest current fillet radius Construct its maximum non-uniform radius rounded corner feature network The number of rounded corners is

[0062] Using non-uniform radius rounded corner feature network f of each rounded corner face n List of support surfaces in Construct a set of support surfaces Delete in B-Rep entity model M All sides of the middle, Extend and intersect each face in the model. If the extension and intersection are successful, there are no gaps in the solid model. Delete the existing The rounded corners; otherwise, if the extension fails to find the intersection, restore the B-Rep solid model M, from Delete And Also save it to the third rounded corner list.

[0063] Until the list of rounded corners Empty.

[0064] Step 7: Traverse the list of rounded corner faces The number of rounded corners is On the rounded corner f k Calculate an circumscribed bounding box at the location. in If f k If the surface has concave rounded corners, then surround the box with the surface. For the tool body, subtract it from the B-Rep entity model M; otherwise, if f k If the surface has convex rounded corners, then enclose the box with the surface. The tool body is used to perform a Boolean union with the B-Rep entity model M.

[0065] Step 8: Complete the rounded corner feature recognition and suppression, and return the simplified B-Rep entity model M. simple .

[0066] Figure 3 (a) then details the method of the embodiments of the present invention. Figure 2 The overall recognition result of rounded corner features in the model. As can be seen from the figure, the method of the present invention accurately identifies rounded corner features in different regions and successfully classifies them into different types of rounded corner feature networks within the method, providing reliable input data for the subsequent rounded corner feature suppression process. Figure 3 (b) The results of rounded corner feature recognition using the commercial software HyperMesh are shown. It is clear that the method proposed in this invention achieves recognition accuracy comparable to that of commercial software, proving that this invention can recognize all valid rounded corner features.

[0067] Figure 4 (a) This paper visually demonstrates the specific effect of suppressing the identified rounded corner features using the method proposed in this invention, further verifying the robustness and accuracy of the method. By comparing the models before and after suppression, it is clearly observed that the topological structure and geometric continuity of the rounded corner features are effectively preserved after accurate identification and removal, and the simplification effect of complex feature regions is also readily apparent. Figure 4 (b) The results of rounded corner feature suppression using the commercial software HyperMesh are shown. It is evident that the commercial software fails to effectively suppress rounded corner features in many locations, leading to geometric problems such as intersections and incorrect edges, with a rounded corner feature suppression rate of only 56.9%. In contrast, the method proposed in this invention successfully completes the suppression operation, achieving a suppression rate of 79.8% for the identified rounded corner features, without exhibiting similar geometric errors.

[0068] As can be seen from the above embodiments, the present invention demonstrates accuracy in processing complex rounded corner features and robust suppression capabilities for various types of rounded corner features. Furthermore, the present invention only requires the user to provide a limit on the rounded corner feature radius, i.e., the maximum rounded corner feature radius r. max and minimum fillet feature radius r min It can automatically identify and adaptively suppress all rounded corner features within the constraints.

Claims

1. A simplified B-Rep model based on a rounded corner feature network, characterized in that, Includes the following steps: Step 1: Import the B-Rep entity model M, and input the range of rounded corner feature radii that the user expects to detect and suppress, as the basis for rounded corner feature recognition; including the maximum rounded corner feature radius r. max and minimum fillet feature radius r min Simultaneously, find and obtain the list E of all edges and the list F of all faces of model M, where the number of edges is N. E The number of faces is N F ; Rounded corner transition surfaces include constant radius rounded corner transition surfaces and variable radius rounded corner transition surfaces; while edge rounded corner transition surfaces are rounded corner transition surfaces that replace the edges of the original model, and after suppression, they correspond to an edge; point rounded corner transition surfaces are rounded corner transition surfaces that replace the corners of the original model, and after suppression, they correspond to a vertex. Step 2: Traverse the entire edge list E of model M and determine the edge e. i Let i be a smooth edge or a sharp edge, where 0 ≤ i ≤ N E Mark the smooth edges; store all smooth edges in the smooth edge list E. G ; A smooth edge is an edge in the B-Rep model where two adjacent surfaces share a common edge that satisfies at least G1 continuity in the tangent plane; an acute edge is an edge where two adjacent surfaces coincide only at the edge, but the tangent directions are discontinuous. Step 3: Traverse the list F of all faces of the model, and for the curved surfaces f other than the planes... j Extract the corresponding edge list Where 0≤j≤N F Using the smooth edge list E obtained in step 2 G judge Number of smooth edges like Identify the surface f j To prepare a rounded corner, calculate its fillet radius. like Then continue searching for the surface f. j If planes adjacent to each other through smooth edges can be extended to intersect or be parallel, then the surface f is considered to be... j For rounded surfaces, these adjacent planes are considered as rounded surfaces f. j The supporting surfaces are identified and stored in the corresponding supporting surface list. Store all rounded faces in the first rounded face list. In the B-Rep model, when an analytical surface is considered a pre-filled surface, its fillet radius is obtained through analytical equations: for a cylindrical surface, the radius of the base of the cylinder is used as the fillet radius; for a torus, the secondary radius of the torus is used as the fillet radius; and for a sphere, the radius of the sphere is used as the fillet radius. The supporting surface refers to the plane that supports the operation of the rolling ball, and it is adjacent to the rounded corner surface through a smooth edge; The following fillet radius calculation method is adopted for all spline surfaces, and they are all regarded as constant radius fillet surfaces. The calculation method is as follows: On spline surface f S Up-random sampling Calculate these points respectively. The set of maximum principal curvatures of points on the surface and the set of minimum principal curvatures After sorting the values ​​in ascending order, the first 25% and the last 25% are removed respectively. The mean values ​​μ1 and μ2 of the remaining values ​​are then calculated, and the corner radius is taken. Step 4: Traverse the list of first rounded corner faces Classify and distinguish concave rounded corners, convex rounded corners, degenerate rounded corners, and non-degenerate rounded corners; Concavity / convexity classification: for any rounded corner surface f Υ The concavity / convexity is determined by the signed principal curvature κ at any sampling point on the surface. If κ < 0, the rounded surface f Υ Mark it as a concave fillet surface; otherwise, mark it as a convex fillet surface. The maximum principal curvature κ1 and minimum principal curvature κ2 of the surface sampling points, if the absolute value of κ1 is equal to that of the rounded surface f Υ If the fillet radius values ​​are the same, then κ = κ1; conversely, if the absolute value of κ2 is the same as that of the fillet surface f, then κ = κ1. Υ If the fillet radii are the same, then κ = κ2; if both are different, then κ = κ1 is taken by default. Degeneracy classification: Only rounded corners f Υ Degeneration is only possible when the geometry is cylindrical; if the fillet surface f... Υ If the two supporting surfaces are parallel to each other, then f Υ Mark as a degenerate fillet; otherwise mark as a non-degenerate fillet. A convex rounded corner is formed by rounding the convex edges, which reduces the volume of the solid model; while a concave rounded corner is formed by rounding the concave edges, which increases the volume of the solid model. Step 5, Search The rounded surface with the smallest current fillet radius like For non-degenerate rounded corner surfaces, construct their maximum equal-radius rounded corner feature network. The number of rounded corners is Using equal radius rounded corner feature network f of each rounded corner face m List of support surfaces in Construct a set of support surfaces Delete in B-Rep entity model M All sides of the middle, Extend and intersect all supporting surfaces. If the extension and intersection are successful, there are no gaps in the solid model. Delete the existing The rounded corners; otherwise, if the extension fails to find the intersection, restore the B-Rep solid model M, from Delete And Also save it to the second rounded corner list. Otherwise, if To degenerate a rounded corner, then from Delete And Also save it to the third rounded corner list. Until the list of rounded corners Empty; Second Rounded Corner List This is the first list of rounded corner faces. A subset of the third rounded face list is provided to ensure robustness of rounded face suppression. Also the first rounded face list A subset of, and the list of second rounded faces intersect; Step 6, Search The rounded surface with the smallest current fillet radius Construct its maximum non-uniform radius rounded corner feature network The number of rounded corners is Using non-uniform radius rounded corner feature network f of each rounded corner face n List of support surfaces in Construct a set of support surfaces Delete in B-Rep entity model M All sides of the middle, Extend and intersect each face in the model. If the extension and intersection are successful, there are no gaps in the solid model. Delete the existing The rounded corners; otherwise, if the extension fails to find the intersection, restore the B-Rep solid model M, from Delete And Also save it to the third rounded corner list. Until the list of rounded corners Empty; Step 7: Traverse the list of rounded corner faces The number of rounded corners is On the rounded corner f k Calculate an circumscribed bounding box at the location. in If f k If the surface has concave rounded corners, then surround the box with the surface. For the tool body, subtract it from the B-Rep entity model M; otherwise, if f k If the surface has convex rounded corners, then enclose the box with the surface. As the tool body, perform a Boolean union with the B-Rep entity model M; Step 8: Complete the rounded corner feature recognition and suppression, and return the simplified B-Rep entity model M. simple .

2. The simplified B-Rep model based on rounded corner feature networks as described in claim 1, characterized in that: In step 5, the search for the equal-radius rounded corner feature network is accelerated using face-edge graphs or dynamic programming algorithms.

3. The simplified B-Rep model based on rounded corner feature networks as described in claim 1, characterized in that: In step 5, when determining whether the support surfaces can be extended to intersect, the extension function of the B-Rep solid model, the topology extension function, or manual extension in the parameter domain is used; after the surface is extended, the surface intersection is calculated, and then it is determined whether there are intersecting lines or points between the extended surfaces.

4. The simplified B-Rep model based on rounded corner feature networks as described in claim 1, characterized in that: In step 6, the search for non-uniform radius rounded corner feature networks is accelerated using face-edge graphs or dynamic programming algorithms.

5. The method for simplifying the B-Rep model based on rounded corner feature networks as described in claim 1, characterized in that, The suppression of degenerate fillet faces in step 7 is achieved by calculating an circumscribed bounding box at the position of each degenerate fillet face, and then performing a Boolean union or Boolean subtraction operation with the solid model.

6. The method for simplifying the B-Rep model based on rounded corner feature networks as described in claim 1, characterized in that: The maximum fillet feature radius r is limited by the user-provided fillet feature radius constraint. max and minimum fillet feature radius r min It automatically identifies and adaptively suppresses all rounded corner features within the constraints: for general non-degenerate rounded corners, it uses the method of supporting surface extension and intersection to suppress them; while for degenerate rounded corners, it uses Boolean operations between the bounding box of the outer face and the solid model to suppress them.

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