Research On Feature-oriented CAD Mesh Simplification Algorithm

In order to improve the rendering efficiency and quality of three-dimensional visualization scenes,the CAD mesh model simplification has become an indispensable procedure in many complex C AD/CAE applications such as virtual reality,digital factories and finite element analysis.C urrent CAD/CAE applications always uses the graphics mesh simplification to simplify the C AD mesh.Although graphics mesh simplification algorithms do reduce the overall number of patches to some extent,but the quality of simplified CAD mesh is poor.And the loss of structural features of the CAD model is quite serious.In order to overcome the above problem,this paper makes a profound study on the CAD mesh simplification and proposes a feature-oriented CAD mesh simplification algorithm.The main research is as follows:1.Propose a boundary information extraction method for the CAD mesh.Since the expression of the features needs to use the regional boundary information of the C AD mesh,and the CAD mesh itself lacks the regional boundary information,this paper proposes a boundary information extraction method for the CAD mesh.This method firstly uses the watershed mesh segmentation algorithm to process the CAD mesh with the undivided region according to the consistency of the curvature of the CAD mesh region,and then extracts the boundary information of mesh regions by using topological propery of the orientable manifold mesh.Lastly calculated the topology connection information between mesh regions based on the region boundary intersection principle.This method can efficiently convert the CAD mesh into the mesh model with B-Rep boundary expression,and generate the attribute adjacency graph of the CAD mesh for the extraction of the structural features of the mesh model.2.Propose an automatic feature recognition method based on graph matching.Since the mesh simplification is to simplify regions near the relevant structural features,and the internal structural features of the mesh are diverse,it is convenient to manually recognize.Therefore,this paper makes a profound study on the automatic feature recognition algorithm based on graph matching.This paper proposes an automatic feature recognition framework for C AD mesh models,and deeply studies the key subgraph matching algorithm.Combined with the regional bo undary feature of the mesh model,the quadratic decomposition algorithm of the attribute adjacency graph to obtain the collection of structural features.This algorithm makes full use of the regional boundary information of the C AD mesh,and automatically extracts the structural features to be simplified more efficiently and ensures the reusability of structural feature recognition.3.Propose a region simplification method based on edge collapse and boundary collapse.Aiming at the problem that the features are relatively regular and the patch redundancy is really strong near the structural features of the CAD mesh,this paper proposes a region simplification method based on edge collapse and boundary collapse.In this method,the feature suppression is used to simplify mesh regions.Firstly,the feature regions corresponding to the structural features are deleted.After the features are deleted,the boundary collapse operation is used to repair the residual boundaries and the adjacent vertex topological connectivity near the repaired holes is tracked.Finally the mesh are is simplified and optimized by using multiple edge collapse operation to ensure that there are no redundant patches inside the mesh region.This method uses topological operations such as edge collapse and boundary collapse to efficiently remove redundant patches inside the mesh region to avoid triangulation of meshes,and ensure the simplification efficiency.Based on the main research,a CAD mesh simplification system prototype is developed independently,and the general system architecture of the C AD mesh simplification is proposed.Finally the feasibility of the proposed algorithm is verified by a practical example.It provide reference and guidance for three-dimensional CAD mesh simplification algorithms.