A Study On 3D Data Transformation Between Parasolid And STL

Data format transformation among different systems is the prerequisite of the realization of CAD/CAM integration. The geometry modeling function of Parasolid modeling kernel is extremely powerful, which is widely applied in many commercial CAD/CAM softwares, such as: Unigraphics, SolidWorks and SolidEdge, etc. STL(Stereo Lithography) is the de facto standard interface for data exchange in rapid prototyping system, meanwhile, which is also widely used in CNC machining, reverse engineering and other fields. The study on 3D data transformation between Parasolid and STL carried out in this paper has an important theoretical and practical significance for improving data exchange and sharing in CAD/CAM system, and has a significant contribution to promote CAD/CAM system with independent intellectual property rights. Main tasks are as follows:First, methods of reading and writing the Parasolid file and STL file were given. How to visualize the data model and operate the graphics was introduced. And a platform of data transformation between Parasolid and STL was established. Secondly, an algorithm on data transformation from Parasolid to STL was presented. The Parasolid model was triangulated according the consistency rule of STL model by utilizing the function of PK_TOPOL_facet() in Parasolid modeling kernel; topological relations of triangular facets with their vertex and normal vector were built through the return topology information; and then the data transformation from Parasolid to STL was realized. Finally, an algorithm on data transformation from STL to Parasolid was proposed. On the basis of segmentation for triangular mesh model, the boundary of triangular mesh model was sectioned by using the corner points; feature points were selected using the approximation midpoint on the border of each section and recursion subdivision algorithm; the shortest paths between two corresponding character points on the corresponding border sections were calculated by adopting Dijkstra algorithm to get interpolation data of space tetragonal; free-form surfaces of the triangular mesh model were reconstructed by the interpolation method and sewed by using Parasolid functions, thereby the STL model was transformed into Parasolid files. This paper achieves the system implementation of 3D data transformation between Parasolid and STL in the Windows XP environment using Visual C++, OpenGL and Parasolid modeling kernel. Application example indicates that the proposed algorithm in this paper can implement the two-way 3D data transformation between Parasolid and STL. The program runs stable and reliable.