Design And Implementation Of CAD Geometric Modeling System Based On Parasolid

The geometric modeling is the basis technique of computer-aided design and analysis with optimization. Existing foreign commercial CAD softwares for geometric modeling are far from meeting the requirements of a specific type of product specialization and intelligent design, and the secondary development is alse difficult to fulfill the target expectations; due to the lack of independent research of geometric modeling techniques, the development China’s of high-end applications in the field of aerospace and national defense is severely constrained, the implementation of digital manufacturing technology, especially a number of key technologies such as computer simulation can not get effective support,so the research and development of geometry modeling system with independent intellectual property has great significance importance.Subject to the actual project development of ThermoSolid, which is a3D CAD geometric modeling system, is based on Parasolid graphics core.A variety of2D drafting and3D solid parametric modeling approach is provided, we alse provide realistic graphics scene setting function, as well as the follow-up mesh finite element solver interface and visualization functions as basis support.The geometric modeling technique involves the knowledge of CAGD, which is known as Computer Aided Geometrical Design, and computer graphics and software development methods. The preparatory work includes the learning of OpenGL graphics library, the using and testing of the Parasolid development platform, as well as the learning of software development theories and methods. On the basis of these preparations completed, three functions of the geometric modeling system are achieved: two-dimensional sketch, three-dimensional solid body generation and realistic graphics.Seven types of sketch curve were provided, including arc, ellipse, polygon, B-spline curve and so on. Using of graphic generation algorithm, primitives can be quickly generated by interactive mouse operations; solid modeling functionality is the most important part of the geometric modeling, which generates the basic elements of in order to achieve a variety of parametric modeling methods of a common three-dimensional solid model; particular, the complete expression of rectangular and cylindrical topology provided support for the subsequent meshing analysis; realistic graphics processing focus on solving the system illumination and visualization of material objects,7position adjustable light sources and20kinds of predefined material properties are achieved, and thus enhancing the realistic of geometric models in the scene of the CAD system.