Three-dimensional Solid Surface Modeling Technology Research And Software Development

CAD/CAM originated in aero industry, and is closely relative to free curves and surfaces from the beginning for the airplane figures' much free surfaces. Nowadays, the construction module of free curves and surfaces is still the core one of the key parts in CAD/CAM. The technique of free curves and surfaces can not only describe elementary curves and surfaces, but also precisely describe the curves and surfaces in free. The free curves and surfaces are not able to be expressly described by the Descriptive Geometry and Mechanism. Furthermore, computer can calculate and dispose the mathematic model of free curves and surfaces, and get a large number of points and information concerned which is the base of the later treatment such as numerical control, objective analysis etc. The designer can adjust the part or whole of the curve or surface to make display and adjustment work at the same time. By the computer, the designer can get precisely curves and surfaces without the use of traditional ways to decrease the period of designation and production, increase the precision of manufacture, improve the harmony, and it is adaptable to the development of aero industry, automobile, mechanics and so on.In order to develop a 3D CAD software with perfect function, high efficiency and reliability, which also accords with the design habit of our engineers, a new 3D software that is JhSolid is developed by the Object-Oriented method. The program takes fully advantage of the functions provided by Parasolid and develops the computer means of the construction of spatial curves and surfaces under the Computer Aided Geometric Design theory, Graphical theory. And these means are creation & edit of NURBS curves in the plane, creation & edit of B-curve in the space, creation & edit of surfaces in the space. In the course of developing free curves and surfaces, the paper took much time to study the arithmetic of creation and edit of NURBS curve which was applied to the JhSolid system. The NURBS curve is treated as the standard ways. The arithmetic is de Casteljau's NURBS curve's method, the square boxes' method and adjusting weights' method and etc. In the chapter of surface creation, the paper mostly resolves the methods of surface defined in the square field, and especially studies the triangular surfaces. For instance, the paper develops the skinning surface with singular point which is not defined in the square field. The paper takes a try to develop the program of constructing triangular surfaces and HCT operation. In the chapter of surfaces edit, the paper introduces the idea which combines solid creation with surface edit, the idea makes full use of functions provided by Parasolid and the predominance of surface creation.It has verified that this program has succeeded in realizing above-mentioned functions, which prove the correctness and feasibility of this method.