The Aplication Of Surface Intersection At Highway Displays

Computer graphics is a new branch of science which developed rapidly in recent decades with the prospects of wider application . With the rapid development of computer ,it has been widely used in aviation, aerospace, automotive, electronics, civil engineering, etc,and to promote the developmeng of this discipline quickly. In today's Computer-aided design, Computer-aided manufacturing, Gomputer graphics,etc, Geometric modeling system is one of their core,there are mang represents in Geometric modeling system,border represent is the most important one.In order to express the boundary well, surface intersection must be done frequently ,so surface intersection is widly used in Computer-aided design, Computer-aided manufacturing , Gomputer graphics, Collections is the prerequisite of collections computing , is the key of system stability. The intersection between Surfaces is achieved mainly through the intersection between parametric surfaces . Nowadays, There are three typical algorithm in the intersection of parameters surfaces : grid method, tracking method and discrete subdivision method. In this paper, combine the grid method and the discrete subdivision method so that try to make up for their lacks , hoping to achieve a better intersection result. Application of the mathod at the three-dimensional display of highway acquires the desired effect. In this article, firstly, in accordance with changes in terrain conditions status , divided the big surface into many small surface, in relatively flat topography the surface is divided roughly, in relatively rough topography the surface is divided fine, lastly, the small surface is approximated by triangular surface respectly.The key questions that need to be resolved are aware of a surface is made up of a number of triangular surface then how to gain their intersection lines which devided the surface triangular into two sections and get rid of the hiding sections of the surface and form a new surface which maintance the same data structure. Surface intersection eventually comes down to the intersection of two triangles. There are different triangle-intersection algorithm . In this paper, combine the parameters method of surface intersection and the location of two triangles to do the intersection of the surface ,so that make up the problems of too mang computation. As for the removal of hiding surface in surface intersection process ,we use the usual two-dimensional ray method ,and extended the method to three-dimensional ray, and achieved the desired results.