Hidden surface elimination algorithm

Abstract

Computer graphics is much applied to man-computer interactive systems. It has been used as a tool that gives us most definite, explicit, and explicative solutions in real time, such that as drawing graphs corresponding to mathematical equations or geometrical figures and representing objects which are pre-designed in engineering, and so forth. Especially representation of three dimensional objects is one of the most interesting fields in computer graphics. In the thesis some problems which will be produced when we draw a perspective view of an object by computer are considered especially for reducing the number of computations. In this paper the algorithm deals with polyhedra, that is, objects whose surfaces are a collection of some polygons. Also it will be extended to general objects, if their smooth surfaces are represented by a set of small interpolating polygons. Thus we can get the perspective view of an object as the wire-framed picture by drawing all their visible edges. Faces of a polyhedron can be divided into three classes;completely invisible faces, partially visible faces, and completely visible faces. The algorithm eliminates invisible parts step-by-step. First, completely invisible faces are eliminated, and next, it detects partially visible faces and determines which parts of the faces are visible. The number of computations can be reduced in testing edges since the edges of completely invisible faces are excluded before testing.