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.
다면체의 투시도를 컴퓨터에 의해 그릴 때는 입체의 특성에 따라 적합한 algorithm이 적용된다. 일반적으로 입체물이 설정되어진 절대좌표 상에서 각 면들의 가리워진 부분을 계산하는 object-space algorithm과 화면의 좌표상에서 투시도의 각 점의 위치를 구해 내는 image-space algorithm이 있다. 입체물이 복잡하지 않을 경우에는 object-space algorithm이 보다 효율적이며 비교적 빠른 시간 내에 입체물의 완전한 투시도를 얻을 수 있다.
본 논문에서는 object-space 상에서 완전히 가리워진 면을 찾아 미리 display file에서 제외한 후 완전히 보이는 면과 부분적으로 보이는 면들만 나타나 있는 image-space 상에서 면들의 가리워진 부분을 모두 찾아낸다.
