Development And Improvement Research On Several Basal Algorithms Of Computer Graphics

Clipping and line-generating are two of the fundamental problems in computer graphics, and are also basis of other important problems. After several decades discussion and exploriation in clipping and line-generating, present algorithms are becoming better and better. But some of them are not perfect. What's more, research on 3-d clipping and 3-d line-generating is very little. It should be of great significance if improvement on 2-d algorithms and 3-d clipping and line-generating algorithms become reality.First, encoding technology based on window transformation and a new quick calculating of the intersections between the lines and the spherical surface are discussed. Based on first encoding technology, the second encoding technology is analyzed deep in theory by calculating effects of second encoding technology when rectangle window is circumgyrated different angle, so we can select appropriate angle according to actual conditions in order to get optimal effect. At one time the second encoding technology is developed from retangle window to circle window, from line clipping to polygon clipping and from 2-d clipping to 3-d clipping.Second, after limitations of present algorithms are analyzed, two improved clipping algorithms of polygon against rectangle window and line against polygon window are presented. By constructing the list of vertices of polygon and intersecting points between polygon and rectangle, the list of vertices of rectangle and between polygon and rectangle, the list of incoming points and the list of outcoming points, the problem that how to confirm close clipped area edge is solved. At the same time, the second encoding technology is developed from line clipping to polygon clipping so that the speed of algorithm is increased. The new line against polygon window clipping algorithm which makes full use of two judgement conditions to confirm noneffective intersections between the lines and the polygon edges can only calculate the effective intersections and increases the efficiency of the clipping.Third, a new 3-d clipping algorithm of line against spherical surface window is introduced for the first time. In the new algorithm, spherical surface window is discussed and 3-d line is divided into two kinds according to comparing the distance from sphere center to line with the radius of sphere. At the same time, the second encoding technology is developed to 3-d clipping and the 3-d encoding technology presented in this paper is characteristic, that is, by projecting 3-d line to 2-d plane we still use 2-d encoding technology in 3-d clipping to increase the speed of clipping.At last, a 3-d line-generating algorithm which makes full use of the projections on the 2-d plane and the symmetry, direction and continuity of the line is presented.