Explain about Franklin Algorithm
We mentioned how the number of possible comparisons of polygons grows as the square of the number of polygons in the scene. Many of the hidden-surface algorithms exhibit this behaviour and have serious performance problems on complex scenes. Franklin developed an approach which gives linear time behaviour for most scenes. This is done by overlaying a grid of cells on the scene (similar to Warnocks approach, only these cells Visual Realism are not subdivided). The size of the cells is on the order of the size of an edge in the scene. At each cell the algorithm looks for a covering face and determines which edges are in front of this face. It then computes the intersections of these edges and determines their visibility. The idea is that as objects are added to the scene and the number of polygons increases, the new objects will either be hidden by objects already in the scene or will hide other objects in the scene. While the number of objects increases, the complexity of the final scene (after hidden portions are removed) does not increase. By considering only the edges in front of the covering face for a cell, the algorithm considers only the edges likely to be in the final image. Although the total number of edges may increase, this increase occurs, for the most part, behind the covering faces, and the number of edges in front will remain small.