The best known prior art systems for generating fully occulted real time 3D images is the Z-buffer or depth buffer image precision algorithm. This may be implemented in either software or hardware and is used in systems produced by companies such as Silicon Graphics, Evens and Sutherland, and Hewlett Packard.
The Z-buffer algorithm requires a frame buffer in which colour values are stored for each pixel in an image. In addition to this it requires a Z-buffer with an entry for each pixel. In this a Z value (depth value) is stored for each pixel. To generate a 3D representation polygons, such as triangles, are rendered into the frame buffer in arbitrary order. During scan conversion of the polygon if a point on a polygon is no further from the viewer than the point already in the buffer for that pixel then the new point's colour and Z value replace the old values. No presorting is necessary and no object to object comparisons are required.
Z-buffer type systems require a high level of integration and performance and are very expensive. It is necessary to use a high performance frame buffer and Z-buffer if real time performance is to be achieved.