Dynamic scan-converted images with a frame buffer display device

A color interactive display system which produces images of three-dimensional polygons and labels on a frame buffer display device is being developed. The entire image is scan converted and written into the frame buffer whenever it is modified. Since an entire image cannot be written into the frame buffer faster than 4.6 frames per second for the particular device chosen, an illusion of continuous motion cannot be supported. However, a rate of 3 frames per second has been found sufficient to provide feedback to continuous user input. In order to achieve this frame rate for a reasonably complex picture, the display device has been microprogrammed to accept run length encoded data and text, and the instruction set of the computer has been extended by microprogramming special-purpose instructions which perform visible surface calculations. These microprograms currently can process a scene which consists of up to 170 polygons at 3 frames per second.