A hardware stochastic interpolator for raster displays

Stochastic modeling has found uses so far mainly for expensive very realistic graphics display. The cost of rendering is not intrinsic to the technique, but mainly due to the high resolution and the sophisticated display techniques which accompany it. We describe here a basic tool for a less expensive approach to stochastic modeling which is designed for a more “down to earth” type of application, and brings the display of stochastic models nearer to real-time. A special purpose board for stochastic interpolation has been built, which can generate an array of up to 129×129 12 bit stochastic values to be used by the rest of the display system as a texture source, or for more elaborate algorithms. The board functions as a coprocessor in a traditional frame buffer system, and includes a micro-coded bit-slice processor, a multiplier, special hardware to generate uniformly distributed random numbers, memory to store a look-up table for random numbers with the required distribution, and two buffers for the resulting arrays. The current implementation generates values at less than 4 microseconds per point, and in conjunction with a standard graphics processor can display nearly 10000 stochastic points in real-time, or can update a full screen of stochastic values in less than one second. Illustrations are given of the output of the board and of pictures and animations generated with it.