Segmented ray casting for data parallel volume rendering

Interactive volume rendering is important to the timely analysis of three-dimensional data, but workstations take seconds to minutes to render data sets of a few megabytes. We have developed a parallel ray-casting technique, called Segmented Ray Casting, which can render a 128×128×128 data set at 2-3 frames per second on a 4K processor DECmpp 1200/Sx Model 100. Pixel values in the image plane are computed by casting rays through the volume data. The rays are segmented based on the intersection with the data sublocks in the processors. Each processor computes the color and opacity of the ray segments which pass through its subblock, which are then sent to the appropriate processor for composition with other segment values. Unlike other data-parallel volume renderers, Segmented Ray Casting does not require the transposition of volume data between processors at any time, nor does it suffer from resampling artifacts due to shearing