Acceleration of ray-casting using 3-D distance transforms

This paper introduces a novel approach for speeding up the ray casting process commonly used in volume visualization methods. This new method called Ray Acceleration by Distance Coding (RADC) uses a 3-D distance transform to determine the minimum distance to the nearest interesting object; the implementation of a fast and accurate distance transform is described in detail. High distance values, typically found at off-center parts of the volume, cause many sample points to be skipped, thus significantly reducing the number of samples to be evaluated during the ray casting step. The minimum distance values that are encountered while traversing the volume can be used for the identification of rays that do not hit objects. Our experiments indicate that the RADC method can reduce the number of sample points by a factor between 5 and 20.