PARM: Data Structure for Efficient Volume Ray Casting

Abstract

We propose a new data structure to accelerate the color computation step of CPU-based volume ray casting. To ensure interactive frame rates on a PC platform, we store interpolated scalar value and gradient vector required for color computation step in volume ray casting. However, it is difficult to store those two values in preprocessing step because sample points can lie in arbitrary position in a cell. Therefore, after determining candidate cells that contribute to the final images, we partition each candidate cell into several sub-cells. Then, we store trilinearly interpolated scalar value and an index of encoded gradient vector for each sub-cell. Because the information that requires time-consuming computations is already stored in our data structure, color values are determined without further computations.