Patent ID: 7355598

Claim:
A method for performing volume rendering, comprising: providing a digitized volumetric comprising a plurality of intensities corresponding to a domain of voxels in a 3-dimensional space and a color/alpha channel lookup table; performing a pre-processing step, said preprocessing step comprising constructing a Reduced Path Octree data structure; generating a 2-D image by casting a ray from each pixel of the image into the volume; casting the ray through the Reduced Path Octree for a first pass to determine a threshold, wherein said first pass comprises visiting each first level node along said ray to determine a first pass extremal intensity value and the position of the node that contains the extremal value; casting the ray through the volumetric image for a second pass; visiting each level of the Reduced Path Octree node and determining the emptiness of nodes at each level during the advancing of the ray in the second pass; sampling along the ray inside only the non-empty region and skip the empty region; and determining a rendering value for the ray, wherein said rendering value is a second pass extremal value associated with a pixel from which said ray was cast.