SURFACE SHADING IN THE CUBERILLE ENVIRONMENT.

Medical imaging devices (such as computed tomography scanners) often produce data on real objects by assigning values to small, rectangular, abutting volumes of space. The cuberille model, in which space is dissected by three mutually orthogonal sets of parallel planes, represents such data quite well. Segmentation of the cuberille into object and background, followed by boundary detection, gives an approximation (consisting of faces in the cuberille) to the real object's surface. In order to render the detected boundary surface on a display screen so that details are retained but the appearance of a real object (as opposed to one consisting of cubes) is provided, the authors propose a number of shading methods. Their performance with existing methods using medical and artificial objects is compared. Overall, they find the new normal-based contextual shading method superior to the others they have tested; it provides images practically indistinguishable from those provided by the Phong shading method at significantly reduced cost.