X-Ray Casting: Fast Volume Visualization Using 2D Texture Mapping Techniques

An approach is described for approximating 3D volumetric rendering of medical data for use in surgical simulation. Our approach uses a two-step method we call X-Ray Casting. In the first step, rays are cast through the volume, and projected onto a 2D projection surface, producing a 2D texture map. In the second step, the resulting texture is rendered by mapping it onto semi-opaque geometry of the same shape as the projection surface. The first step is performed off-line and is view-independent, while the second step is done at interactive frame rates and is view-dependent. The rendering step takes less time than more traditional volumetric rendering techniques, while still providing reasonable realism for surgical simulation environments. In addition, the approach makes good use of the limited amount of fast texture memory present in many relatively low-cost, high-performance graphics workstations, compared with the large texture memory requirements of high-cost, real-time volumetric rendering systems. This paper reports on work in progress.