Back-face culling applied to collision detection of polyhedra

Back-face culling is a preprocessing technique used in computer graphics to speed up the rendering of polyhedra. In this paper we show how this technique can be modified to reduce unnecessary checking of boundary elements in collison detection for a physical-based simulation and animation systems. At each time step, we determine a priori which faces cannot be part of the contact between two polyhedra and thus can be culled. In the computer graphics technique, the normal vector of a polygon is compared with the view direction. Here, the normal is compared to one or possibly several relative-velocity vectors, and the face is culled when its motion is in the opposite direction of the normal vector. We also give an algorithm that takes linear time in terms of the number of faces, and on the average eliminates half of the polygons. Owing to its low computational overhead, when it is used as a front end to a collision detection system, a noticeable improvement in performance can be achieved.