Rendering of Complex Materials for Driving Simulators

The visual realism of a virtual scene is very important for driving simulators. In real life, a scene is composed of complex materials (asphalt, vegetation, road mark...) interacting with light sources (sun, headlamps...). Our goal is to simulate such environments in real time under various weather conditions (dry or wet road). The lighting interaction cannot be simulated directly using standard lighting model implemented in graphic board (Phong shading). In this paper, we present a method for rendering complex materials with BTF (Bidirectional Texture Function). This method, which allows to view various and complex lighting phenomenon (such as interreflections, self-shadowing and masking effects), requires a long computation chain and uses a large data set (one or more gigabytes). The main steps of this method are exposed : BTF acquisition (both virtual and through measurement), data compression (a dedicated algorithm can achieve compressions rates above 2000:1), and real time implementation techniques using vertex and pixel shaders. We present our first results, applications and discuss about limitations and future works of this rendering technique.