True Impostors

True Impostors offers an efficient method for adding a large number of simple models to any scene without having to render a large number of polygons. The technique utilizes modern shading hardware to perform ray casting into texture defined volumes. To achieve this, a virtual screen is set up in texture space for each impostor and inherits the same camera dependent orientation as the impostor. Each pixel on the impostor corresponds to a point on its virtual screen. By casting the viewing ray from this point into our texture defined volumes, the correct color for the target pixel can be found. The technique supports self-shadowing on models, reflection, refraction, a simple animation scheme, and an efficient method for finding distances through volumes.