Indirect diffuse and glossy illumination on the GPU

This paper presents a fast approximation method to obtain the indirect diffuse or glossy reflection on a dynamic object, caused by a diffuse or a moderately glossy environment. Instead of tracing rays to find the incoming illumination, we look up the indirect illumination from a cube map rendered from the reference point that is in the vicinity of the object. However, to cope with the difference between the incoming illumination of the reference point and of the shaded points, we apply a correction that uses geometric information also stored in cube map texels. This geometric information is the distance between the reference point and the surface visible from a cube map texel. The method computes indirect illumination although approximately, but providing very pleasing visual quality. The method suits very well to the GPU architecture, and can render these effects interactively. The primary application area of the proposed method is the introduction of diffuse and specular inter-reflections in games.