Robust Diffuse Final Gathering on the GPU

This paper presents a method to obtain the approximate indirect diffuse 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 albeit approximately, but providing very pleasing visual quality. The method fits very well the GPU architecture, and can render these effects interactively. The primary application area of the proposed method is the introduction of diffuse interreflections in games.