Efficient self-shadowed radiosity normal mapping

In Valve's Source graphics engine, bump mapping is combined with precomputed radiosity lighting to provide realistic surface illumination. When bump map data is derived from geometric descriptions of surface detail (such as height maps), only the lighting effects caused by the surface orientation are preserved. The significant lighting cues due to lighting occlusion by surface details are lost. While it is common to use another texture channel to hold an "ambient occlusion" field, this only provides a darkening effect which is independent of the direction from which the surface is being lit and requires an auxiliary channel of data. In this chapter, we present a modification to the Radiosity Normal Mapping system that we have described in this course in the past. This modification provides a directional occlusion function to the bump maps, which requires no additional texture memory and is faster than our previous non-shadowing solution.