Perturbed Normal Bump Mapping
This technique is very close to what is called True Bump Mapping. This technique is supported in DirectX V6.0 and is supported by the PVRSG hardware. All bump effects are possible with this technique.
This technique actually influences the light calculations, it uses the normal of the polygon, the light vector and the light color and intensity. The bump map used in the PowerVRSG hardware is a real height map meaning it is very easy and straightforward to use. Inside the chipset this height map is translated to a perturbation map based on the slope of the surface. This perturbation is used to change the normal of the polygon. This new perturbed normal is used in combination with the light source information to do a true light calculation. This results in very accurate light and shadow effects. These effects can be update easily by giving the new light position (only new vector needed).
Following figures show the changing of the light vector. All you need to know is that the perturbed light vector is used for the light calculations and this creates very accurate effects. There are several sample MPEGs available at www.powervr.com.
