1. A texture mapping system, comprising: memory for storing a parametric texture map, the parametric texture map having a plurality of texels, each of the texels defining a variable expression that defines a luminosity parameter as a function of light direction; and a texture map manager configured to perform a rotation of a texture defined by the parametric texture map, the texture map manager further configured to adjust the variable expression of at least one of the texels to compensate for the rotation.