Rendering human skin realistically poses the challenge of solving subsurface lighting sufficiently correct. This challenge is quite diffcult for skin due to its slight transluceny. This causes light entering the material to be scattered within and travel relatively long distances before exiting again. This distance then corresponds to more than a pixel's width of the final image. In this case the effect of subsurface scattering cannot be approximated with a simple BRDF like the Lambertian BRDF. Thus another way to ...
A lightmap, also known as irradiance map, is a two dimensional texture which is mapped to the static geometry of a scene. By storing irradiance at each texel's world space position, a lightmap lookup returns the precalculated radiance falling on a surface at that position. The advantage of such a precalculation is that global illumination can be solved correctly ahead of time and then applied very fast at run time. The generated lightmap however, is only valid as long as ...
