Real-time spherical harmonics based subsurface scattering

In this paper we present an algorithm for a subsurface scattering simulation (SHSS) based on spherical harmonics. The approach has a physical basis. As we focus on specifying an algorithm suitable for commercial games, it contains simplifications designed for real-time calculations. Spherical harmonics (SH) functions were used to encode the thickness of an object in every possible direction for each vertex of a graphical model. The information about the thickness of an object is the basis for a simulation of light absorption. The starting point of our approach was the Green method [3], where the thickness is calculated by a shadow casting algorithm. In our technique the model volume is encoded by spherical harmonics similarly to the Precomputed Radiance Transfer where the SH are used to encode the values of a transfer function. The quality of our approach is presented in comparison with the other algorithms.