This technical report provides a description and comparison of classical and improved diffusion theory as used for rendering subsurface scattering in computer graphics. We discuss the searchlight problem and describe the diffusion equation and Green's functions of each diffusion theory. We discuss the commonly used single-depth approximation leading to the diffusion dipole and elaborate on its connection to the desired extended-source function.
@techreport{habel13cid,
author = {Habel, Ralf and Christensen, Per H. and Jarosz, Wojciech},
title = {Classical and Improved Diffusion Theory for Subsurface Scattering},
institution = {Disney Research Z\"urich},
year = {2013},
month = jun,
keywords = {subsurface scattering, dipole, sss, photon beams, quantized diffusion, BSSRDF, translucent,
diffusion theory, Grosjean}
}