A practical analytic model for the radiosity of translucent scenes

Light propagation in scenes with translucent objects is hard to model efficiently for interactive applications. The inter-reflections between objects and their environments and the subsurface scattering through the materials intertwine to produce visual effects like color bleeding, light glows and soft shading. Monte-Carlo based approaches have demonstrated impressive results but are computationally expensive, and faster approaches model either only inter-reflections or only subsurface scattering. In this paper, we present a simple analytic model that combines diffuse inter-reflections and isotropic subsurface scattering. Our approach extends the classical work in radiosity by including a subsurface scattering matrix that operates in conjunction with the traditional form-factor matrix. This subsurface scattering matrix can be constructed using analytic, measurement-based or simulation-based models and can capture both homogeneous and heterogeneous translucencies. Using a fast iterative solution to radiosity, we demonstrate scene relighting and dynamically varying object translucencies at near interactive rates.