A Practical Analytic Model for the Radiosity of Translucent Scenes

a) b) c) Figure 1: Inter-reflection and subsurface scattering are closely intertwined for scenes with translucent objects. The main contribution of this work is an analytic model of combining diffuse inter-reflection and subsurface scattering (see Figure 2). One bounce of specularities are added in a separate pass. a) Two translucent horses (63k polygons) illuminated by a point light source. The three zoomed-in regions show that our method can capture both global illumination effects. b) The missing light transport component if only subsurface scattering is simulated. c) The same mesh rendered with a different lighting and viewing position. Our model supports interactive rendering of moving camera, scene relighting, and changing translucencies. 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 interreflections 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