A Volumetric Approach to Rendering Microgeometry Using PRT

This paper introduces Precomputed Radiance Transfer (PRT) to shell textures in the context of rendering microgeometry. PRT is a method which allows static objects to have global illumination effects such as self shadowing and soft shadows while being rendered in real-time. This is done by representing the object’s spherical ’light transfer function,’ which captures how the object translates irradiance into radiant emittance, in a spherical/zonal harmonic basis in order to allow approximate illumination in arbitrary lighting environments. Shell textures is a technique for rendering complex surface geometry in real-time through the use of concentric 3D rings or shells around a model. The shells are transparent everywhere except at the intersection of the shell and the microgeometry that is being rendered. We novelly combine these two techniques to render realistic microgeometry with global lighting effects at real-time frame rates.