Interactive refraction on complex static geometry using spherical harmonics

TL;DR: A method to achieve realistic and interactive refractive effects through complex static geometry through complexstatic geometry is proposed, which relies on an offline step where many light paths through the object are pre-evaluated.

Abstract: Accurate refraction, thanks to raytracing, has always been a popular effect in computer graphics imagery. However, its use has been severely hindered in interactive rendering due to the lack of efficient and realistic techniques geared toward polygon oriented rendering.In this paper, a method to achieve realistic and interactive refractive effects through complex static geometry is proposed. It relies on an offline step where many light paths through the object are pre-evaluated. During rendering, these precomputed paths are used to provide approximations of actual refracted paths through the geometry, enabling further sampling of an environment map. Light paths valuable information, namely final output direction when leaving refractive object, is compressed using frequency domain based spherical harmonics. The matching decompression procedure, entirely offloaded onto graphics hardware, is handled at interactive speed.