A Lixel for every Pixel

Abstract

Shadow mapping is a very useful tool for generating shadows in many real-time rendering settings and is even used in some off-line renderers. One of the difficulties when using a shadow map is obtaining a sufficiently dense sampling on shadowed surfaces to minimize shadow aliasing. Endlessly upping the light-image resolution is not always a viable option. In this paper we describe a shadow mapping technique that guarantees, that over a small number of chosen planes of interest (such as a floor and a wall), the shadow map is, in fact, perfectly sampled, ie. for each pixel in the viewer camera, there will be exactly one lixel in the shadow map that samples the exact same geometric point.