Lightcuts

I was browsing through some of the papers that have been accepted for SIGGRAPH over the last few years when I stumbled across one from Bruce Walter at Cornell about lightcuts.  It appeared 2 years ago but has been revised and extended since.

The basic idea of ”lightcutting” is to take the radiance equation:

(which calculates the radiance  of a set of point light sources  caused by their direct illumination at a surface point viewed from the direction ) and reduce the cost of the solution (which is currently linear) to a sub-linear scalable one.  To do this it introduces the idea of partitioning the lights into clusters using a light tree (effectively a binary tree).  Once introduced the paper also looks at introducing other types of illumination into the lightcuts frameword (such as HDR environment maps, area lights and such).

It also goes on to explore reconstruction cuts whcich exploit spatial coherence to reduce average shading costs.

The results seem brilliant, it can reduce the cost needed to compute illumination in pretty complex scenes while still maintaining the detail of the image.

I’d really love to try and implement this in a rendering engine (pbrt? blender?), the only problem is finding the time to do it….