CMU VASC Talk: Shedding Light on Scattering

Srinivas Narasimhan
CMU
Monday, September 19, 2005

Abstract: This is really two talks combined into one. The vision part will appear in ICCV'05 and the graphics part appeared in Siggraph'05.

In the first half, I will explore the effects of active illumination in scattering media like underwater, atmosphere and fluids. Active illumination is often used by underwater vehicles and divers to explore and inspect underwater scenes, automotive manufacturers in designing headlights to see through fog and even microscopic imaging of biological tissues and organisms. In all these cases, the appearances of the scenes are corrupted due to scattering by the medium and hence, traditional structured light approaches fail completely. I will present physics based methods to make structured light techniques successful in scattering media. In addition, I will show surprising results that could not have been computed using traditional methods even in clear air (depth from photometric stereo, reconstructing mirrors and seeing through milk).

In the second half, I will show how to render scattering effects in real-time, considering even more complex near-field lighting from point sources. The core result here is that the expensive integral of a 5D scattering function that needs to be computed for every viewing and surface illumination direction is factored into a product of an analytic function and a lookup of a 2D pre-computed function. This allows us to use standard textures and graphics hardware to render realistic effects at around 20-30fps. The algorithm is very simple to implement, can be used extensively in games for which third-party developers have already created Maya plugins of our algorithms.