SIGGRAPH 2003: Scattering and Reflection Measurement papers

I came in half way through this paper session, because I had started the day in Fluids and Smoke. The two papers that I witnessed in this session concentrated on lighting and reflections in human tissues and hair, and both had some interesting insights.

Image-based Skin Color Simulation by Extracting Hemoglobin and Melanin Information

Wow... big title. The researchers who presented this paper are all from Japan and have been researching the realistic simulation of skin colors for some time. In particular, the work has both a cosmetic component (to be used in simulating tanning and other operations) and a medical diagnostic component.

Their key observation is that skin color can be quite accurately simulated by splitting out the effects of melanin in the epidermis and hemoglobin in the dermis. Melanin contributes the contrast and the tanning colors, while the hemoglobin provides the rich reds.

Although that information is useful, the true interest in this paper is because they have determined a cheap and effective mechanism for determining this information using a polarizing filter, digital camera, and some analysis algorithms. The results were quite amazing, allowing the researchers to "dial up" tan levels and blood simulations from pale to what they referred to as drunk.

Beyond the uses for simulation, the team is also looking at the technique for diagnostic purposes by analyzing density of both melanin and hemoglobin to look for potential cancers and blood flow problems, respectively.

Light Scattering from Human Hair Fibers

The final paper in this section deals in great detail with the way that hair reflects light. Having relatively little knowledge in this area, I found the topic fascinating. The most important revelations were that a cross-section of human hair is elliptical, not circular, and varies by race; and that hair fibers are not smooth, they are instead scaled.

The implication is that hair is asymmetrical (because the scales have different normals depending on whether you are headed toward or away from the scalp), and that it creates a non-uniform scattered distribution of reflected light.

Extensive illustrations and simulations were covered, however they have not extended their work to deal efficiently with an entire head of hair.