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Dual Scattering for Hair

Dual scattering offers an extremely fast simulation of multiple scattering in hair. No parameter tweaking is necessary to achieve accurate results with arbitrary lighting conditions. In this figure, the path tracing reference takes several hours to compute, while by using dual scattering we can reduce this time to several minutes in our offline implementation or even real-time frame rates with our GPU implementation, which uses a similar approach to Deep Opacity Maps. Click on the image to enlarge.

Abstract

When rendering light colored hair, multiple fiber scattering is essential for the right perception of the overall hair color. In this context we present a novel technique to efficiently approximate multiple fiber scattering for a full head of human hair or a similar fiber based geometry. In contrast to previous ad-hoc approaches our method relies on the physically accurate concept of the Bidirectional Scattering Distribution Functions and gives physically plausible results. We show that the complex scattering effects can be approximated very well by using aggressive simplifications based on this theoretical model. When compared to unbiased Monte-Carlo path tracing, our approximations still preserve photo-realism in most settings but with rendering times at least two-orders of magnitude lower. Time and space complexity are much lower compared to photon mapping-based techniques and we can even achieve realistic results in real-time on a standard PC with consumer graphics hardware.

Comparing dual streaming to single scattering only and simpler/conventional non-physical techniques that require significant parameter tweaking and still fail to achieve the realism of dual scattering. Click on the image to enlarge.

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