Monday, June 16, 2014

Subsurface Scattering Updates

I've been spending time updating my subsurface scattering algorithm to incorporate more recent state of the art research. The original papers I was using were written over 10 years ago and since then many improvements have been made to classical diffusion theory. Incorporating these updates have definitely been worthwhile.

My current algorithm combines techniques from four different papers:

1) I use the single-scattering term as described in the original SSS paper by Jensen:

2) For multi-scattering, I make use of a hierarchical irradiance-caching point cloud as described here:

3) I use some improved definitions of several terms as described in the following paper. These include improved boundary condition and diffusion coefficient terms amongst others.

4) Finally, I replace the standard dipole-diffusion algorithm with a hybrid extended-dipole source / Monte Carlo simulation as described here:

You can see several of my newest images below. In addition to the hue of the materials matching reality more closely, increasing the translucency of the material does not cause the model to brighten up and "glow" like it did before - instead the illumination simply becomes more blurred and soft.

Jade Dragon

Marble Statue

Scattering and Absorption Coefficients cut by two each

Scattering and Absorption Coefficients cut by four each

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