An Illumination Model for a Skin Layer Bounded by Rough Surfaces
In this paper we present a novel illumination model that takes into account multiple anisotropic scattering in a layer bounded by two rough surfaces. We compute the model by a discrete-ordinate solution of the equation of radiative transfer. This approach is orders of magnitude faster than a Monte Carlo simulation and does not suffer from any noisy artifacts. By fitting low order splines to our results we are able to build analytical shaders. This is highly desirable since animators typically want to texture map the parameters of such a shader for higher realism. We apply our model to the important problem of rendering human skin. Our model does not seem to have appeared before in the optics literature. Most previous models did not handle rough surfaces at the skin’s boundary. Also we introduce a simple analytical bidirectional transmittance distribution function (BTDF) for an isotropic rough surface by generalizing the Cook-Torrance model.
KeywordsRadiative Transfer Phase Function Skin Layer Global Illumination Cosine Series
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- 2.M. Born and E. Wolf. Principles of Optics. Sixth (corrected) Edition. Cambridge University Press, Cambridge, U.K., 1997.Google Scholar
- 3.S. Chandrasekhar. Radiative Transfer. Dover, New York, 1960.Google Scholar
- 5.P. Hanrahan and W. Krueger. Reflection from Layered Surfaces due to Subsurface Scattering. In Proceedings of SIGGRAPH ’93, pages 165–174. Addison-Wesley Publishing Company, August 1993.Google Scholar
- 7.X. D. He. Physically-Based Modelsfor the Reflection, Transmission and Subsurface Scattering of Light by Smooth and Rough Surfaces, with Applications to Realistic Image Synthesis. PhD thesis, Cornell University, Ithaca, New York, 1993.Google Scholar
- 8.H. W. Jensen, S. R. Marschner, M. Levoy, and P. Hanrahan. A Practical Model for Subsurface Light Transport. In Computer Graphics Proceedings, Annual Conference Series, 2001, page (to appear), August 2001.Google Scholar
- 11.E. P. F. Lafortune, S-C. Foo, K. E. Torrance, and D. P. Greenberg. Non-Linear Approximation of Reflectance Functions. In Computer Graphics Proceedings, Annual Conference Series, 1997, pages 117–126, August 1997.Google Scholar
- 12.E. Languénou, K. Bouatouch, and M. Chelle. Global illumination in presence of participating media with general properties. In Proceedings of the 5th Eurographics Workshop on Rendering, pages 69–85, Darmstadt, Germany, June 1994.Google Scholar
- 13.S. R. Marschner, S. H. Westin, E. P. F. Lafortune, K. E. Torrance, and D. P. Greenberg. Image-based brdf measurement including human skin. Eurographics Workshop on Rendering, 1999.Google Scholar
- 14.N. Max. Efficient light propagation for multiple anisotropic volume scattering. In Proceedings of the 5th Eurographics Workshop on Rendering, pages 87–104, Darmstadt, Germany, June 1994.Google Scholar
- 17.NETLIB. The code is publicly available from http://netlib.org.Google Scholar
- 18.M. Pharr and P. Hanrahan. Monte Carlo Evaluation of Non-Linear Scattering Equations for Subsurface Reflection. In Computer Graphics Proceedings, Annual Conference Series, 2000, pages 75–84, July 2000.Google Scholar