Volumetric path tracing
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Volumetric path tracing is a method for rendering images in computer graphics which was first introduced by Lafortune and Willems[1]. This method enhances the rendering of the lighting in a scene by extending the path tracing method with the effect of light scattering. It is used for photorealistic effects of participating media like fire, explosions, smoke, clouds, fog or soft shadows.
As in the path tracing method a ray gets followed backwards, beginning from the eye on, until reaching the light source. In volumetric path tracing scatter events can occur while these process. When the light path hits the surfaces a special amount of it gets scattered in the media[2].
Algorithm
The algorithm bases on the volumetric rendering equation[3], which extends the rendering equation with a scattering term. In volumetric path tracing a distance between the ray and the surface gets sampled and compared with the distance of the nearest intersection of the ray with the surface. If the sampled distance is smaller, a scatter event occurs. In that case the path gets evaluated and traced from the scatter point in the media, not from the surface point on which it falls. The rest of the procedure continues the same, until reaching the light source[4].
References
- ^ Lafortune, Eric P; Willems, Yves (June 1996). "Rendering participating media with bidirectional path tracing" (PDF). Proceedings of Rendering Techniques'96: 91–100.
- ^ Skånberg, Robin (January 2015). "Evaluation of Visual Parameters in Volumetric Path Tracing" (PDF). Department of Science and Technology, Linköping University: 20-22.
{{cite journal}}: Cite journal requires|journal=(help) - ^ Chandrasekhar, Subrahmanyan (1950). "Radiative transfer". Quarterly Journal of the Royal Meteorological Society. 76. John Wiley & Sons, Ltd. doi:10.1002/qj.49707633016. ISSN 1477-870X.
- ^ Kulla, Christopher; Fajardo, Marcos (June 2012). "Importance Sampling Techniques for Path Tracing in Participating Media". Comp. Graph. Forum. 31. John Wiley \& Sons, Inc.: 1519--1528. doi:10.1111/j.1467-8659.2012.03148.x. ISSN 0167-7055.