We focus on rendering the effects of scattering in participating media like mist, fog or haze. While volumetric scattering is extremely difficult to simulate computationally, its qualitative effects are relatively simple, usually involving blurring, such as the glows around light sources. We focus on deriving novel analytic results, in particular a point spread function describing the glow around light sources, or the spreading of a beam through a medium. These can then be used to develop efficient rendering algorithms. We have demonstrated real-time rendering with the effects shown in the images above.
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| Publications |
We have so far derived two results, both making use of analytic point spread functions for efficient rendering of volumetric scattering. A third result, deriving an analytic solution to the radiative transport equations for multiple scattering is under review. In our first approach, we use analytic expressions for the spread of a beam due to multiple scattering in a participating medium. This can then be used in an efficient rendering algorithm for inhomogeneous media. In our second approach, which we believe to be a significant theoretical and practical contribution to real time rendering, we derive new analytic expressions for the airlight or glow around a light source due to single scattering. The results are expressed as a combination of an analytic function depending only on the physical parameters of the problem, and a purely numerical 2D lookup table, which can be precomputed and stored once. This enables efficient implementation on modern programmable graphics hardware. Furthermore, the approach can be extended to handle the effects of scattering on surface radiance and the effects of complex lighting and materials, which are often omitted even in numerical Monte Carlo methods, as being too expensive computationally.
Most recently, we have also shown how to acquire the scattering properties of a variety of substances by dilution in water to the single scattering regime. This represents the first database of volumetric scattering, which we hope will be analogous to databases of measured BRDFs and BTFs.
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A Practical Analytic Single Scattering Model for Real Time Rendering
Siggraph 05, pages 1040-1049 We develop an analytic airlight model by explicitly integrating the single scattering equations for light transport due to a point source in a homogeneous medium. Paper: PDF Video (74M) |
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Practical Rendering of Multiple Scattering
Effects in Participating Media
EGSR 04, pages 363-374 We use an expression for the spreading of a beam in a participating medium, and develop an efficient and general rendering algorithm Paper: PDF |
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Acquiring Scattering Properties of Participating Media by Dilution
SIGGRAPH 06, pages 1003-1012 We present a simple device and technique for robustly estimating the properties of a broad class of participating media that can be either (a) diluted in water such as juices or beverages, (b) dissolved in water such as powders and sugar/salt crystals, or (c) suspended in water, such as impurities. Paper: PDF |