“Interactive summed-area table generation for glossy environmental reflections”

There are many applications in computer graphics where spatially varying filters are useful. One example is the rendering of glossy re- flections. Unlike perfectly reflective materials, which only require a single radiance sample in the direction of the reflection vector, glossy materials require integration over a solid angle. Blurring by filtering the reflected image with a support dependent on the surface‘s BRDF can approximate this effect. This is currently done by pre-filtering off-line, which limits the technique to static environments. Crow [1984] introduced summed-area tables to enable more general texture filtering than was possible with mip maps. Once generated, a summed-area table provides a means to evaluate a spatially varying box filter with a constant number of texture reads.

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Kautz, J., Vazquez, P.-P., Heidrich, W., and Seidel, H.-P. 2000. A unified approach to prefiltered environment maps. In Eurographics Workshop on Rendering.