Monday, July 15, 2013

Spotted: Axis-aligned filtering for interactive physically-based diffuse indirect lighting

Interactive sampling using optix or similar, with interactive reconstruction, based on improved understanding of diffuse interreflection. 

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// published on ACM Transactions on Graphics (TOG)-Current Issue // visit site

Axis-aligned filtering for interactive physically-based diffuse indirect lighting

Soham Uday Mehta, Brandon Wang, Ravi Ramamoorthi, Fredo Durand

We introduce an algorithm for interactive rendering of physically-based global illumination, based on a novel frequency analysis of indirect lighting. Our method combines adaptive sampling by Monte Carlo ray or path tracing, using a standard GPU-accelerated raytracer, with real-time reconstruction of the resulting noisy images. Our theoretical analysis assumes diffuse indirect lighting, with general Lambertian and specular receivers. In practice, we demonstrate accurate interactive global illumination with diffuse and moderately glossy objects, at 1-3 fps. We show mathematically that indirect illumination is a structured signal in the Fourier domain, with inherent band-limiting due to the BRDF and geometry terms. We extend previous work on sheared and axis-aligned filtering for motion blur and shadows, to develop an image-space filtering method for interreflections.

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