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In Proceedings of Graphics Interface

Visibility sweeps for joint-hierarchical importance sampling of direct lighting for stochastic volume rendering

Thomas Kroes, Martin Eisemann, and Elmar Eisemann

We compute the product of approximated visibility and environment map lighting in a stochastic Monte Carlo volume renderer to steer a joint importance sampling of the direct lighting. Our proposed two-step approach is well suited for dynamic changes in visibility and lighting functions due to a fast sweeping-plane algorithm to estimate visibility. The insets show how our technique (blue) achieves faster convergence with less samples compared to a uniform sampling (red) and importance sampling of the environment map (yellow). Here, 64 samples per pixel have been used. The Manix data set consists of 512×512×460 voxels.

Physically-based light transport in heterogeneous volumetric data is computationally expensive because the rendering integral (particularly visibility) has to be stochastically solved. We present a visibility estimation method in concert with an importance-sampling technique for efficient and unbiased stochastic volume rendering. Our solution relies on a joint strategy, which involves the environmental illumination and visibility inside of the volume. A major contribution of our method is a fast sweeping-plane algorithm to progressively estimate partial occlusions at discrete locations, where we store the result using an octahedral representation. We then rely on a quadtree-based hierarchy to perform a joint importance sampling. Our technique is unbiased, requires little precomputation, is highly parallelizable, and is applicable to a various volume data sets, dynamic transfer functions, and changing environmental lighting.

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Paper preprint

Citation

Thomas Kroes, Martin Eisemann, and Elmar Eisemann, Visibility sweeps for joint-hierarchical importance sampling of direct lighting for stochastic volume rendering, In Proceedings of Graphics Interface, pp. 97–104, 2015.

BibTex

@inproceedings{bib:kroes:2015,
    author       = { Kroes, Thomas and Eisemann, Martin and Eisemann, Elmar },    
    title        = { Visibility sweeps for joint-hierarchical importance sampling of direct lighting for stochastic volume rendering },
    booktitle    = { In Proceedings of Graphics Interface },
    year         = { 2015 },
    pages        = { 97--104 },
    dblp         = { conf/graphicsinterface/KroesEE15 },
    url          = { https://publications.graphics.tudelft.nl/papers/273 },
}