Progressive virtual beam lights

1Disney Research Zürich 2Karlsruhe Institute of Technology 3Université de Montréal

In Computer Graphics Forum (Proceedings of EGSR), 2012
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Indirect illumination on surfaces and in the medium. Our method (right) significantly reduces singularity artifacts compared to the virtual ray lights method (left). We effectively eliminate singularities in four indirect light transport paths (bottom) using novel importance sampling schemes and a new lighting primitive compatible with progressive rendering.
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Abstract

A recent technique that forms virtual ray lights (VRLs) from path segments in media, reduces the artifacts common to VPL approaches in participating media, however, distracting singularities still remain. We present Virtual Beam Lights (VBLs), a progressive many-lights algorithm for rendering complex indirect transport paths in, from, and to media. VBLs are efficient and can handle heterogeneous media, anisotropic scattering, and moderately glossy surfaces, while provably converging to ground truth. We inflate ray lights into beam lights with finite thicknesses to eliminate the remaining singularities. Furthermore, we devise several practical schemes for importance sampling the various transport contributions between camera rays, light rays, and surface points. VBLs produce artifact-free images faster than VRLs, especially when glossy surfaces and/or anisotropic phase functions are present. Lastly, we employ a progressive thickness reduction scheme for VBLs in order to render results that converge to ground truth.

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Jan Novák, Derek Nowrouzezahrai, Carsten Dachsbacher, Wojciech Jarosz. Progressive virtual beam lights. Computer Graphics Forum (Proceedings of EGSR), 31(4), June 2012. 
@article{novak12vbls,
    author   = {Nov\'ak, Jan and Nowrouzezahrai, Derek and Dachsbacher, Carsten and Jarosz, Wojciech},
    title    = {Progressive Virtual Beam Lights},
    journal  = {Computer Graphics Forum (Proceedings of EGSR)},
    volume   = {31},
    number   = {4},
    month    = jun,
    year     = {2012},
    doi      = {10/gfzndw},
    keywords = {photon beams, photon mapping, final gather, participating media, VPL, virtual point lights, VSL,
                virtual spherical lights, indirect illumination, weak singularity}
}
© The Author(s). This is the author's version of the work. It is posted here by permission of The Eurographics Association for your personal use. Not for redistribution. The definitive version is available at diglib.eg.org.