Progressive Virtual Beam Lights

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.

@article{Novak2012VBL,
    author = {Jan Nov{\'a}k and Derek Nowrouzezahrai and Carsten Dachsbacher and Wojciech Jarosz},
    title = {Progressive Virtual Beam Lights},
    journal = {Computer Graphics Forum (Proceedings of EGSR 2012)},
    volume = {31},
    number = {4},
    month = jun,
    year = {2012},
    pages = {1407--1413},
    publisher = {John Wiley \& Sons, Inc.},
    address = {New York, NY, USA},
    keywords = {photon beams, photon mapping, final gather, participating media, VPL, virtual point lights, VSL, virtual spherical lights, indirect illumination, weak singularity}
}