Path-Space Manipulation of Physically-Based Light Transport

Thorsten-W. Schmidt, Jan Novák, Johannes Meng, Anton Kaplanyan, Tim Reiner, Derek Nowrouzezahrai, and Carsten Dachsbacher

ACM Transactions on Graphics (Proceedings of SIGGRAPH 2013), vol. 32, no. 4

Transport manipulation in the GARAGE scene. Before/after close-ups (right): removing indirect highlights caused by the car, re-directing sunlight after it refracts through the windows, moving and rotating a glossy interreflection, and altering the mirror reflection.

abstract

Industry-quality content creation relies on tools for lighting artists to quickly prototype, iterate, and refine final renders. As industry-leading studios quickly adopt physically-based rendering (PBR) across their art generation pipelines, many existing tools have become unsuitable as they address only simple effects without considering underlying PBR concepts and constraints. We present a novel light transport manipulation technique that operates directly on path-space solutions of the rendering equation. We expose intuitive direct and indirect manipulation approaches to edit complex effects such as (multi-refracted) caustics, diffuse and glossy indirect bounces, and direct/indirect shadows. With our sketch- and object-space selection, all built atop a parameterized regular expression engine, artists can search and isolate shading effects to inspect and edit. We classify and filter paths on the fly and visualize the selected transport phenomena. We survey artists who used our tool to manipulate complex phenomena on both static and animated scenes.

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bibtex

@article{Schmidt2013PSM,
    author      = {Schmidt, Thorsten-Walther and Nov\'{a}k, Jan and Meng, Johannes and Kaplanyan, Anton S. and Reiner, Tim and Nowrouzezahrai, Derek and Dachsbacher, Carsten},
    title       = {Path-space Manipulation of Physically-based Light Transport},
    journal     = {ACM Transactions on Graphics (Proceedings of ACM SIGGRAPH 2013)},
    volume      = {32},
    number      = {4},
    month       = jul,
    year        = {2013},
    issn        = {0730-0301},
    pages       = {129:1--129:11},
    articleno   = {129},
    publisher   = {ACM},
    address     = {New York, NY, USA},
    doi         = {10.1145/2461912.2461980},
    acmid       = {2461980},
}