Improved Half Vector Space Light Transport

• Published in: Computer graphics forum Vol. 34; no. 4; pp. 65 - 74
• Main Authors: Hanika, Johannes, Kaplanyan, Anton, Dachsbacher, Carsten
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell Publishing Ltd 01.07.2015
• Subjects: Categories and Subject Descriptors (according to ACM CCS); Computer graphics; Differentials; Exploration; I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism-Raytracing; Light; Mathematical analysis; Perturbation methods; Strategy; Studies; Transport; Vector space; Vector spaces; Vectors (mathematics); United States > US
• ISSN: 0167-7055; 1467-8659
• DOI: 10.1111/cgf.12679

In this paper, we present improvements to half vector space light transport (HSLT) [KHD14], which make this approach more practical, robust for difficult input geometry, and faster. Our first contribution is the computation of half vector space ray differentials in a different domain than the original work. This enables a more uniform stratification over the image plane during Markov chain exploration. Furthermore, we introduce a new multi chain perturbation in half vector space, which, if combined appropriately with half vector perturbation, makes the mutation strategy both more robust to geometric configurations with fine displacements and faster due to reduced number of ray casts. We provide and analyze the results of improved HSLT and discuss possible applications of our new half vector ray differentials.