Paper Info
Title
Portal-masked environment map sampling
Abstract
We present a technique to efficiently importance sample distant, all-frequency illumination in indoor scenes. Standard environment sampling is inefficient in such cases since the distant lighting is typically only visible through small openings (e.g. windows). This visibility is often addressed by manually placing a portal around each window to direct samples towards the openings; however, uniformly sampling the portal (its area or solid angle) disregards the possibly high frequency environment map. We propose a new portal importance sampling technique which takes into account both the environment map and its visibility through the portal, drawing samples proportional to the product of the two. To make this practical, we propose a novel, portal-rectified reparametrization of the environment map with the key property that the visible region induced by a rectangular portal projects to an axis-aligned rectangle. This allows us to sample according to the desired product distribution at an arbitrary shading location using a single (precomputed) summed-area table per portal. Our technique is unbiased, relevant to many renderers, and can also be applied to rectangular light sources with directional emission profiles, enabling efficient rendering of non-diffuse light sources with soft shadows.
Year
DOI
Venue
2015
10.1111/cgf.12674
Computer Graphics Forum
Keywords
Field
DocType
Categories and Subject Descriptors (according to ACM CCS),I,3,7 [Computer Graphics]: Three-Dimensional Graphics and RealismRaytracing
Computer vision,Importance sampling,Visibility,Computer graphics (images),Ray tracing (graphics),Computer science,Rectangle,Artificial intelligence,Sampling (statistics),Rendering (computer graphics),Solid angle,Reflection mapping
Journal
Volume
Issue
ISSN
34
4
0167-7055
Citations 
PageRank 
References 
4
0.54
18
Authors
3
Name
Order
Citations
PageRank
Benedikt Bitterli1513.92
Jan Novák228617.42
Wojciech Jarosz3104160.39