The Virtual Lighting Laboratory: Per-pixel Luminance Data Analysis Mehlika N. Inanici 1 , and Mojtaba Navvab 2 1 INTRODUCTION T he Virtual Lighting Laboratory (VLL) is an image based lighting analysis tool and methodology, which operates with physically-based High Dynamic Range (HDR) digital images. Through appropriate modeling, rendering, and image technology, physically based renderings and HDR Photographs can be used to extract per-pixel lighting information. Extraction of per-pixel luminance data is done by converting the RGB values in each pixel of HDR imagery (that is, an RGBE image, also known as hdr) into CIE XYZ data using the CIE 1931 Standard Colorimetric Observer Functions. A detailed documentation of the study can be found in (Inanici 2004). In VLL, per-pixel lighting data extracted from physically based renderings is processed through mathematical and statistical operations to perform lighting analysis with detail, flexibility and rigor that may be infeasible or impossible with the traditional lighting analysis approaches. The analysis in the VLL focus on the investigations of the following criteria to achieve the intended visual effect, performance, and comfort 1. ADEQUATE QUANTITY OF LIGHT 2. SUITABLE SPATIAL DISTRIBUTION OF LIGHT 3. SUFFICIENT DIRECTIONALITY OF LIGHT 4. ABSENCE OF GLARE; AND 5. SUFFICIENT SPECTRAL CONTENT OF LIGHT The analyses in this paper have been limited to the study of the distribution and directionality of light. They are not exhaustive in nature; rather, they highlight some of the per-pixel analysis capabilities. 2 THE DESIGN SCENARIO The analysis capabilities are demonstrated utilizing the HDR images of an office located in Ann Arbor, Michigan. The images are generated with the Radiance Lighting Simulation and Rendering System (LBNL 2000, Ward and Shakespeare 1997). The room dimensions are 3.7m by 3.7m (12 ft. by 12 ft.); it has an inclined ceiling (15°) with an average height of 3.4m (11 ft.). It is located on the fourth floor of an office building. The wall, floor, and ceiling materials have 57 percent, 1 The University of Washington, Department of Architecture, Box 355720, Seattle, WA, 98195; 2 The University of Michigan, College of Architecture and Urban Planning, 2000 Bonisteel Boulevard, Ann Arbor, MI, 48108. inanici@u.washington.edu; moji@umich.edu LEUKOS VOL 3 NO 2 OCTOBER 2006 PAGES 89–104 © 2006 The Illuminating Engineering Society of North America doi: 10.1582/LEUKOS.2006.03.02.001 89