BME BSDF, BRDF data, introduction

summary

Light reflectance of surfaces or transmission through materials is described by a quantity known by a few different names: BSDF BRDF. BRTF, All these acronyms refer to the same quantity, and share the same mathematical definition.
The BME (building material examples) BRDF or BSDF web-pages are a small collection of high precision BRDF,BSDF data on light reflection/transmission of materials. It contains specifically materials commonly found in the architectural sector.

BRDF, BSDF data is measured with a pgII scanning gonio-photometer. This data is then fitted to BRDF,BSDF functions, a standard way of using metrial data in optical simulation programs. The examples start with the Ward BRDF plastic model, which is the most used material in the light simulation program Radiance.
The resulting parameters exemplify the usage of data to validate light simulation within the architectural planning process. Statements on quantitative error for different models of the BSDF are included, and comparisons between models is shown.
These web-pages are intended to address the novice user (please see "where to start"), as well as providing details to readers with existing background in BSDF. For the sake of simplicity the term BSDF is used.

Please feel free to contact pab Ltd, http://www.pab.eu/ in case of questions.

role of material data for reflection/transmission data in the building sector

• trustworthy material data to light simulation instead of guesses leads to
• reliable simulation of lighting, which is basis for
• estimation of glare, energy and comfort at planning stage, so it
• support design vision by an adapted choice of suitable materials for day-lighting and lighting in general

our aim

• We are interested in the amount of energy reflected from or transmitted by a material, modelled in lighting programs with the lowest possible error.
  The example data on these web-pages presents a lot of quantitative detail, rarely found elsewhere.
• It is published to serve as a starting point for the most frequently used material plastic in the Radiance light simulation program.
  Additionally, quantitative data is presented on the quality of this basic model: In which cases it models real materials with high precision, and in which cases it lacks precision. The latter then needs more elaborated methods of modelling.
• In comparison, a number of BSDF,BRDF sites exists, but most are focused on stunningly looking surfaces in Computer Graphics. This does not imply that the light reflection is close to real materials .
  In contrast, here, models and fitting are done with a focus on simulating quantitative light transport (reflection and transmission) of a material. Hence, there is no particular emphasis that a surface looks ''nice'' or ''realistic''. To get more visually appealing surfaces, details like textures, bump-maps etc could be added to the basic physical model, but that's not the main point here.

links

The BME BSDF database web-pages are a service of pab advanced technologies Ltd, thank you for your interest in our web-pages.
Disclaimer: Data is believed to be accurate, but is supplied without any warranty, what so ever. Check our license for details.