Radiance software - physically based light simulation
Light simulations and rendering at pab-opto currently use mostly the
Radiance Synthetic Image System.
Radiance offers light simulation based on physical laws and generating quantitative results
radiance, irradiance, luminance, illuminance).
links and talks on my Radiance and BRDF/BSDF data, models and measurements
talk on first results measuring spectral BSDF, 2014, London
Introducing spectrally resolved BSDF and other updates on the PG2 gonio-photometer
July 2013, arXiv.org > physics > arXiv:1307.4214
Review of simulating four classes of window materials for daylighting with non-standard BSDF using the simulation program Radiance
invited lectures at the 10th Radiance workshop, 2011 Berkeley:
measuring & modelling BSDF step 1: Radiance plastic, metal, trans parameters based on material data
some thoughts on future of BSDF materials, models & Radiance
(including thoughts on error bounds and precision in simulation)
July 2011: started BSDF,BRDF database of some building materials at www.pab.eu/bme
invited extended lecture on principles, measuring and modelling of BRDFs / BSDF
at the 9th Radiance workshop, 2010 Freiburg.
pab-opto inaugurated and managed Radiance-Online from August 2000 to
July 2006. During the 6 years it evolved from an unofficial ''pirate''-state, inaugurated during a crisis of official Radiance
distribution, to the official software archive. Plus multiple mailing lists with approx. 300 users.
The server had been physically shipped to LBNL (Lawrence Berkeley Lab) in June 2007 and is managed by LBNL staff since then.
talk on gonio-photometer II updates in 2006
5th International Radiance Workshop, September 2006
PDF version pab-radworkshop2006.pdf
talk on material modelling at the
Third International Radiance Workshop, October 2004
PDF version pab-radworkshop2004.pdf
Animations of detector paths, shown in this talk:
original MPEG format from 2004:
converted to MP4 in 2019:
A newer and better MP4 path animation of the PG2 are found on the PG2 webpages
quantitative test of Radiance's photon-map extension (forward raytracing)
talk on material modelling at the
First International Radiance Workshop, September 2002
PDF version pab-radworkshop2002.pdf
introduction to the
BRDF and material modelling (2002)
PDF version pab_radiance_talk_2002.pdf
Radiance simulation of Kimbell Art Museum (2000)
talk about light simulation (in German)
case study: modelling (laser) range scanners
Additionally to what is offered by the standard Radiance package, we use a substantial amount of proprietary extensions and tools.
Some of these tools are publicly available.
- quantitative results (both images and singular values)
- validated by various studies
- considers most light paths: indirect illumination and optionally caustics (extra module)
- scales well with large scenes (millions of objects)
- code is public and open source, making it possible to verify algorithms directly
- extended rendering: depth-of-field, stereo images and animations
Alternatives to Radiance
Advantages of Radiance: Results checked over years, code considered stable, low memory footprint of core engine, supported by
author and (if funds are available) by institute LBNL, support by fellow users via email list. It has been used by commercial companies on
commercial scale projects over 2 decades. Since any add-on to the core has to pass through Greg Ward, the code has been very stable and
therefore reliable. And, probably the most important feature: It doesn't suffer from advertising hype and wild we-can-do-all PR statements.
Drawbacks: Anyone adding to the core code suffers from its non-modular structure. That and the tenacious lack of robust automated test scenes (as of
Sep 2014) limit the writers of source code for the core engine to a very small number (say maximum of 3 people over the last 25 years).
Therefore, the core rendering engine is trailing current technology development. In terms of computer-graphics it is in many ways not
cutting-edge. It is very difficult to get any feature into Radiance for which there is no interest by Greg Ward or funding at LBNL.
The user interface, a problem over many years, is getting better since Radiance was built into a broader framework, e.g.
OpenStudio by NREL.
Alternatives: There are some commercial simulation programs out, whose advertising claims to handle everything (especially in my
field of BSDF data import and models), but in fact they do not. Since there's no source code available to check, it would be pretty bad to
base consulting work on that.
In optical industry, some well established, reliable ray-tracing programs, e.g. Zemax, Optis and others, have BSDF import features, which
are more or less well documented. But getting the vital details requires NDAs, if they are available at all.
PBRT is probably the best alternative to look into. A modular, public domain (source
available) program, with an established user base. How much this can be used for quantitative analysis is an interesting topic of
Author's experience with Radiance has been accumulating since Radiance Revision 1.2 in March 1990.
First at Fraunhofer Institute for solar Energy, than at pab-opto.
web address of this page: http://pab-opto.de?d=/radiance
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