[Bldg-sim] "Dynamic Radiance" and Radiance Terminology

Lars O. Grobe grobe at gmx.net
Mon May 17 19:08:21 PDT 2010

Hi Rob!
> Radiance has a marvelous evolutionary history spanning two plus decades; tools, materials and geometry primitives have all been added to Radiance over the years to add functionality to the suite. Yes, some real game changing tools have recently been added to Radiance, but it's still Radiance. Let's call the tool what it really is (Radiance v4.x), and agree to another term(s) for the process. Currently, this process is known as the three-phase approach, but I'm sure we can come up with a more interesting/fun one, or five or six that we can all argue over.
Well, sorry for all the cross-postings. I fully agree with your 
argumentation. We should keep things clear. Radiance has been a tool to 
simulate radiative energy transfer, and that is probably why it is 
called Radiance. This has not changed.

Radiance has always been used with scripts, to achieve very different 
goals. Thas has not changed neither, so Radiance always supported 
dynamic simulations, whatever that means.

People have been using Radiance with different sky models, and support 
for these has evolved. First, everyone was using gensky. This tool 
allows to generate a sky model only from choosing one of the old 5 CIE 
skies, location and time. Then, others included weather data on its 
lowest level by providing measured irradiance or radiance to gensky, 
which is able to consider these. Others developed other tools to include 
different sky models. And finally, what has become very popular these 
days, people use patch-based models of skies to simplify e.g. 
time-series over a full day, month or even year. Especially support for 
these has been improved in recent versions, over the last years.

So - Radiance is in version 4 now, and with every release new tools or 
features were included to improve support for the applications that 
seamed to be most interesting for the community. This does not match the 
naming schemes of commercial software, where companies love to simply 
rename an application from time to time to attract some interest or 
because someone thinks that one of the recent developments is so great 
to stamp a new label on it. For Radiance, I doubt this to be helpful. It 
is a generic simulation tool for a domain that has not changed since the 
first release. And clearness and transparency are a must in its 
application and support. So I would encourage people to be specific when 
naming it - give the version, and spell the application. What is wrong 
about doing weather-data based light simulation and reference Radiance 
4.1.4 later as the tool used?

Best regards,

Lars O. Grobe.

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