Last Thursday, I hit the airwaves, yakking about lighting simulation. For some reason the Boulder Green Building Guild was interested in my take on the use of simulation in optimizing the energy efficiency of building designs in the US, on the latest installment of Footprint Radio.

It was a thrill to share the half-hour with Kostas Papamichael from the California Lighting Technology Center, and my buddy Mike Plann from Lightlouver. I hope one or two people listen, and are intrigued enough to explore daylighting design, or at least turn off the lights once in a while.

The cool thing is I’m now in the iTunes Music Store. Check it out by listening to the show on the BGBG’s website, or by checking out the podcast on the iTunes Music Store.

Thanks again, Tasha, for having me on the show.

Once again, I have had a humbling experience working with Radiance. Just when you think you know even a little bit about this program, you are told otherwise, simply by attempting to learn more about it.

Details here: initial results with rtrace’s multiprocessing feature

9QM93TAVDT59

3421 seconds. That’s how long it took my new laptop to render the de facto radiance benchmark scene. That’s good enough for 13th place on the list, not bad for a laptop marketed to college kiddies and soccer moms. My old laptop is 36% slower in this test, and cost me $700 more than my new one. Amazing.

Full stats:
rpict user time: 3421
proc: Intel Core 2 Duo
cores: 1/2
clock speed: 2.4 GHz
cache: 3 MB
OS: OS X 10.5.6
Radiance ver: 4.0a
compiler: gcc 4.0.1
compile options: -O2 -ffast-math -funroll-loops
results: 691120680 rays
date: 2008-12-29
submitter: robg

I think that when you appear in the release notes for this software, you are officially a geek.

Scroll down a ways, through all kinds of compu-lighting-geekery, and you will discover that yours truly has added a tiny piece of functionality to a fantastically complex piece of software, software that excels at modeling the ultimate complexity, light.

While I realize that in comparison to all the work done by Greg Ward and several other giants in the Radiance community, my contribution—comprised of nothing more than a little copying and pasting from a shell script, I might add—amounts to the equivalent of a key grip credit on a Hollywood feature, I’m still pretty happy to see my name there, and I appreciate the credit.

Radiance User: “Boy, that objview script sure is handy for looking at scene geometry; if only there was something like that for looking at the distribution of my light source files.”

Announcer: “Well, THE WAIT IS OVER!! That’s right, now there’s a script that has the ease of use of objview, but is scientifically engineered for use with Radiance light source input files! Plus, if you call now, we’ll include K-Tel’s “70’s platinum hits”—on eight-track—absolutely free! Don’t delay, limited offer, operators are standing by, yadda-yadda-yadda.”

Ahem, sorry. In all seriousness, I took Greg Ward’s objview script and modified it to take a single Radiance scene input file and place it at 0,0,0, then surround it on five sides (top, bottom, E, N, W) with opaque surfaces. It sets -ab 1 and -ds .15 and then loads rview with a view looking into the box. The box is 48 units square by default; you can change the size of the box with the -bs switch. All the other options in objview are available in ltview.

ltview is useful for making sure the distribution of your light source is what you think it is, and that nothing went awry during the ies2rad conversion. It’s also good for checking replmarks triangle orientations.

Download your own copy of ltview here.

Hi. Miss me? So, for the last week or so I have been struggling to understand some screwy results I’ve been getting with Radiance, using the trans material to emulate some sun control shades. After a flurry of emails today from the very talented membership of the radiance-online.org mailing list, I think I have been shown the light. Specifically, I wanted to post a link to this very useful flowchart that illustrates the way all the trans parameters are interrelated (scroll down a bit for the image). Thanks, Schorsch.

The first rtrace computes the intersection point (which is fast) and the second rtrace does the illuminance
calculation. Cool, yes? Yes.