Faster Radiance on Windows

radiance-general
1

Latest release include has some important updates for Windows users:

  1. Experimental multi-processing rcontrib: now rcontrib can be run with -n > 1. It’s a workaround for the lack of fork() on Windows. Do expect larger memory footprint. Stability on real world models untested.
  2. In general much better Windows ray tracing performance, should be on par with MacOS and Linux.
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2

Great news! I will be testing it over the next few days. Thanks!!

3

This is super exciting @Taoning_Wang1! I’m trying to run rfluxmtx with n > 1 on Windows now, but it doesn’t seem to be working.

vwrays -vtv -vp -7.968 2.611 7.978 -vd 1 0 0 -vu 0 0 1 -vv 90 -vh 120 -x 600 -y 300 -pj 0.7 -c 9 -ff | rfluxmtx -n 8 -v -ffc -x 520 -y 300 -o glazing_1/g1%03d.hdr -ab 2 -ad 200 -lw 1e-2 -c 9 - glazing_1.rad -i scene.oct
rfluxmtx: running: rcontrib -fo+ -n 8 -o glazing_1/g1%03d.hdr -ab 2 -ad 200 -lw 1e-2 -x 520 -y 300 -ffc -c 9 -f klems_full.cal -p RHS=+1 -bn Nkbins -b kbin(1.22465e-16,1,-9.05942e-14,0,0,1) -m m000005 "!oconv -f -i scene.oct glazing_1.rad"

Only one thread is utilized. My Radiance version is RADIANCE 6.1a 2026-01-30 LBNL (6.1.74b430c613).

4

Sorry about that. Looks like I forgot to update one of the header files.

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5

I checked in the missing files from @Taoning_Wang and the latest HEAD containing the necessary changes is compiled here.

Best,
-Greg

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6

Hi @Taoning_Wang1,

There seems to be an issue when reading some sensor files when using n > 1 on Windows. Here is the rfluxmtx call and the error.

rfluxmtx -I -ab 2 -ad 512 -c 1 -faf -n 16 -y 221 - sky.dome -i scene.oct < grid.pts > results.dc
rcontrib: system - PeekNamedPipe() failed: No such file or directory

Do you know what the issue is? Let me know if you have any questions. If I set -n to 1 or just remove -n completely it runs without issues.

I am using the latest version: RADIANCE 6.1a 2026-02-22 LBNL (6.1.a69eae17fd).

Here is a downloadable sample. There is another sensor file in the ZIP, 884.pts, which is not causing any issues: Google Drive

7

Thanks, Mikkel. This is really helpful. The difference between your working input file and the non working input file is whether the input contains value “6.5”. It’s a weird Windows bug. I am working on a fix now.

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8

@Taoning_Wang1 just checked in a new build that should hopefully fix this issue. It is included in the lastest Radiance HEAD release.

-G

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