Optical simulation - Reflection of sun beams

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andy1988
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Joined: Mon Nov 05, 2018 7:42 pm

Optical simulation - Reflection of sun beams

Post by andy1988 » Tue Nov 06, 2018 3:46 am

Bidir+Sobol
Blender 2.79b
BlendLuxCore 2.1alpha3 (compiled from git tag with that version).

Playing with mirrors and beams. Would prefer to see beams in homogeneous volume with sky+sun active as I'm interested in varying the sun angle. Disabled sky+sun to see the beams better, and emit light beam directly from mirrors as a workaround.

Noticed odd thing. Light scattering only scatters after the beam is reflected (or if beam portion never reflected it scatters just fine). Changing eye depth & light depth does not change this. This effect is fine with me, and to be honest, preferable, but I thought I'd share.

See 1:
WhtAdsorption2.5m_SS0.01_LYllwScatter_17000Lm_nodish.jpg
Then see 2, with reflecting dish:
WhtAdsorption1.0m_SS0.01_LYllwScatter_17000Lm_dish.jpg
And 3 better shows reflection twice. It is redder on second beam bounce:
WhtAdsorption0.2m_SS0.01_LYllwScatter_17000Lm_dish_redreflect.jpg
Any suggestions on getting beams visible in sky+sun appreciated, thank you. Right now beams are barely perceptible:
BluAdsorption2.5m_SSS0.10_LYllwScatter_blkemission.jpg
To get the beams visible with sky+sun I'm thinking of using:
  • A shadow over beams & scattering volume, but not occluding mirror
  • Adjusting gains?
  • Some sort of optical filtering trick? Polarizing filter? Changing reflection color doesn't seem to work by itself
  • Light baffling. Mirrors reflect light into dark chamber, which has homogeneous scattering volume. This is what I'd expect to do with real light to make beams visible! But maybe there are other tricks? Now that I think about it, I really ought to just do this instead of asking.
My interest includes things like Light tubes for distributing sunlight. I've seen some light tubes featured in a data center, pretty neat. They used them underground to minimize heat produced and minimize energy expense. It was very beautiful lighting in rooms carved into rock. Unfortunately I haven't been able to find the article about it again.
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Dade
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Re: Optical simulation - Reflection of sun beams

Post by Dade » Tue Nov 06, 2018 8:39 am

andy1988 wrote:
Tue Nov 06, 2018 3:46 am
Noticed odd thing. Light scattering only scatters after the beam is reflected (or if beam portion never reflected it scatters just fine).
This is likely to happen because the default world volume is not set: you need to set the volume used for rays starting from camera otherwise no volume will be applied for the first segment of the eye path.
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B.Y.O.B.
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Re: Optical simulation - Reflection of sun beams

Post by B.Y.O.B. » Tue Nov 06, 2018 9:59 am

There was a bug in the camera's automatic volume detection that has been fixed recently.
You should compile the latest sources or download v2.1beta1.
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andy1988
Posts: 2
Joined: Mon Nov 05, 2018 7:42 pm

Re: Optical simulation - Reflection of sun beams

Post by andy1988 » Wed Nov 07, 2018 6:23 am

Dade wrote:
Tue Nov 06, 2018 8:39 am
This is likely to happen because the default world volume is not set: you need to set the volume used for rays starting from camera otherwise no volume will be applied for the first segment of the eye path.
Yes this works as expected with the default world volume, I didn't think to try that, thank you:
WhtAdsorption0.2m_SS0.01_LYllwScatter_17000Lm_dish_Volume.jpg
I'm very happy to have it working :) Neat stuff

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