Volumetric breaks at mesh intersection

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phoenixart
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Volumetric breaks at mesh intersection

Post by phoenixart » Tue Sep 01, 2020 1:33 am

This is my first test with LuxCore Volumetrics, sorry if the solution has already been mentioned in the forum. I searched but no luck.
(Ignore the quality of the image, it's for testing purpose only)

Basically, I'm translating what I usually do in Cycles to Lux and I'm noticing something strange happening at the boundary of the ground plane.
lux-core-test-004-54sec.jpg
This is the same scene roughly translated for Cycles
luxVScycles-test-volumetric-40sec-002.jpg
As you can see, the background in Cycles gets more muted and the ground blurs into the environment in a more, gradual way.
In LuxCore there's a sharp separation between the ground plane and the volumetric.

On top of that, the light has sharp edges (having the light visible doesn't fix the problem).

Here's my basic setup for the volumetric cube:
Snipaste_2020-08-31_18-31-10.jpg
Any hints?
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FarbigeWelt
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Re: Volumetric breaks at mesh intersection

Post by FarbigeWelt » Tue Sep 01, 2020 6:59 am

phoenixart wrote:
Tue Sep 01, 2020 1:33 am
This is my first test with LuxCore Volumetrics, sorry if the solution has already been mentioned in the forum. I searched but no luck.
(Ignore the quality of the image, it's for testing purpose only)

Any hints?
I usually define an external volume called Air.Clear.Volume.Prio.0 first. Then I define further volume, the internal volumes. In your case Air.Homo.Vol.Prio.10.

IOR are predefined in an utility node.

Then I set World volume and define Camera volume by choosing Air.Clear....

The camera should be located outside your cube with Material Null.

I hope this helps as a useful hint.
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Dade
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Re: Volumetric breaks at mesh intersection

Post by Dade » Tue Sep 01, 2020 11:10 am

phoenixart wrote:
Tue Sep 01, 2020 1:33 am
Any hints?
Your scene is likely to have a wrong setup: have you assigned a volume to the camera ? In alternative you can assign world volume.
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Re: Volumetric breaks at mesh intersection

Post by phoenixart » Thu Sep 03, 2020 4:22 am

It turns out everything works fine if the camera is positioned outside the volume as FarbigeWelt suggested.

Thanks!
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FarbigeWelt
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Re: Volumetric breaks at mesh intersection

Post by FarbigeWelt » Thu Sep 03, 2020 8:00 am

phoenixart wrote:
Thu Sep 03, 2020 4:22 am
It turns out everything works fine if the camera is positioned outside the volume as FarbigeWelt suggested.

Thanks!
Thank you for your feedback. :)
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Re: Volumetric breaks at mesh intersection

Post by Dade » Thu Sep 03, 2020 10:44 am

phoenixart wrote:
Thu Sep 03, 2020 4:22 am
It turns out everything works fine if the camera is positioned outside the volume as FarbigeWelt suggested.
It works also if it inside and you assign the volume to the camera.
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Re: Volumetric breaks at mesh intersection

Post by phoenixart » Thu Sep 03, 2020 5:20 pm

Dade wrote:
Thu Sep 03, 2020 10:44 am
It works also if it inside and you assign the volume to the camera.

Thanks for the heads up, Dade.

How do I do that?
Is it related to this?
Snipaste_2020-09-03_10-19-34.png
Snipaste_2020-09-03_10-19-34.png (8.43 KiB) Viewed 183 times
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Re: Volumetric breaks at mesh intersection

Post by B.Y.O.B. » Thu Sep 03, 2020 5:38 pm

Yes. Disable auto-detection, and you will be able to specify the volume manually.
Auto-detection only works if the surface in the middle of the film has correct interior/exterior volumes assigned (e.g. in your case, fog as exterior volume). However since it can be annoying to go through all materials and specify the correct volumes, you can instead specify the camera volume manually.

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Re: Volumetric breaks at mesh intersection

Post by phoenixart » Thu Sep 03, 2020 6:49 pm

B.Y.O.B. wrote:
Thu Sep 03, 2020 5:38 pm
Yes. Disable auto-detection, and you will be able to specify the volume manually.
Auto-detection only works if the surface in the middle of the film has correct interior/exterior volumes assigned (e.g. in your case, fog as exterior volume). However since it can be annoying to go through all materials and specify the correct volumes, you can instead specify the camera volume manually.
Thanks, B.Y.O.B.

I disabled the Auto-Detect, created a new Camera Volume which has these settings by default
Snipaste_2020-09-03_11-45-43.png
And now I guess I can simply have my cube with the Homogeneous Volume extending past the camera.
Snipaste_2020-09-03_11-48-42.png
Do I need to change any setting in the Camera Volume shader?
At the moment the result hasn't changed, I'm back to the clipping issue in the first image I posted.
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Re: Volumetric breaks at mesh intersection

Post by B.Y.O.B. » Thu Sep 03, 2020 6:56 pm

If the camera is inside the fog, you need to set the fog volume as camera volume.
(it is the camera exterior volume)

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