Blocky pyro after rendering

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merb
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Hello

I currently have an issue I've never had before. In certain areas my pyro sim is blocky. The blocks are way larger than my voxel size (0.02) and there are much smaller details in the sim so I don't think it's caused by the voxel size.
I can't see these artefacts in my viewport so I believe it has something to do with Mantra/the Pyro Shader.

I scatter points in a volume that feed a pyroburstsource which feeds a volumerasterizeattributes and then the pyro solver. The shader is used from one of the content library pyro examples.

Might be something very obvious but I feel like I tried every parameter in my source, sim, shader and mantra node...
Ideas are appreciated

Cheers
Max

EDIT: It's a sparse sim but the result is the same with sparse turned off.

My system:
Ryzen 9 5900X
3080ti
128GB RAM
Edited by merb - Nov. 25, 2021 14:04:27

Attachments:
blocky_pyro.png (318.9 KB)
blocky_pyro_viewport.png (78.6 KB)

18.5.696
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It is a bit hard to tell from the image.

You said you are using Mantra right?

What are your maximum volume values? Are you using scattering on the pyro bake volume? What is your Blur Downsample value?

Do you have a scene file to share?
merb
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Hi, thanks for your fast reply.

Yes I'm rendering with Mantra.

Volume Limit: 1 (tried 4 didn't change it)
Yes I'm using scattering and the issue probably comes from that. If I turn it off I get no flames but the volume is nice and smooth.
Blur Downsample: 2x (tried 8x didn't change it)

A scene file is attached.

Thank you so much for your help

Attachments:
blocky_pyro.hiplc (1.9 MB)

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There are couple of things i have noticed which possible all contribute in some degree:

  • your density values are super high. You source in density with ADD operation with x10 scale. On top you are also emit density from flame with a x35 scale. That's a lot! And on top you are multiplying that by x3 for the render.
  • I adjusted some of the settings, along with reducing the expansion, which i realised was making the simulation expand too much.
  • the rasterized source volume is rather blocky as well. I also made some adjustments there.
  • You have enabled Velocity Blur on the geo, but you also have to enable Allow Motion Blur on the Mantra node.

Let me know if it works for you. (I edited the file in 19.0.445 but later i realised you are on 18.5, but that should not really matter at the end)
Edited by ati - Nov. 25, 2021 18:32:43

Attachments:
blocky_pyro_fixed.hipnc (1.5 MB)
pyro_render.png (1.3 MB)

merb
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Thank you so much for taking the time to have a look at my hip file. Incredibly helpful feedback.
Worked in 18.5 as well
18.5.696
Win 10
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