Metaball particles are handled inconsistently in Geometry Nodes #100639

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opened 2022-08-26 11:01:29 +02:00 by Sun Kim · 8 comments
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System Information
Operating system: Windows-10-10.0.19043-SP0 64 Bits
Graphics card: Radeon RX 570 Series ATI Technologies Inc. 4.5.0 Core Profile Context 22.7.1.220725

Blender Version
Broken: version: 3.4.0 Alpha, branch: master, commit date: 2022-08-25 09:50, hash: d4764a385a
Worked: (n/a)

Short description of error
Metaball rendered via particles are handled inconsistently in Geometry Nodes. It seems only mesh related nodes are generally working well with them.

I wasn't sure about reporting this as a bug, because I assume that compatibility with the particle system is probably not intended use case. I guess ability to access metaball particles at all is an unintended bonus from eaa87101cd5a? I'd argue that if this can be easily "fixed" it will open up some interesting use cases before actual simulation/physics nodes arrive, but this is a borderline feature request and I guess developers will decide if this is worth to look at at this point.

Exact steps for others to reproduce the error

MetaballParticles.blend
MetaballParticles.mp4

**System Information** Operating system: Windows-10-10.0.19043-SP0 64 Bits Graphics card: Radeon RX 570 Series ATI Technologies Inc. 4.5.0 Core Profile Context 22.7.1.220725 **Blender Version** Broken: version: 3.4.0 Alpha, branch: master, commit date: 2022-08-25 09:50, hash: `d4764a385a` Worked: (n/a) **Short description of error** Metaball rendered via particles are handled inconsistently in Geometry Nodes. It seems only mesh related nodes are generally working well with them. I wasn't sure about reporting this as a bug, because I assume that compatibility with the particle system is probably not intended use case. I guess ability to access metaball particles at all is an unintended bonus from eaa87101cd5a? I'd argue that if this can be easily "fixed" it will open up some interesting use cases before actual simulation/physics nodes arrive, but this is a borderline feature request and I guess developers will decide if this is worth to look at at this point. **Exact steps for others to reproduce the error** [MetaballParticles.blend](https://archive.blender.org/developer/F13418252/MetaballParticles.blend) [MetaballParticles.mp4](https://archive.blender.org/developer/F13418242/MetaballParticles.mp4)
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Added subscriber: @persun

Added subscriber: @persun
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Added subscriber: @PratikPB2123

Added subscriber: @PratikPB2123
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Changed status from 'Needs Triage' to: 'Needs Developer To Reproduce'

Changed status from 'Needs Triage' to: 'Needs Developer To Reproduce'
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Added subscriber: @HooglyBoogly

Added subscriber: @HooglyBoogly
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Thanks for the report. I'm able to repro it.
Not sure if this would be considered as a bug because meta-balls were not supported until eaa87101cd
We also have similar report: #87230 (Point Instance node doesn't instance meta objects.) (maybe we can now close this after the above commit)
@HooglyBoogly , can you look at this?

Thanks for the report. I'm able to repro it. Not sure if this would be considered as a bug because meta-balls were not supported until eaa87101cd We also have similar report: #87230 (Point Instance node doesn't instance meta objects.) (maybe we can now close this after the above commit) @HooglyBoogly , can you look at this?
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Actually the issue seems to be putting the particle system and GeoNodes in the same object. If you put the particle system and GeoNodes to different objects it works fine.

MetaballParticlesGNTest.mp4

MetaballParticlesGN.blend

Actually the issue seems to be putting the particle system and GeoNodes in the same object. If you put the particle system and GeoNodes to different objects it works fine. [MetaballParticlesGNTest.mp4](https://archive.blender.org/developer/F13427059/MetaballParticlesGNTest.mp4) [MetaballParticlesGN.blend](https://archive.blender.org/developer/F13427054/MetaballParticlesGN.blend)
Member

Thanks for the report. I think this comes down to incompatibilities with the particle system like you mentioned in the report. There are two different systems for instancing in play, and the "multi-geometry-type output" from geometry nodes doesn't play well with the particle system, similar to the cause of #93159.

I'll leave this as a known issue since there's no harm in documenting it. Eventually when removing the particle system these issues will be closed anyway.

Thanks for the report. I think this comes down to incompatibilities with the particle system like you mentioned in the report. There are two different systems for instancing in play, and the "multi-geometry-type output" from geometry nodes doesn't play well with the particle system, similar to the cause of #93159. I'll leave this as a known issue since there's no harm in documenting it. Eventually when removing the particle system these issues will be closed anyway.
Member

Changed status from 'Needs Developer To Reproduce' to: 'Confirmed'

Changed status from 'Needs Developer To Reproduce' to: 'Confirmed'
Philipp Oeser removed the
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Reference: blender/blender#100639
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