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Maniphest T86522

Blender hair to unreal alembic crash caused by length vertex group
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Description

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce RTX 2080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 461.72

Blender Version
Broken: version: 2.91.2, branch: master, commit date: 2021-01-19 16:15, hash: rB5be9ef417703
Worked: (newest version of Blender that worked as expected)

Short description of error
Hair particles with length driven by vertex group exported to Unreal via abc causes Unreal to crash after fiddling a bit around with hair inside UE (using RHI DX12, Error: GPU Crashed or D3D Device Removed). Crash is inevitable, and will happen in any case, all the time.
If length of hair particles inside Blender is no more driven by vertex group, and such exported the same way to Unreal, no more crash.

alembic_bug.blend3 MBDownload

Exact steps for others to reproduce the error

Crash version:

  • open attached blendfile, and select scalp mesh
  • Export the scalp mesh as FBX
  • Export hair particles as ABC (Settings different than default: Scale(100), Selected Objects(checked), Renderable Objects (unchecked), Visible Objects (checked), the rest is default.)
  • import ABC hair (Import Options: Rotation X90, Y0, Z0, Scale X1, Y-1, Z1)
  • Import scalp mesh into unreal, put into scene, create blueprint on scalp mesh with groom component, Assign imported groom asset inside groom component.
  • fiddle around (open hair, play with parameters, or just select scalp mesh, and click on groom component in details pane, or just do whatever you want.. ) sooner or a bit short later, crash will come.

No-crash version:

  • open attached blendfile, and select scalp mesh
  • go to particle properties, and under vertex groups remove assigned length vertex group
  • repeat export/import steps from Crash version.
  • no crash inside unreal

Event Timeline

Marek Hollý (asil8567) created this task.Mar 12 2021, 10:57 AM
Marek Hollý (asil8567) updated the task description. (Show Details)Mar 12 2021, 11:01 AM
Philipp Oeser (lichtwerk) changed the task status from Needs Triage to Needs Information from User.Mar 12 2021, 2:17 PM
Philipp Oeser (lichtwerk) added a subscriber: Philipp Oeser (lichtwerk).

Since the roundtrip back into blender seems to have no problems and I dont have access to Unreal, we would at least have to know why this crashes in Unreal.
(also could not spot any issue with the binaries like abcecho)

Has this been reported to Unreal?
Please do so (and report back what they said), you can always reference this task here and they could reach out if there are problems on the blender side.
Until then, I would assume this is a problem on the Unreal side.

Marek Hollý (asil8567) added a comment.Mar 12 2021, 3:03 PM

Ok, Submitted to Epic. I will come back with their reply.
Marek

Marek Hollý (asil8567) added a comment.Mar 16 2021, 8:08 AM

Ok, here is reply from Epic. So no issue on Blender or Epic side. but on Nvidia..

Hello,

This is an issue we are waiting for Nvidia to address. You can track the bug on our end here: https://issues.unrealengine.com/issue/UE-92814.

There is no exact workaround for this issue. Some people see the problem; others do not. A workaround may work for one person but not another. It is very dependent on the hardware and drivers, which differ from person to person. There are a lot of forum entries out there where people talk about how they get around the issue. I suggest checking those out for things to try.

Thanks,

Elijah

Philipp Oeser (lichtwerk) closed this task as Archived.Mar 16 2021, 9:35 AM

OK, thx getting back @Marek Hollý (asil8567) .

Since there is nothing we can really do on our side, I will archive this for now.
If Epic gets new information it would still be appreciated if this information gets forwarded here, we can also reopen in case there is still something wrong after Epic marks this as resolved.