Mesh imported from alembic crashes later
Closed, ArchivedPublic

Description

System Information
Running: Windows 10 x64 with a gtx 1080 and plenty of ram.

Blender Version
2.78a

Alembic mesh created from "Quill" for Oculus frequently crashes in Blender. I'm not sure if Quill is creating bad geometry, or if Blender is behaving poorly, but I suspect Blender is at fault.
degenerate_crash.blend - has .abc file imported and relevant mesh isolated.
degenerate_crash.abc - source .abc file

Exact steps for others to reproduce the error
Here is some of the bad behavior I'm seeing:
-> Open the blend file.
-> Run the "separate" op.
-> Choose "Loose Parts"
-> Crashes with Error: EXCEPTION_ACCESS_VIOLATION
Not all mesh from Quill exhibit this crash, but the one attached does.

-> Open the blend file.
-> Run "degenerate dissolve" op.
-> Crashes with Error: EXCEPTION_ACCESS_VIOLATION
All Quill meshes that I've tested crash Blender doing this.

I think the issue lies with Blender. Maya doesn't seem to have any issue with this abc. If I exporting the mesh again from Maya -> Blender, Blender no longer crashes. It is possible that Maya fixes a problem with the mesh, or there is something unexpected in the way Quill is creating the Alembic file.

While the mesh does appear to have degenerate geometry (uv unwrapping it creates some very odd results), I'm not sure if this is a result of the import process or if it's in the actual abc file.

Details

Type
Bug
Bastien Montagne (mont29) triaged this task as "Normal" priority.

@Kévin Dietrich (kevindietrich) think you should call BKE_mesh_validate from importer (as we usually do in py add-ons importers), to ensure we have valid mesh data in the end?

@Bastien Montagne (mont29), since Alembic can store hundreds of objects and since BKE_mesh_validate can slow down the import process, it is not called directly, but there is an option in the import settings for it.

@Jordan Hueckstaedt (assumptionsoup), could you try importing the file with the "Validate Meshes" option checked?

Oh awesome! That check box seems to fix the problem. My models are small enough I don't even notice a slow down checking it. UV unwrapping the model no longer produces bizarre results, and separate/dissolve degenerates no longer crash Blender!

Thanks guys!

I guess we can close this since the issue appears to be resolved.

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