alembic: crash on import #75252
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Reference: blender/blender#75252
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Operating system: windows
Graphics card: n/a
Blender Version
Broken: latest master
Worked:
Short description of error
Reported on chat by @john-l (unsure if he has a phab user) but he was insecure about his English so i am unsure where this file came from or what created it . I have the following explanation to go with it
@john-l 11:39 Yes. If import abc file only has three points in first frame, and three point's position is same , then blender will crash.
which means nothing to me, but hey a crash is a crash and we ought to look at that :)
Exact steps for others to reproduce the error
Import the following alembic file:
debug.abc
Added subscriber: @LazyDodo
Changed status from 'Needs Triage' to: 'Confirmed'
The crash is caused by the Alembic file containing invalid edges, namely between the same vertex (so for example from vertex #0 to vertex #0). Blender doesn't support this; see the assert
BLI_assert(v0 != v1);
in edgehash.c. Mesh validation reports:Skipping arbitrary vertices or edges is not so easy with the current implementation of the Alembic importer, as it first allocates memory for the mesh elements and then iterates over the Alembic file to read the data to the allocated memory. In order to skip arbitrary mesh elements, we would have to reallocate the memory and copy the data, and then also add extra bookkeeping to ensure that other mesh data is still correct (edge indices in custom data layers, for example).
It is possible to call
BKE_mesh_validate()
after the mesh is loaded, to ensure that it is valid for further processing. However, on a quick test on my computer showed a performance drop from 17 FPS to 8 FPS (with my test export of the animated dog in Daily Dweebs).I see this as a limitation of Blender's current architecture, rather than a bug.
Changed status from 'Confirmed' to: 'Archived'
This was fixed in
973ab436f0
.