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Maniphest T86669

Motion Blur stop to work at a certain frame (animation) from alembic file.
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Description

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce RTX 2070 SUPER/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 461.92

Blender Version
Broken: version: 2.92.0, branch: master, commit date: 2021-02-24 16:25, hash: rB02948a2cab44
Worked: (newest version of Blender that worked as expected)

Short description of error
Importing an alembic file from Houdini to Blender, to instance spheres on lot of vertex points.
The problem occurs when I try to render the 467 frame to the 500th. Every frames before the 467th are working.
The problem disappears when I desactivate the motion blur. The motion blur works fine before the 467th frame, and for no reason stop working with huge huge render time.

Exact steps for others to reproduce the error
Import alembic file (from particles sim) to blender.
Instance spheres on.
Activate motion blur.
Render animation.

Event Timeline

emoctral renamed this task from Motion Blur bugged at a certain frame from alembic file. to Motion Blur stop to work at a certain frame (animation) from alembic file..Mar 17 2021, 6:15 PM
emoctral created this task.
emoctral removed a subscriber: emoctral.Mar 17 2021, 7:56 PM
emoctral added a subscriber: emoctral.
Romain Toumi (ToumiX) closed this task as Resolved.EditedMar 17 2021, 8:25 PM
Romain Toumi (ToumiX) claimed this task.
Romain Toumi (ToumiX) added a subscriber: Romain Toumi (ToumiX).

Cycles creates motion blur on the instantiated objects that are following cloud points.

the disappearing points are causing the index of the points to change, which causes the spheres to follow point, thus creating a huge motion blur.
that explains the very long rendering time and the "globally blurry" image

you have to disable the "reap particles" option on houdini and it works

Blender is not involved in this issue