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Maniphest T83996

Boolean modifier interferes with rigid body physics
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Description

System Information
Operating system: Darwin-20.2.0-x86_64-i386-64bit 64 Bits
Graphics card: AMD Radeon Pro 5500M OpenGL Engine ATI Technologies Inc. 4.1 ATI-4.2.13

Blender Version
Broken: version: 2.92.0 Alpha, branch: master, commit date: 2020-12-17 20:43, hash: rB23233fcf056e
Worked: unknown

Short description of error
When a rigid body has an active boolean modifier, its physics are messed up and the object stays in its original location for most of the time, showing in the correct location only in a few random frames. This depends on the collision shape: convex hull and mesh work as expected, the others show the above problem; and only after the results are cached or baked, not on the first run.

Exact steps for others to reproduce the error
See attached blend file.

Bool physics bug.blend1 MBDownload

Results with boolean modifier and sphere collision shape:

After either removing the modifier, or changing the shape to convex hull or mesh:

Event Timeline

Wouter Stomp (wouterstomp) created this task.Dec 20 2020, 9:56 PM
Wouter Stomp (wouterstomp) added a comment.Dec 20 2020, 10:07 PM

With convex hull and mesh collision shapes it also happens, but then only when there is actually an object selected in the boolean modifier; it also happens on the first run in that case.

Wouter Stomp (wouterstomp) renamed this task from Boolean modifier interferes with rigid body physics depending on collision shape to Boolean modifier interferes with rigid body physics.Dec 20 2020, 10:10 PM
Robert Guetzkow (rjg) added a subscriber: Robert Guetzkow (rjg).EditedDec 21 2020, 2:01 PM

I don't think that this is a supported use case. What would even be the intended result if a rigid body performs a boolean operation on collision?

Robert Guetzkow (rjg) changed the task status from Needs Triage to Needs Information from Developers.Dec 21 2020, 2:03 PM
Robert Guetzkow (rjg) added projects: Modeling, Nodes & Physics.
Richard Antalik (ISS) closed this task as Archived.Dec 27 2020, 8:01 PM
Richard Antalik (ISS) added a subscriber: Richard Antalik (ISS).

This setup creates dependency cycle between boolean modifier and rigidbody simulation. This is not supported indeed.

You can see this dependency cycle reported in Window > Toggle System Console.