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Dependency Cycle Detected when copying objects with cloth and collision modifier
Open, Needs Information from UserPublic

Description

System Information
Operating system: Windows 10
Graphics card: Geforce GTX 1080 Ti

Blender Version
Broken: 2.80

Short Description
If you copy objects that have a collision and cloth modifier attached to them (or copy the modifiers to another object), a dependency cycle is detected. This is really frustrating once you work with 10+ objects because blender re-detects the circular dependencies on every redo/undo and project load, making you wait for a good 30 seconds to a minute depending on the complexity of the scene.

Exact steps for others to reproduce the error

  1. attach collision and cloth modifier to cube in startup project.
  2. Copy the cube.
  3. check console output.

The output should be something like this:

Dependency cycle detected:
  OBCube.001/Geometry Component/GEOMETRY_EVAL() depends on
  OBCube/Geometry Component/GEOMETRY_EVAL() via 'Cloth Collision'
  OBCube.001/Geometry Component/GEOMETRY_EVAL() via 'Cloth Collision'
Dependency cycle detected:
  OBCube.001/PointCache Component/POINT_CACHE_RESET() depends on
  OBCube/Geometry Component/GEOMETRY_EVAL() via 'Point Cache'
  OBCube.001/Geometry Component/GEOMETRY_EVAL() via 'Cloth Collision'
  OBCube.001/PointCache Component/POINT_CACHE_RESET() via 'Point Cache -> Geometry'
Detected 2 dependency cycles

Alternatively you can simply open the attached blend file and check the console output. For a simple test like this, it wont noticeably slow down the project but once you copy an object a couple of times the dependency circles appear to exponentially grow and slowing things down to a halt.

Details

Type
Bug

Event Timeline

Jacques Lucke (JacquesLucke) triaged this task as Needs Information from User priority.

Did this work in older versions of Blender? I'm not entirely sure which kinds of interactions the current cloth system supports.

Did this work in older versions of Blender? I'm not entirely sure which kinds of interactions the current cloth system supports.

I am a new user to blender, so I would not know. I'll try to test it.

For complex scenes with a lot of identical cloth objects this bug really bites you in the butt because you can neither copy the objects directly nor copy the physics modifiers from one object to another without running into this issue. It will essentially make the whole blender file unusable because the dependency cycles will exponentially grow and it will re-detect them on every action, undo, redo, project load.