cloth object connected to 2 rigid bodies does not animate correctly #77190

New Issue

Maduranga Jayamaha · 2020-05-30T05:35:50+02:00

2020-05-30 05:35:50 +02:00

System Information
Operating system: Windows-7-6.1.7601-SP1 64 Bits
Graphics card: GeForce GTX 1060 6GB/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 388.13

Blender Version
Broken: version: 2.82 (sub 7), branch: master, commit date: 2020-03-12 05:06, hash: 375c7dc4ca
Also Broken in version: 2.90.0 Alpha, branch: master, commit date: 2020-05-29 18:08, hash: 2ee94c954d
And in: 2.83 (sub 17), branch: master, commit date: 2020-05-29 09:59, hash: 1d2b89304a

Short description of error
Cloth Object pinned to 2 rigid bodies does not animate correctly

Exact steps for others to reproduce the error

Open the attached SingleballoonAnimationBugReport.blend file{F8587541}
Play the animation and notice that there is

an animated cube called "connector" which is a passive rigid body,
a sphere called "ball" which is an active rigid body
An empty object called 'Constraint' which has a rigid body constraint of type 'point' applied between the cube and the sphere
A cylindrical object called 'string' which has a hook modifier applied to it, to connect it's top most points to the sphere. The 'string' is parented to the cube.

Go to scene properties and notice that the gravity has a positive value in z direction, which is the reason for the ball to try to float away rather than fall down.
Select the string object -> go to physics properties and apply 'Cloth'. In the Cloth settings, under Collisions dropdown disable the Object Collisions checkbox.
Now when you play the animation the string object doesn't move. This is wrong because the string is now suppose to float away while being connected to the sphere from the top end. SingleballoonAnimationBugReport2ClothApplied.blend
In the Cloth settings go to Shape -> in the Pin Group datafield select 'pinned' vertex group.
Play the animation and notice that the 'String Object doesn't animate like a cloth. SingleballoonAnimationBugReport2ClothAppliedAndPinned.blend

If I remodel the 'String' object and repeat the steps the animation sometimes work correctly. But this is quiet annoying as I have come across this issue in other places where there is cloth simulation. My final intention is to create a bunch of these animations but it's very hard to do as it sometimes do not work as there seems to be an annoying issue with the cloth animation that only works sometimes and fail in other times.
Thanks!

**System Information** Operating system: Windows-7-6.1.7601-SP1 64 Bits Graphics card: GeForce GTX 1060 6GB/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 388.13 **Blender Version** Broken: version: 2.82 (sub 7), branch: master, commit date: 2020-03-12 05:06, hash: `375c7dc4ca` Also Broken in version: 2.90.0 Alpha, branch: master, commit date: 2020-05-29 18:08, hash: `2ee94c954d` And in: 2.83 (sub 17), branch: master, commit date: 2020-05-29 09:59, hash: `1d2b89304a` **Short description of error** Cloth Object pinned to 2 rigid bodies does not animate correctly **Exact steps for others to reproduce the error** 1. Open the attached SingleballoonAnimationBugReport.blend file{[F8587541](https://archive.blender.org/developer/F8587541/SingleballoonAnimationBugReport2.blend)} 2. Play the animation and notice that there is - an animated cube called "connector" which is a passive rigid body, - a sphere called "ball" which is an active rigid body - An empty object called 'Constraint' which has a rigid body constraint of type 'point' applied between the cube and the sphere - A cylindrical object called 'string' which has a hook modifier applied to it, to connect it's top most points to the sphere. The 'string' is parented to the cube. 3. Go to scene properties and notice that the gravity has a positive value in z direction, which is the reason for the ball to try to float away rather than fall down. 4. Select the string object -> go to physics properties and apply 'Cloth'. In the Cloth settings, under Collisions dropdown disable the Object Collisions checkbox. Now when you play the animation the string object doesn't move. This is wrong because the string is now suppose to float away while being connected to the sphere from the top end. [SingleballoonAnimationBugReport2ClothApplied.blend](https://archive.blender.org/developer/F8574743/SingleballoonAnimationBugReport2ClothApplied.blend) 5. In the Cloth settings go to Shape -> in the Pin Group datafield select 'pinned' vertex group. Play the animation and notice that the 'String Object doesn't animate like a cloth. [SingleballoonAnimationBugReport2ClothAppliedAndPinned.blend](https://archive.blender.org/developer/F8587563/SingleballoonAnimationBugReport2ClothAppliedAndPinned.blend) If I remodel the 'String' object and repeat the steps the animation sometimes work correctly. But this is quiet annoying as I have come across this issue in other places where there is cloth simulation. My final intention is to create a bunch of these animations but it's very hard to do as it sometimes do not work as there seems to be an annoying issue with the cloth animation that only works sometimes and fail in other times. Thanks!

Maduranga Jayamaha commented

2020-05-30 05:35:50 +02:00

Added subscriber: @maduranga

Richard Antalik commented

2020-06-02 01:00:40 +02:00

Added subscriber: @iss

Richard Antalik commented

2020-06-02 01:00:41 +02:00

Changed status from 'Needs Triage' to: 'Needs User Info'

Richard Antalik commented

2020-06-02 01:00:41 +02:00

@maduranga This is quite complex file and steps. Is it possible to reduce number of elements and steps to minimum?

Maduranga Jayamaha commented

2020-06-03 20:37:49 +02:00

Changed status from 'Needs User Info' to: 'Needs Triage'

Maduranga Jayamaha commented

2020-06-03 20:50:27 +02:00

@iss I have removed some unwanted models from the previous file and attached a simpler file. Also reduced the number of steps for developers to reproduce it by attaching a closer to complete .blend file.
However if i try to recreate this by remodeling everything from scratch, sometimes it works fine and sometimes not.
Thanks!

@iss I have removed some unwanted models from the previous file and attached a simpler file. Also reduced the number of steps for developers to reproduce it by attaching a closer to complete .blend file. However if i try to recreate this by remodeling everything from scratch, sometimes it works fine and sometimes not. Thanks!

Richard Antalik commented

2020-06-04 10:36:33 +02:00

Changed status from 'Needs Triage' to: 'Archived'

Richard Antalik closed this issue

2020-06-04 10:36:33 +02:00

Richard Antalik self-assigned this 2020-06-04 10:36:33 +02:00

Richard Antalik commented

2020-06-04 10:36:33 +02:00

Thanks for new files. I have only now looked at console and saw that there are dependency cycles. You need to resolve these, otherwise simulations won't work correctly.

Dependency cycle detected:
  SCScene/Transform Component/RIGIDBODY_SIM() depends on
  OBConstraint/Transform Component/TRANSFORM_FINAL() via 'RigidBodyConstraint Transform -> RB Simulation'
  OBConstraint/Transform Component/TRANSFORM_SIMULATION_INIT() via 'Simulation -> Final Transform'
  OBConstraint/Transform Component/TRANSFORM_EVAL() via 'Transform Eval -> Simulation Init'
  OBConstraint/Transform Component/TRANSFORM_PARENT() via 'Eval'
  OBConstraint/Transform Component/TRANSFORM_LOCAL() via 'ObLocal -> ObParent'
  OBConstraint/Transform Component/TRANSFORM_INIT() via 'Transform Init'
  OBConnector/Transform Component/TRANSFORM_FINAL() via 'Parent'
  OBConnector/Transform Component/RIGIDBODY_TRANSFORM_COPY() via 'Rigidbody Sync -> Transform Final'
  SCScene/Transform Component/RIGIDBODY_SIM() via 'Rigidbody Sim Eval -> RBO Sync'
Detected 2 dependency cycles

Thanks for new files. I have only now looked at console and saw that there are dependency cycles. You need to resolve these, otherwise simulations won't work correctly. ``` Dependency cycle detected: SCScene/Transform Component/RIGIDBODY_SIM() depends on OBConstraint/Transform Component/TRANSFORM_FINAL() via 'RigidBodyConstraint Transform -> RB Simulation' OBConstraint/Transform Component/TRANSFORM_SIMULATION_INIT() via 'Simulation -> Final Transform' OBConstraint/Transform Component/TRANSFORM_EVAL() via 'Transform Eval -> Simulation Init' OBConstraint/Transform Component/TRANSFORM_PARENT() via 'Eval' OBConstraint/Transform Component/TRANSFORM_LOCAL() via 'ObLocal -> ObParent' OBConstraint/Transform Component/TRANSFORM_INIT() via 'Transform Init' OBConnector/Transform Component/TRANSFORM_FINAL() via 'Parent' OBConnector/Transform Component/RIGIDBODY_TRANSFORM_COPY() via 'Rigidbody Sync -> Transform Final' SCScene/Transform Component/RIGIDBODY_SIM() via 'Rigidbody Sim Eval -> RBO Sync' Detected 2 dependency cycles ```

Maduranga Jayamaha commented

2020-06-06 19:47:13 +02:00

Changed status from 'Archived' to: 'Resolved'

Maduranga Jayamaha commented

2020-06-06 19:47:30 +02:00

Changed status from 'Resolved' to: 'Archived'

Maduranga Jayamaha commented

2020-06-06 20:03:10 +02:00

Hi @iss,
I managed to remove the dependency cycles and still recreate the issue. However since it was not possible to reopen this task I created a new task which is https://developer.blender.org/T77529. Hope that it is OK to enter new task.
Thank you!

Hi @iss, I managed to remove the dependency cycles and still recreate the issue. However since it was not possible to reopen this task I created a new task which is https://developer.blender.org/T77529. Hope that it is OK to enter new task. Thank you!

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cloth object connected to 2 rigid bodies does not animate correctly #77190