Offset edge slide with 0 distance breaks pinned cloth simulation #85147

New Issue

Jesse · 2021-01-28T11:43:30+01:00

Jesse commented

2021-01-28 11:43:30 +01:00

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce RTX 3080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 460.89

Blender Version
Broken: version: 2.93.0 Alpha, branch: master, commit date: 2021-01-27 22:47, hash: df135b74fc

Short description of error
Objects with a cloth modifier that have a Pin Group assigned no longer simulate properly after performing the Offset Edge Slide operation with 0 distance in Edit Mode.

Afterwards, playing the scene and manually moving the cloth object shows that all vertices in the Pin Group that have weights less than 1.0 are stuck in place.

However, this does not happen if the Offset Edge Slide operation has at least a little bit of distance. This issue can also be fixed by sliding the newly generated edges a little bit, so they're not exactly overlapping the original edge this operation was performed on.

Exact steps for others to reproduce the error
From the default startup file:

Select the Cube and create a vertex group.
Assign a weight of 1.0 to at least one vertex and any other weight less than 1.0 to the other vertices.
Add the Cloth modifier to the Cube, and assign the vertex group from #2 to the Cloth simulation's Pin Group.
At this point, playing the scene in Object Mode while moving the Cube in the viewport shows expected cloth behavior.
Switch to Edit Mode on the Cube, and select any edge.
Perform an Offset Edge Slide on the selected edge, and immediately right click to apply the operation with 0 distance.

Now, playing the scene in Object Mode while moving the Cube in the viewport shows that all vertices that have a weight less than 1.0 are completely locked.

Alternatively, try to do #7 in the attached .blend file.
OffsetEdgeSlideBreaksPinnedCloth.blend

**System Information** Operating system: Windows-10-10.0.19041-SP0 64 Bits Graphics card: GeForce RTX 3080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 460.89 **Blender Version** Broken: version: 2.93.0 Alpha, branch: master, commit date: 2021-01-27 22:47, hash: `df135b74fc` **Short description of error** Objects with a cloth modifier that have a Pin Group assigned no longer simulate properly after performing the Offset Edge Slide operation with 0 distance in Edit Mode. Afterwards, playing the scene and manually moving the cloth object shows that all vertices in the Pin Group that have weights less than 1.0 are stuck in place. However, this does not happen if the Offset Edge Slide operation has at least a little bit of distance. This issue can also be fixed by sliding the newly generated edges a little bit, so they're not exactly overlapping the original edge this operation was performed on. ![image.png](https://archive.blender.org/developer/F9602308/image.png) ![image.png](https://archive.blender.org/developer/F9602311/image.png) **Exact steps for others to reproduce the error** From the default startup file: - Select the Cube and create a vertex group. - Assign a weight of 1.0 to at least one vertex and any other weight less than 1.0 to the other vertices. - Add the Cloth modifier to the Cube, and assign the vertex group from #2 to the Cloth simulation's Pin Group. - At this point, playing the scene in Object Mode while moving the Cube in the viewport shows expected cloth behavior. - Switch to Edit Mode on the Cube, and select any edge. - Perform an Offset Edge Slide on the selected edge, and immediately right click to apply the operation with 0 distance. # Now, playing the scene in Object Mode while moving the Cube in the viewport shows that all vertices that have a weight less than 1.0 are completely locked. Alternatively, try to do #7 in the attached .blend file. [OffsetEdgeSlideBreaksPinnedCloth.blend](https://archive.blender.org/developer/F9602297/OffsetEdgeSlideBreaksPinnedCloth.blend)

Jesse commented

2021-01-28 11:43:30 +01:00

Added subscriber: @Kaz-3

Robert Guetzkow commented

2021-01-28 12:03:18 +01:00

Added subscriber: @rjg

Robert Guetzkow commented

2021-01-28 12:03:18 +01:00

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

Robert Guetzkow commented

2021-01-28 12:03:18 +01:00

Has this worked properly in past versions of Blender? This seems to behave the same way all the way back to 2.80. That duplicate vertices / faces with zero area can cause issues in physics simulations seems more like a limitation rather than a bug to me and can be fixed by using Mesh > Clean Up > Merge By Distance.

Has this worked properly in past versions of Blender? This seems to behave the same way all the way back to 2.80. That duplicate vertices / faces with zero area can cause issues in physics simulations seems more like a limitation rather than a bug to me and can be fixed by using *Mesh > Clean Up > Merge By Distance*.

Jesse commented

2021-01-28 18:51:01 +01:00

Not that I'm aware of. 2.81 is the oldest version I was able to test this against, and the issue was still present there. I'm not sure if this causes issues for all physics simulations, but I didn't see any problems with soft body or hair dynamics.

In my case, I'd intentionally made the new edge loops on top of/very close to the original edge in order to get sharper boundaries for hair generation/interpolation on a mesh with a subsurf modifier.

Not that I'm aware of. 2.81 is the oldest version I was able to test this against, and the issue was still present there. I'm not sure if this causes issues for all physics simulations, but I didn't see any problems with soft body or hair dynamics. In my case, I'd intentionally made the new edge loops on top of/very close to the original edge in order to get sharper boundaries for hair generation/interpolation on a mesh with a subsurf modifier.

Robert Guetzkow commented

2021-02-20 23:21:19 +01:00

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

Robert Guetzkow closed this issue

2021-02-20 23:21:19 +01:00

Robert Guetzkow commented

2021-02-20 23:21:19 +01:00

I contacted the developer responsible for the cloth simulations and zero length edges must be avoided, otherwise it is expected to not function properly. Try to give them at least a bit of offset. I will have to close the ticket as this is the expected behavior/limitation of the simulation method and thus not considered a bug.

Sign in to join this conversation.

No Label

Download

What's New

Blender Studio

Manual

Developers Blog

Documentation

Benchmark

Blender Conference

Development Fund

One-time Donations

Offset edge slide with 0 distance breaks pinned cloth simulation #85147

Now, playing the scene in Object Mode while moving the Cube in the viewport shows that all vertices that have a weight less than 1.0 are completely locked.