Separating mesh parts breaks shape keys #71865

New Issue

Takuya Sawatari · 2019-11-24T19:34:24+01:00

Takuya Sawatari commented

2019-11-24 19:34:24 +01:00

System Information
Operating system: Linux-5.0.0-36-generic-x86_64-with-debian-buster-sid 64 Bits
Graphics card: GeForce GTX 1060 6GB/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 430.50

Blender Version
Broken: version: 2.81 (sub 16), branch: master, commit date: 2019-11-20 14:27, hash: 26bd5ebd42
Worked: 2.80

Short description of error
Separating mesh parts to a new object breaks the original object's shape keys.

Exact steps for others to reproduce the error

Create a UV sphere object.
Enter edit mode.
Duplicate the sphere mesh so that there are 4 spheres in the mesh object.
Create a "Basis" shape key + one extra shape key "Key 1".
Independently scale the middle 2 spheres a bit bigger in the "Key 1" shapekey.
Select the mesh parts of the lower 2 spheres, press P and separate the selection.
Enter object mode and select the old mesh object with the top 2 spheres.
Enable the "Key 1" shapekey.
Notice the incorrect deformation.

Test file:
blender_2_81_shape_key_bug4.blend

This also happens with complex project files which worked fine in Blender 2.80. Loading the test file in 2.80 and performing the procedure causes no issues.

**System Information** Operating system: Linux-5.0.0-36-generic-x86_64-with-debian-buster-sid 64 Bits Graphics card: GeForce GTX 1060 6GB/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 430.50 **Blender Version** Broken: version: 2.81 (sub 16), branch: master, commit date: 2019-11-20 14:27, hash: `26bd5ebd42` Worked: 2.80 **Short description of error** Separating mesh parts to a new object breaks the original object's shape keys. **Exact steps for others to reproduce the error** 1. Create a UV sphere object. 2. Enter edit mode. 3. Duplicate the sphere mesh so that there are 4 spheres in the mesh object. 4. Create a "Basis" shape key + one extra shape key "Key 1". 5. Independently scale the middle 2 spheres a bit bigger in the "Key 1" shapekey. 6. Select the mesh parts of the lower 2 spheres, press P and separate the selection. 7. Enter object mode and select the old mesh object with the top 2 spheres. 8. Enable the "Key 1" shapekey. 9. Notice the incorrect deformation. Test file: [blender_2_81_shape_key_bug4.blend](https://archive.blender.org/developer/F8162440/blender_2_81_shape_key_bug4.blend) This also happens with complex project files which worked fine in Blender 2.80. Loading the test file in 2.80 and performing the procedure causes no issues.

Takuya Sawatari commented

2019-11-24 19:34:24 +01:00

Added subscriber: @Takuya

Philipp Oeser commented

2019-11-25 10:50:48 +01:00

Added subscriber: @lichtwerk

Philipp Oeser commented

2019-11-25 10:50:48 +01:00

Confirmed, checking...

Philipp Oeser commented

2019-11-25 11:48:52 +01:00

Added subscriber: @ideasman42

Philipp Oeser commented

2019-11-25 11:48:52 +01:00

This looks like it is caused by 79b703bb63.

@ideasman42 : mind checking?

This looks like it is caused by 79b703bb63. @ideasman42 : mind checking?

Campbell Barton self-assigned this 2019-11-25 11:52:29 +01:00

Campbell Barton commented

2019-11-27 18:05:04 +01:00

The error has been in Blender since 2.7x, probably going back much earlier.

While 79b703bb63 introduced a call to flush edits from edit-mode to object mode, saving the file will cause a flush too, so it's possible to reproduce the error in older releases too.

Although in my tests asan is reporting bad memory access and crashing (not just failing to update the shape keys).

Edit, this no longer crashes, however the issue remains with the shape-key not properly updating: 34902f2008

The following steps cause invalid memory access on a mesh with shape keys:

Create a new file containing a mesh with a shape key.
Enter edit mode.
Select half the mesh.
Separate the selection.
Save the file.
Exit edit-mode (invalid memory access).

While the crash can be fixed by checking the index range, there will still be an error updating shape-keys.

The problem is that the edit-meshes original indices aren't updated when flushing the changes back to the shape-key (when saving the file).
Existing edit-mode a second time tries to access indices from the original un-separated mesh and fails.

Here is a test that shows the error, run this with --factory-startup.

import bpy

bpy.ops.mesh.primitive_uv_sphere_add()
bpy.ops.object.mode_set(mode='EDIT')
bpy.ops.mesh.select_all(action='DESELECT')
bpy.ops.object.mode_set(mode='OBJECT')

a = bpy.context.object
bpy.context.object.location.x += 2
bpy.ops.mesh.primitive_uv_sphere_add()
b = bpy.context.object
a.select_set(1)
b.select_set(1)
bpy.ops.object.join()

bpy.ops.object.shape_key_add(from_mix=False)
bpy.ops.object.shape_key_add(from_mix=False)
bpy.context.object.active_shape_key_index = 0


- -----------------------------
- Main setup done, now redo bug
#
- These lines can run in a loop.

bpy.ops.object.mode_set(mode='EDIT')
bpy.ops.mesh.separate(type='SELECTED')

#bpy.ops.wm.save_mainfile() # Also causes issue.
bpy.context.object.update_from_editmode()

bpy.ops.mesh.select_all(action='SELECT')
bpy.ops.object.mode_set(mode='OBJECT')
bpy.ops.object.join()

The error has been in Blender since 2.7x, probably going back much earlier. While 79b703bb63 introduced a call to flush edits from edit-mode to object mode, saving the file will cause a flush too, so it's possible to reproduce the error in older releases too. Although in my tests asan is reporting bad memory access and crashing (not just failing to update the shape keys). ---- Edit, this no longer crashes, however the issue remains with the shape-key not properly updating: 34902f2008 ---- The following steps cause invalid memory access on a mesh with shape keys: - Create a new file containing a mesh with a shape key. - Enter edit mode. - Select half the mesh. - Separate the selection. - Save the file. - Exit edit-mode *(invalid memory access)*. While the crash can be fixed by checking the index range, there will still be an error updating shape-keys. The problem is that the edit-meshes original indices aren't updated when flushing the changes back to the shape-key (when saving the file). Existing edit-mode a second time tries to access indices from the original un-separated mesh and fails. ---- Here is a test that shows the error, run this with `--factory-startup`. ``` import bpy bpy.ops.mesh.primitive_uv_sphere_add() bpy.ops.object.mode_set(mode='EDIT') bpy.ops.mesh.select_all(action='DESELECT') bpy.ops.object.mode_set(mode='OBJECT') a = bpy.context.object bpy.context.object.location.x += 2 bpy.ops.mesh.primitive_uv_sphere_add() b = bpy.context.object a.select_set(1) b.select_set(1) bpy.ops.object.join() bpy.ops.object.shape_key_add(from_mix=False) bpy.ops.object.shape_key_add(from_mix=False) bpy.context.object.active_shape_key_index = 0 - ----------------------------- - Main setup done, now redo bug # - These lines can run in a loop. bpy.ops.object.mode_set(mode='EDIT') bpy.ops.mesh.separate(type='SELECTED') #bpy.ops.wm.save_mainfile() # Also causes issue. bpy.context.object.update_from_editmode() bpy.ops.mesh.select_all(action='SELECT') bpy.ops.object.mode_set(mode='OBJECT') bpy.ops.object.join() ```

blender-admin commented

2019-11-27 20:12:17 +01:00

This issue was referenced by 7711231838

This issue was referenced by 7711231838e726055c6690757f3799dff90bfd96

Campbell Barton commented

2019-11-27 20:45:25 +01:00

Changed status from 'Open' to: 'Resolved'

Campbell Barton closed this issue

2019-11-27 20:45:25 +01:00

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Separating mesh parts breaks shape keys #71865