Apply scale on armature breaks position of child elements with relationship 'Bone' #91101

New Issue

Astralite Heart · 2021-09-01T03:48:42+02:00

Astralite Heart commented

2021-09-01 03:48:42 +02:00

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 3090/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 471.68

Blender Version
Broken: version: 2.93.1, branch: master, commit date: 2021-06-22 05:57, hash: 1b8d33b18c
Also Broken: blender-2.93.4-candidate+v293.7ec351c0d531-windows.amd64-release
Worked: Never (2.80+)

Short description of error
If I have an armature with non (1,1,1) scale and if I create an object that is parented to one of the armature bones, applying the scale to the armature moves the object.

If I then select my arrow/cube and remove the 'Parent Bone', it is aligned correctly again, if I then put the 'Parent Bone' bone back, the arrow/cube is moved to a completely new position.

I can also see the following error in terminal when I unparent the bone (I don't think this is relevant and clearing the bone always prints this, but just in case)

add_relation(Bone Parent) - Could not find op_from (ComponentKey(OBArmature, BONE))
add_relation(Bone Parent) - Failed, but op_to (ComponentKey(OBEmpty, TRANSFORM)) was ok
ERROR (bke.object): C:\Users\blender\git\blender-v293\blender.git\source\blender\blenkernel\intern\object.c:3330 ob_parbone: Object Empty with Bone parent: bone  doesn't exist

My theory is that Blender is trying to reposition the object without taking the bone parent into consideration.

I've recorded a small video to illustrate: https://www.youtube.com/watch?v=BGNckTOfBQQ

I was also able to create a script that fixes the position by detaching the parent and reattaching with keep_transform (also note the commented out line)

import bpy

print ('Bone fixer')
for obj in bpy.data.objects:
    if (obj.parent_type == 'BONE' and obj.parent_bone):
        bpy.ops.object.select_all(action='DESELECT')
        
        print (f'Parent={obj.parent} parent_={obj.parent_type} parent_bone={obj.parent_bone}')
        print (obj.name, obj.scale, obj.location, obj.rotation_euler)
        
        # obj.parent_bone = obj.parent_bone # This line should not have any effect but it does move the object to a new position

        parent_bone = obj.parent_bone
        obj.parent_bone = '' # We are now correctly positioned but not parented                        

        obj.select_set(state=True)
        obj.parent.select_set(state=True)
        obj.parent.data.bones[parent_bone].select = True
        bpy.ops.object.parent_set(type='BONE', keep_transform=True)

Exact steps for others to reproduce the error
Based on the default startup or an attached .blend file (as simple as possible).

test.blend

Create armature ('Armature') and set a non 1,1,1 scale
Add bones to armature
Create a new object (I tried empty/arrow or cube)
Set relationship on the cube as parent = 'Armature', Parent Type = Bone, Parent Bone = 'Bone.X' (last bone in the sample file)
(^ Already done in sample file)
Select armature and "Apply scale"

Expected - the empty remains at the 'end' of the bone
Observed - the empty is moved to a new location (I am unsure what is the logic)

**System Information** Operating system: Windows-10-10.0.19041-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 3090/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 471.68 **Blender Version** Broken: version: 2.93.1, branch: master, commit date: 2021-06-22 05:57, hash: `1b8d33b18c` Also Broken: blender-2.93.4-candidate+v293.7ec351c0d531-windows.amd64-release Worked: Never (2.80+) **Short description of error** If I have an armature with non (1,1,1) scale and if I create an object that is parented to one of the armature bones, applying the scale to the armature moves the object. If I then select my arrow/cube and remove the 'Parent Bone', it is aligned correctly again, if I then put the 'Parent Bone' bone back, the arrow/cube is moved to a completely new position. I can also see the following error in terminal when I unparent the bone (I don't think this is relevant and clearing the bone always prints this, but just in case) ``` add_relation(Bone Parent) - Could not find op_from (ComponentKey(OBArmature, BONE)) add_relation(Bone Parent) - Failed, but op_to (ComponentKey(OBEmpty, TRANSFORM)) was ok ERROR (bke.object): C:\Users\blender\git\blender-v293\blender.git\source\blender\blenkernel\intern\object.c:3330 ob_parbone: Object Empty with Bone parent: bone doesn't exist ``` My theory is that Blender is trying to reposition the object without taking the bone parent into consideration. I've recorded a small video to illustrate: https://www.youtube.com/watch?v=BGNckTOfBQQ I was also able to create a script that fixes the position by detaching the parent and reattaching with keep_transform (also note the commented out line) ``` import bpy print ('Bone fixer') for obj in bpy.data.objects: if (obj.parent_type == 'BONE' and obj.parent_bone): bpy.ops.object.select_all(action='DESELECT') print (f'Parent={obj.parent} parent_={obj.parent_type} parent_bone={obj.parent_bone}') print (obj.name, obj.scale, obj.location, obj.rotation_euler) # obj.parent_bone = obj.parent_bone # This line should not have any effect but it does move the object to a new position parent_bone = obj.parent_bone obj.parent_bone = '' # We are now correctly positioned but not parented obj.select_set(state=True) obj.parent.select_set(state=True) obj.parent.data.bones[parent_bone].select = True bpy.ops.object.parent_set(type='BONE', keep_transform=True) ``` **Exact steps for others to reproduce the error** Based on the default startup or an attached .blend file (as simple as possible). [test.blend](https://archive.blender.org/developer/F10359147/test.blend) 1. Create armature ('Armature') and set a non 1,1,1 scale 2. Add bones to armature 3. Create a new object (I tried empty/arrow or cube) 4. Set relationship on the cube as parent = 'Armature', Parent Type = Bone, Parent Bone = 'Bone.X' (last bone in the sample file) (^ Already done in sample file) 5. Select armature and "Apply scale" Expected - the empty remains at the 'end' of the bone Observed - the empty is moved to a new location (I am unsure what is the logic)

Astralite Heart commented

2021-09-01 03:48:42 +02:00

Added subscriber: @Astralite-Heart

Richard Antalik commented

2021-09-01 05:06:40 +02:00

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

blender-admin commented

2021-09-03 12:17:00 +02:00

This issue was referenced by a45dd52cf0

This issue was referenced by a45dd52cf0bbdc0ff362681a4836385c8154c70d

Philipp Oeser commented

2021-09-03 12:21:24 +02:00

Added subscriber: @lichtwerk

Philipp Oeser commented

2021-09-03 12:21:24 +02:00

I can also see the following error in terminal when I unparent the bone (I don't think this is relevant and clearing the bone always prints this, but just in case)

This should be fixed by D12389: Depsgraph: skip parentbone relation if bone prop is empty

> I can also see the following error in terminal when I unparent the bone (I don't think this is relevant and clearing the bone always prints this, but just in case) This should be fixed by [D12389: Depsgraph: skip parentbone relation if bone prop is empty](https://archive.blender.org/developer/D12389)

blender-admin commented

2021-09-03 17:16:42 +02:00

This issue was referenced by 235655ee0d

This issue was referenced by 235655ee0d0634db9150b1dc266e3a3b35c491e4

Philipp Oeser removed the

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Apply scale on armature breaks position of child elements with relationship 'Bone' #91101