Unable to update mesh vertex properties via Python when mesh is influenced by armature #39747

New Issue

solarlune · 2014-04-15T17:40:32+02:00

solarlune commented

2014-04-15 17:40:32 +02:00

System Information

Windows 7 64-bit
AMD Radeon HD 7700

Blender Version

Broken: Blender 2.7 3cf39fc
Worked: Unsure if it ever worked correctly

Short description of error

I reported this bug already before the bug tracker switched sites, but I guess it was lost in the move. So here's the report again.

Basically, if an object has an armature modifier on it and is parented to an armature (to be deformed by an armature), you can no longer alter its mesh's vertex properties by Python. They update in Python, but the changes aren't applied visually. I would understand if you were just unable to update a vertex's position and perhaps its normals, as those properties are being altered by the armature.

However, I think one should be able to alter the vertex's UV values and color properties (as well as any others that they wish), if possible, since the armature shouldn't have any influence on these properties.

Exact steps for others to reproduce the error

Just press P to start the game engine and see the cube sit there, unmoving (the bug).
Select and delete the armature.
Press P to start the game engine and see the vertices of the cube move along slowly, quickly altering their colors and UV values (the correct behavior).

ArmatureParentedUpdateBug.blend

**System Information** Windows 7 64-bit AMD Radeon HD 7700 **Blender Version** Broken: Blender 2.7 3cf39fc Worked: Unsure if it ever worked correctly **Short description of error** I reported this bug already before the bug tracker switched sites, but I guess it was lost in the move. So here's the report again. Basically, if an object has an armature modifier on it and is parented to an armature (to be deformed by an armature), you can no longer alter its mesh's vertex properties by Python. They update in Python, but the changes aren't applied visually. I would understand if you were just unable to update a vertex's position and perhaps its normals, as those properties are being altered by the armature. However, I think one should be able to alter the vertex's UV values and color properties (as well as any others that they wish), if possible, since the armature shouldn't have any influence on these properties. **Exact steps for others to reproduce the error** 1) Just press P to start the game engine and see the cube sit there, unmoving (the bug). 2) Select and delete the armature. 3) Press P to start the game engine and see the vertices of the cube move along slowly, quickly altering their colors and UV values (the correct behavior). [ArmatureParentedUpdateBug.blend](https://archive.blender.org/developer/F84952/ArmatureParentedUpdateBug.blend)

solarlune commented

2014-04-15 17:40:32 +02:00

Changed status to: 'Open'

solarlune commented

2014-04-15 17:40:32 +02:00

Added subscriber: @solarlune

blender-admin commented

2014-04-15 17:40:32 +02:00

#19876 was marked as duplicate of this issue

Daniel Stokes commented

2014-04-16 05:56:19 +02:00

Added subscriber: @kupoman

Daniel Stokes commented

2014-04-16 05:56:19 +02:00

Can confirm the problem. Deleting the modifier works as well.

Just a guess without looking at the code, could be that the armature deformer is using Blender data instead of the BGE data.

Can confirm the problem. Deleting the modifier works as well. Just a guess without looking at the code, could be that the armature deformer is using Blender data instead of the BGE data.

Mitchell Stokes commented

2014-04-16 08:25:14 +02:00

Added subscriber: @Moguri

Mitchell Stokes commented

2014-04-16 08:25:14 +02:00

This looks a lot like #32182. Is this the other report you were trying to find?

solarlune commented

2014-04-16 09:16:04 +02:00

No, I don't believe it is, as this sounds like a slightly different issue. Thanks for looking, nonetheless.

EDIT: Ah, that last comment I made in the other ticket about the armature sounds like exactly the same issue. Maybe this is the ticket I was talking about. Thanks again for looking, Moguri.

No, I don't believe it is, as this sounds like a slightly different issue. Thanks for looking, nonetheless. EDIT: Ah, that last comment I made in the other ticket about the armature sounds like exactly the same issue. Maybe this is the ticket I was talking about. Thanks again for looking, Moguri.

Mitchell Stokes commented

2014-05-13 01:28:21 +02:00

The BL_SkinDeformer (this controls mesh skinning for armatures) creates a copy display array since BL_SkinDeformer::ShareVertexArray() returns false (see RAS_MeshSlot::SetDeformer()). Changing the return to true solves most of this bug (position and normals are grabbed from the original blender mesh, and not the BGE meshes, so changing those through KX_Mesh/VertexProxy doesn't change the input position and normals to BL_SkinDeformer, thus the output doesn't change). However, I am unsure how to get the KX_Mesh/VertexProxy to grab the right vertex/display array, since I'm not even sure which one is the "right" one. Especially since it seems a mesh can have multiple representations of a vertex. In other words, our BGE meshes are an absolute mess. I'll probably either have to design a very clever (and probably equally ugly) hack to get this working, or wait until we (hopefully, eventually) rewrite the rasterizer.