problem with parenting GreasePencil Layer to armature Bone #82793

New Issue

mchaptel · 2020-11-17T16:29:37+01:00

mchaptel commented

2020-11-17 16:29:37 +01:00

System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce GTX 960/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 432.00

Blender Version
Broken: version: 2.91.0 Beta, branch: master, commit date: 2020-11-16 21:13, hash: 906ff7b8fe
Worked: 2.79 ?

Short description of error
When parenting a GP layer to an animated bone, an offset seems to occur.

Exact steps for others to reproduce the error

Open any of the attached files
In pose mode, transform the bone that has parenting with the layer of the Grese pencil object
Parenting a sphere to the bone DEF-spine.006 works as expected.
However, the same parenting applied to the grease pencil layer does not follow the sphere.
Note that parenting the layer to the sphere does not take into account the sphere's own parenting.

Simple file:
ex_parentage_broken_simple.blend

Complex file:
ex_parentage_broken.blend

**System Information** Operating system: Windows-10-10.0.18362-SP0 64 Bits Graphics card: GeForce GTX 960/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 432.00 **Blender Version** Broken: version: 2.91.0 Beta, branch: master, commit date: 2020-11-16 21:13, hash: `906ff7b8fe` Worked: 2.79 ? **Short description of error** When parenting a GP layer to an animated bone, an offset seems to occur. ![bug_gp_parenting_frame1.PNG](https://archive.blender.org/developer/F9312016/bug_gp_parenting_frame1.PNG) ![bug_gp_parenting_frame13.PNG](https://archive.blender.org/developer/F9312015/bug_gp_parenting_frame13.PNG) ![bug_gp_parenting_setup.PNG](https://archive.blender.org/developer/F9312014/bug_gp_parenting_setup.PNG) **Exact steps for others to reproduce the error** - Open any of the attached files - In pose mode, transform the bone that has parenting with the layer of the Grese pencil object Parenting a sphere to the bone DEF-spine.006 works as expected. However, the same parenting applied to the grease pencil layer does not follow the sphere. Note that parenting the layer to the sphere does not take into account the sphere's own parenting. Simple file: [ex_parentage_broken_simple.blend](https://archive.blender.org/developer/F9550405/ex_parentage_broken_simple.blend) Complex file: [ex_parentage_broken.blend](https://archive.blender.org/developer/F9312026/ex_parentage_broken.blend)

mchaptel commented

2020-11-17 16:29:37 +01:00

Added subscriber: @Awk

Germano Cavalcante commented

2020-11-18 21:47:39 +01:00

Added subscriber: @mano-wii

Germano Cavalcante commented

2020-11-18 21:47:39 +01:00

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

Germano Cavalcante commented

2020-11-18 21:47:39 +01:00

Can you simplify the .blend file further?
Unlike the sphere, the Grease Pencil object does not have a parent:

Both do not have similar configurations so it is not strange that they behave differently.

Can you simplify the .blend file further? Unlike the sphere, the Grease Pencil object does not have a parent: ![image.png](https://archive.blender.org/developer/F9319097/image.png) Both do not have similar configurations so it is not strange that they behave differently.

mchaptel commented

2020-11-19 12:22:02 +01:00

Hello,

I don't want to parent the grease pencil object, but the single layer, as I may want to parent different layers to different bones. Having a separate grease pencil object for each bone would be too heavy for my workflow which is based on this feature that used to work in 2.79.

However, the relations of the layer itself and the sphere's are the same, as shown in the screen capture I posted above. This information is only visible while the grease pencil object is selected, in the grease pencil layers window.

I'm afraid I can't simplify the blend further because while trying with a simpler file, I could not replicate the bug.

Hello, I don't want to parent the grease pencil object, but the single layer, as I may want to parent different layers to different bones. Having a separate grease pencil object for each bone would be too heavy for my workflow which is based on this feature that used to work in 2.79. However, the relations of the layer itself and the sphere's are the same, as shown in the screen capture I posted above. This information is only visible while the grease pencil object is selected, in the grease pencil layers window. I'm afraid I can't simplify the blend further because while trying with a simpler file, I could not replicate the bug.

mchaptel commented

2020-11-25 18:30:58 +01:00

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

Germano Cavalcante commented

2021-01-04 16:24:09 +01:00

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

Germano Cavalcante commented

2021-01-04 16:29:58 +01:00

Added subscriber: @filedescriptor

Germano Cavalcante commented

2021-01-04 16:29:58 +01:00

Thanks @filedescriptor for providing a simplified file that helps confirm the problem and will help developers to detect and fix the bug.
Perhaps it is by design or a limitation that the transformation matrix of the Grease Pencil object is not considered in the parenting of layers with bones.
But my first impression is that it is a bug, so I am confirming it.

Thanks @filedescriptor for providing a simplified file that helps confirm the problem and will help developers to detect and fix the bug. Perhaps it is by design or a limitation that the transformation matrix of the Grease Pencil object is not considered in the parenting of layers with bones. But my first impression is that it is a bug, so I am confirming it.

Antonio Vazquez commented

2021-01-04 17:02:48 +01:00

Added subscriber: @antoniov

Antonio Vazquez commented

2021-01-04 17:02:48 +01:00

Actually the layer parenting is not considering the GPencil object transform. Layer parenting is a special overrride of the parenting and disable any object parenting. If we change that, we could break a lot of files because this is how works, since several versions, so not sure we must change that.

mchaptel commented

2021-01-04 21:25:26 +01:00

It seems to me in our recent tests that applying the transform to the grease pencil object and resetting it to a neutral transform fixed the problem.

If that's the case, then most likely all grease pencil objects in files making use of this feature will have a neutral transform otherwise parenting is unusable.

In that sense, it feels like changing this behavior should be compatible with any file making use of this feature.

It seems to me in our recent tests that applying the transform to the grease pencil object and resetting it to a neutral transform fixed the problem. If that's the case, then most likely all grease pencil objects in files making use of this feature will have a neutral transform otherwise parenting is unusable. In that sense, it feels like changing this behavior should be compatible with any file making use of this feature.

Antonio Vazquez commented

2021-01-04 22:10:47 +01:00

@Awk Yes, if you move the gpencil object to origin the problem is fixed... I will think about this and study the implications of the change to verify if we can do it or it's better keep it as a limitation.

mchaptel commented

2021-01-05 01:18:26 +01:00

Thank you, I appreciate this.

As I said before, from my testing the feature does not work currently, as layers from a gp object that isn't in neutral transform, parented to bones just do not follow what they are parented to, it's very unpredictable.

So to me there aren't really any drawbacks to implementing a complete override for the layers that would take into account the transform on the GP object so that they can follow the bones properly.

I think in fact not fixing it could be very detrimental to the ability to rig greasepencil designs, and that would be a shame.

Thank you, I appreciate this. As I said before, from my testing the feature does not work currently, as layers from a gp object that isn't in neutral transform, parented to bones just do not follow what they are parented to, it's very unpredictable. So to me there aren't really any drawbacks to implementing a complete override for the layers that would take into account the transform on the GP object so that they can follow the bones properly. I think in fact not fixing it could be very detrimental to the ability to rig greasepencil designs, and that would be a shame.

Falk David commented

2021-01-05 09:56:07 +01:00

I can confirm that the problem is the GP object origin. If I reset the origin to the world center, the parenting looks good. I don't see an issue with fixing this and breaking older files. As @Awk pointed out, the only way to use layer parenting at the moment is to have the origin at the world center which would not be affected by a patch.

Antonio Vazquez self-assigned this 2021-01-05 10:17:59 +01:00

Henrik D. commented

2021-09-17 16:04:57 +02:00

Added subscriber: @HDMaster84