Bone Attachment, Override Pose: Add the option to only affect Rotation or Position

[LordMcMutton]

Describe the project you are working on

The method with which I built my character armature made using Blend animations on the arms separate them from the body. It's too late to fix it, so the best option is messing with Bone Attachment 3D nodes to attach the potentially-floating arm bones to the shoulder bones.

Describe the problem or limitation you are having in your project

Using the various get_bone_pose_position/set_bone_pose_position settings and set_bone_parent are yielding no fruit, and we can't directly modify the skeleton, itself, so the Bone Attachment 3D nodes are a promising option. The trick is that I need to be able to override just the position of the bone without messing with its rotations.

Unfortunately, Override Pose is just a binary option with no further settings.

Describe the feature / enhancement and how it helps to overcome the problem or limitation

Override Pose could have the option to only modify the target Bone's Position or Rotation, as opposed to only both.

For my current predicament, it would allow me to keep the animations intact while fixing the detachment issue. I would use two Bone Attachment 3D nodes:
-One to attach to the floating Upper Arm bone, Override Pose, then set it to just modify Position
-One to attach to the proper Shoulder bone, this one without Override Pose
-Then write a script to attach the first Bone Attachment 3D to the second.
-Profit

For general use, it sounds like it would add a dimension of utility that doesn't currently exist in Godot's arsenal.

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

In terms of the UI, it could probably use the same setup that Remote Transform nodes use:

If this enhancement will not be used often, can it be worked around with a few lines of script?

It doesn't seem like it can. Working with individual Bones doesn't seem very intuitive or robust, unfortunately.

Is there a reason why this should be core and not an add-on in the asset library?

Enhances the functionality of an existing Node

[TokageItLab]

To begin with, BoneAttachment's Override should not be used often because it is too exclusionary. It forces all results to be overwritten, not just Animation but IK and any other modifiers.

We have left it in for compatibility, but I think the feature is probably a remnant from 3.x in order to move bones visually because there was no SkeletonEditor.

Working with individual Bones doesn't seem very intuitive or robust, unfortunately.

Also, I doubt that adding a filter to Override would make for an intuitive UI.

Indeed, it would look neat visually in the case where only position is allowed, but in the case where only rotation or only scale is allowed, the position of the bone and BoneAttachment are out of sync. It is odd as an "Attachment", therefore it should not be implemented.

If this kind of functionality is to be added, it should be in a new class that extends SkeletonModifier.

Creating a modifier like GlobalPoseSetter would be one way to do this. However, the use case of copying values from one particular bone to another should be solved by BoneConstraint (godotengine/godot#100984).

[LordMcMutton]

It looks like CopyTransformsModifier has the functionality I'm seeking with this Proposal- is that system a for-sure addition to the engine?

[TokageItLab]

It is not included in 4.4 because the new features have been frozen since now is beta (https://godotengine.org/article/dev-snapshot-godot-4-4-beta-1/), but will surely be added in 4.5.

[LordMcMutton]

In that case, I'll close this Proposal since an alternative system will cover it