More Than One Way to Skin a... Model.

Ommi

Hello once again!

I have successfully and happily imported a 3D model into a scene. It renders and animates correctly. One might be so bold as to say it is "working".

Super! The imported scene is nothing more than a Spatial containing a Skeleton and an AnimationPlayer. The Skeleton, in turn, contains a number of MeshInstances. Also super.

So far, all fine. Then somebody, possibly myself, had the idea of saving the MeshInstance's Mesh as a resource, in the hopes of creating some variance in the models by swapping around MeshInstances. As a test, saved a Mesh as a resource. Deleted the MeshInstance from the scene. Added a new MeshInstance. Assigned the Skeleton to it. Assigned the (previously saved) Mesh to it. And... it kinda displayed. Kinda. In the wrong spot, completely deformed, and fluttering around like a confused butterfly.

My guess (!) is the (lack) of an associated Skin. The imported MeshInstance all have a Skin property, which appears to bind the MeshInstance to the Skeleton. But I can't find anything on this Skin object. The documentation is, well, missing. Skeleton has a register_skin method, but no obvious way to get a Skin.

There is a Reddit post from a year ago suggesting that Skin property should just be left empty, and the Engine will calculate it at startup. It doesn't, and I'm not sure "at startup" helps me anyway.

And after all that, maybe my whole approach is completely misguided, and the whole Skin thing is just mistaken.

Any insights appreciated!

cybereality

This is called animation retargeting (if you want to look around) but is not supported in Godot 3.x. Some people have found clever work arounds, but it's rather complex. It will be supported in Godot 4.0, but I haven't checked to see if it works in the alpha yet.

Calinou

Animation retargeting is being worked on for Godot 4.0 here: https://github.com/godotengine/godot/pull/56902

It's not available in 4.0alpha1.

cybereality

Thanks for the insight as always, @Calinou

Ommi

Hm. I fear I'm either not understanding, explaining myself poorly, or possibly both.

Animation Retargeting, best I can tell from the linked PR and subsequent searching, seems to be the process of transitioning one Skeleton to another.

That's not my goal. At least, I don't think it is.

I've no wish to change the Skeleton, or its association with animations. The Skeleton can very much stay put.

Instead, I want to change a MeshInstance; removing an existing MeshInstance and adding a new one (with a different texture).

That is, "change the red striped shirt for a blue paisley shirt". (In code.)

cybereality

Animation retargeting doesn't change the skeleton. It is about applying the same animation to completely different meshes, different characters. In your case you might be able to just swap to a new material, provided the shape of the mesh does not change.

Ommi

Am I wholly misunderstanding the stated purpose of the linked PR then? It very much seems to be "change Skeleton A into Skeleton B".

Not that it really matters, as I think about it. At the end of the day, there appears to be no immediate (convenient) solution to my goals, but might be on the Godot horizon. I can content myself with that and move on. It isn't as if there is not pages of other tasks that need doing. Sadly.

I thank you both for your kind replies!

cybereality

Well the idea of animation retargeting is that two models will not have the exact same skeleton. Because one may be taller, or skinnier, or have different proportions, etc. But the same applies to sharing animation on different versions of the same model, because technically they are different models (for example, if they have different clothing or their mesh is otherwise not identical).

But you can change the material on a mesh easily with like 3 lines of code. This will work for simple low poly models to change their clothes (like have a different design on the shirt, but not a different shape). Or changing the skin color on a character. This is fairly simple and not a problem.