TinyGltfImporter: Import Weights and JointIds mesh attributes

[Squareys]

Hi @mosra !

Building on top of mosra/magnum#441, here's the import of the new mesh attributes in TinyGltfImporter.

Best,
Jonathan

TODO

• Docs: Advertise support
• Tests
• What are "skins"?
• Is this sufficient to import skinned mesh animations?

[Squareys]

From gitter to archive here:

It appears that in addition to the Skin Data, we will need to import some form of "Skin" or "Skeleton", which requires extension of the Trade:: Apis.
I.e. this could be done with SkeletonData / SkinData or a Trade::SkinnedMeshObjectData
There are inverseBindMatrices that are stored per Bone in there (Some Matrix accessor in gltf), a reference to the root node and the nodes that are used as bones/joints
Since ObjectType::Light will redirect to LightData, I assume we'd have ObjectType::SkinnedMesh and redirect to skin, mesh and possibly nodes of the skeleton

[mosra]

TODO for testing: the code relies on the attributes being sorted (so JOINTS_0 before JOINTS_1) and without gaps. I think sorting is ensured implicitly due to how JSON dict data is stored, but the gaps need to be checked.

[mosra]

Suggested change

	if(!(accessor.componentType == TINYGLTF_COMPONENT_TYPE_UNSIGNED_BYTE) &&
	!(accessor.componentType == TINYGLTF_COMPONENT_TYPE_UNSIGNED_SHORT)) {
	if(!(accessor.componentType == TINYGLTF_COMPONENT_TYPE_UNSIGNED_BYTE && !accessor.normalized) &&
	!(accessor.componentType == TINYGLTF_COMPONENT_TYPE_UNSIGNED_SHORT && !accessor.normalized)) {

IDs can't be normalized. Also needs a test ;)

[mosra]

Huh, what's this, completely forgot this was even attempted in the old plugin 😆 Two complete plugin reimplementations later, this is done in GltfImporter in cf9c300.