animations: convert skinning weights from unorm8x4 to float32x4

[mockersf]

Objective

• Fixes part of Bevy panics with certain skinned meshes #9021

Solution

• Joint mesh are in format Unorm8x4 in some gltf file, but Bevy expects a Float32x4. Converts them. Also converts Unorm16x4
• According to gltf spec: https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html#skinned-mesh-attributes

WEIGHTS_n: float, or normalized unsigned byte, or normalized unsigned short

[nicopap]

This doesn't fix it in the case of my modified snow model.

It's 24MB here (sorry Microsoft for eating your storage space 🙏):

snow_mini.zip

There is a lot of mess in the file, but yeah bevy still shouldn't panic with a cryptic error message.

[mockersf]

There is a lot of mess in the file, but yeah bevy still shouldn't panic with a cryptic error message.

As the error obviously says for your model, it has too many joints (1484, Bevy supports up to 256 joints)
the error:

thread '<unnamed>' panicked at 'wgpu error: Validation Error

Caused by:
    In a RenderPass
      note: encoder = `<CommandBuffer-(0, 33, Metal)>`
    In a draw command, indexed:true indirect:false
      note: render pipeline = `<RenderPipeline-(5, 1, Metal)>`
    The pipeline layout, associated with the current render pipeline, contains a bind group layout at index 2 which is incompatible with the bind group layout associated with the bind group at 2

So... obvious. If I raise the MAX_JOINTS here:

bevy/crates/bevy_pbr/src/render/mesh.rs

Line 54 in 4209819

const MAX_JOINTS: usize = 256;

I get something that doesn't crash, but still not what you expect...

So this PR doesn't fix your issue, but it still need to be done to follow the GLTF spec

[eastside]

I can confirm that this solved an issue importing a .gltf generated from Unreal Engine for me! Looks great!

[mockersf]

merging as trivial as this PR follows glTF spec without introducing new concept to do so