[Feature] glTF animation import

[vmarcella]

Overview

Extend the glTF loader to import skeletal animations, bones, and skinning data.

Current State

No response

Scope

Goals:

• Import skeleton/joints from glTF
• Import animation clips
• Import skin data (weights, indices)
• Support multiple animations per file

Non-Goals:

• Morph target animation
• Animation compression

Proposed API

pub struct GltfAsset {
  pub meshes: Vec<GltfMesh>,
  pub materials: Vec<GltfMaterial>,
  pub textures: Vec<ImageAsset>,
  pub skeletons: Vec<Skeleton>,
  pub animations: Vec<SkeletalAnimationClip>,
  pub skins: Vec<GltfSkin>,
}

pub struct GltfSkin {
  pub skeleton_index: usize,
  pub joint_indices: Vec<[u8; 4]>,
  pub joint_weights: Vec<[f32; 4]>,
}

Acceptance Criteria

• Skeleton extracted from glTF joints
• Animation clips extracted with correct timing
• Skin weights and indices extracted
• Works with standard glTF test models
• Example loading and playing animated model

Affected Crates

lambda-rs

Notes

• glTF animation targets node transforms
• Map nodes to bones correctly
• Test with Khronos glTF samples