# Skeletal Meshes
## `SkinnedVertex`
[`SkinnedVertex`](../src/wgpu/skinned_mesh.rs) is [`Vertex`](./meshes.md#the-built-in-vertex-layout)'s 4 fields (position, UV, normal, tangent) plus per-vertex skinning data — up to 4 joint indices and matching weights:
```rust
use pebble::wgpu::skinned_mesh::SkinnedVertex;
let v = SkinnedVertex::new(
glam::Vec3::new(0.0, 0.6, 0.0),
glam::Vec2::ZERO,
glam::Vec3::Z,
glam::Vec4::new(1.0, 0.0, 0.0, 1.0),
[0, 1, 0, 0], // joint_indices — up to 4 joints this vertex is bound to
[0.7, 0.3, 0.0, 0.0], // joint_weights — matching weights, usually summing to ~1.0
);
```
`joint_indices` is `[u16; 4]` — glTF's own `JOINTS_n` accessor is spec-limited to 8/16-bit indices, so `u16` already covers every legal glTF skeleton losslessly, at half the bytes of `u32`.
`SkinnedVertex::layout()` occupies vertex buffer locations 0–3 (same meaning as [`Vertex`](./meshes.md#the-built-in-vertex-layout)'s own 0–3) and 8–9 — deliberately skipping 4–7, which [`InstanceVertex`](./meshes.md#the-built-in-vertex-layout) uses, so a skinned mesh can still be paired with per-instance data in one pipeline without either layout changing. On the WGSL side, declare `@location(8) joint_indices: vec4<u32>` and `@location(9) joint_weights: vec4<f32>` — every integer vertex format widens to `vec4<u32>` in the shader regardless of the source width.
## Building a skinned mesh
[`SkinnedMesh`](../src/wgpu/skinned_mesh.rs) is plain data with no public constructors of its own — the only way to build one is [`SkinnedMeshBuilder`](../src/wgpu/skinned_mesh.rs), same shape as [`MeshBuilder`](./meshes.md#building-a-mesh):
```rust
use pebble::wgpu::skinned_mesh::SkinnedMeshBuilder;
let mesh = SkinnedMeshBuilder::new(vertices, indices).build_asset("character", &mut skinned_meshes);
```
`.build_asset` returns a `Handle<SkinnedMesh>`, uploaded automatically through the same [asset pipeline](./the-asset-pipeline.md) as every other GPU resource. `Assets<SkinnedMesh>::get(handle)` returns `Option<&GPUSkinnedMesh>` — `vertex_buffer`/`index_buffer`/`index_count`, exactly like [`GPUMesh`](./meshes.md#building-a-mesh).
In practice you'll rarely hand-author `SkinnedVertex` data yourself — use [`SkinnedMeshBuilder::from_file`](./skeletons-and-animation.md#loading-from-gltf-with-skinnedmodelbuilder) to load a glTF file and get back a `LoadedSkinnedMesh` (mesh handles + a ready [`AnimationPlayer`](./skeletons-and-animation.md)) in one call. See [Skeletons and Animation](./skeletons-and-animation.md) for the full rendering loop.