# Objective
Memory usage optimisation
## Solution
`HashMap` and `HashSet`'s keys are immutable. So using mutable types
like `String`, `Vec<T>`, or `PathBuf` as a key is a waste of memory:
they have an extra `usize` for their capacity and may have spare
capacity.
This PR replaces these types by their immutable equivalents `Box<str>`,
`Box<[T]>`, and `Box<Path>`.
For more context, I recommend watching the [Use Arc Instead of
Vec](https://www.youtube.com/watch?v=A4cKi7PTJSs) video.
---------
Co-authored-by: James Liu <contact@jamessliu.com>
Conventionally, the second UV map (`TEXCOORD1`, `UV1`) is used for
lightmap UVs. This commit allows Bevy to import them, so that a custom
shader that applies lightmaps can use those UVs if desired.
Note that this doesn't actually apply lightmaps to Bevy meshes; that
will be a followup. It does, however, open the door to future Bevy
plugins that implement baked global illumination.
## Changelog
### Added
The Bevy glTF loader now imports a second UV channel (`TEXCOORD1`,
`UV1`) from meshes if present. This can be used by custom shaders to
implement lightmapping.
# Objective
- Fixes part of #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
# Objective
The objective is to be able to load data from "application-specific"
(see glTF spec 3.7.2.1.) vertex attribute semantics from glTF files into
Bevy meshes.
## Solution
Rather than probe the glTF for the specific attributes supported by
Bevy, this PR changes the loader to iterate through all the attributes
and map them onto `MeshVertexAttribute`s. This mapping includes all the
previously supported attributes, plus it is now possible to add mappings
using the `add_custom_vertex_attribute()` method on `GltfPlugin`.
## Changelog
- Add support for loading custom vertex attributes from glTF files.
- Add the `custom_gltf_vertex_attribute.rs` example to illustrate
loading custom vertex attributes.
## Migration Guide
- If you were instantiating `GltfPlugin` using the unit-like struct
syntax, you must instead use `GltfPlugin::default()` as the type is no
longer unit-like.
