This PR adds support for Mixamo FBX imports (via backend conversion to
glTF/glB) and some miscellaneous improvements to the animation systems.
### User-facing improvements
* Retargeting math has been fixed to eliminate jittering issues
* Retargeter can now handle animated bone translations when present
(generally this is only used for root motion)
### Housekeeping / Code improvements
* Animation-related components and system logic have been moved to a
dedicated `anim` module and `AnimPlugin`
* Retargeting stuff has been moved from the `bvh` module to
`anim::retargeting`
* Component-based solution for marking an entity as an animation
retargeting source makes it easy to extend the retargeting functionality
to new types of source animations
### Limitations
Currently the code assumes that there will be at most one animation
source at a time. That single animation (if present) will be retargeted
to all other skeletons in the scene. A component-based solution for
directing a specific target skeleton to use a specific source animation
is possible, but will require some additional consideration around the
implementation design for the read-only "viewer" modes.
### Test animations:
* Hip-Hop Dancing (Mixamo): ?mode=viewer&mixamo=mocap/hip-hop-dancing.gltf
* Shuffle (MocapNET): ?mode=viewer&bvh=mocap/shuffle.bvh
* Scott (MocapNET): ?mode=viewer&bvh=mocap/scott.bvh
* Scott 1 (MocapNET): ?mode=viewer&bvh=mocap/scott1.bvh
This PR adds support for BVH animation files, with a custom animation
player and retargeting solution for our Blender Rigify-based skeletal
meshes.
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Co-authored-by: Brooks Palin <brookspalin710@gmail.com>
Danny McGee