Reimplements "Remove Immutable" by comparing to the skeleton rest.
It is necessary to delay removing animation tracks until after the correct rest pose is calculated in rest-fixer.
Preserves the original implementation in the GLTFDocument / FBXDocument API for compatibility.
This avoids using convex decomposition every time collision is enabled
on a mesh, which can be extremely slow on complex meshes (such as entire
levels).
Rémi Verschelde
Lyuma
Hugo Locurcio
Thaddeus Crews
Muller-Castro
Aaron Franke
BlueCube3310