* Introduce AssetPipeline for performing glTF manipulations.
AssetPipeline offers a place for doing things like scene flattening,
transform baking, and optimization of glTF assets. These types of scene
manipulations will allow us to tackle lightmap baking in the upcoming
atlasgen tool.
This initial PR includes support for scene flattening, which is fairly
non-trivial. Support for parameterization via xatlas will be added in a
subsequent PR.
In a glTF asset, a single mesh can be referenced by several nodes, and
each reference can have a unique transform. AssetPipeline can flatten
the asset such that each instanced mesh has its own vertex data, and the
node transform gets baked into the vertex data.
Recall that gltfio is composed of two libraries: the core library (no
filamat) and the full library. This adds to the size of the full library
but leaves the core library as is.
* Fix various Windows build issues.
2e391b01fe