Turns out glTF doesn't actually put metalness into R and roughness into
G, even though the naming suggests that. This was done originally, but
then they changed that in order to be compatible with UE4 and allow for
a more efficient storage of an occlusion map.
Because this feels extremely arbitrary, the docs have added rationale
for each of the packing variants, and I'm also renaming the packed
attribute and checks to imply the red channel isn't used.
This is a bit huge because of all the new overloads that take a
MaterialLayer instead of a string, but all that is just boring
boilerplate. Additionally this:
* exposes glTF clear coat parameters (which, interestingly enough,
reuse existing attributes and don't introduce any new)
* provides a convenience wrapper in PbrClearCoatMaterialData
* and a convenience base for material layer wrappers that redirect
all APIs with implicit layer argument to desired layer instead of the
base material
Well, "basic". Practically mirrors glTF PBR materials:
- builtin metallic/roughness
- the KHR_materials_pbrSpecularGlossiness extension
- extra normal/occlusion/emission maps
- exposes the implicit metallic/roughness and specular/glossiness
packing, but also allows separate maps with arbitrary packings as
well as two-channel normal maps (instead of three-channel)
- provides convenience checks for the most common packing schemes
including MSFT_packing_normalRoughnessMetallic and the three variants
of MSFT_packing_occlusionRoughnessMetallic
- teaches PhongMaterialData to recognize packed specular/glossiness
maps as well
Next up is exposing at least one layer extension, and then I'm done
here.
With API analogous to the (relatively) new AnimationData -- with one
buffer containing all index data and one buffer containing all vertex
data, both meant to be uploaded as-is to the GPU.
This will eventually replace MeshData2D and MeshData3D, backwards
compatibility and wiring up to other APIs will be done in follow-up
commits.
Vladimír Vondruš