Texture Channel Packing

So I've intentionally kept this description a bit more broad, since there is discussion going on here

In the unreal documentation they outline their format as:
R = Metallic
G = Roughness
B = Ambient Occlusion

And in another UE article it’s:
R = Ambient Occlusion
G = Metallic
B = Roughness

Whereas ours is:
G = Roughness
B = Metallic

See: https://github.com/jMonkeyEngine/jmonkeyengine/blob/d57c362ec3b510c1ba6356f719efa3b1576b95c6/jme3-core/src/main/resources/Common/MatDefs/Light/PBRLighting.j3md#L30

GLTF Spec also uses "our" format and yet that leads to problems when trying to export a GLTF Project from blender instead of hand crafting Textures to our format. See https://hub.jmonkeyengine.org/t/environment-cam-and-light-probe-question/41241

Under Texture Requirements they also pack Ambient Occlusion into the R channel, which we don't do yet, opinions?

Maybe the GLTF Exporter is broken or our importer is broken? It definitely looks like Roughness and Metallicness is swapped somewhere for users importing from blender.

I didn't want this issue to end like this, I was expecting the GLTF Spec to say something different (namely the Unreal Definition 1), we should still keep track of this in an issue. I'll report back if I find more information

Start with jme3-core/src/main/resources/Common/MatDefs/Light/PBRLighting.j3md at the referenced channel definitions, then review the linked GLTF and Blender discussions. Determine whether the exporter or importer swaps metallic and roughness channels and whether ambient occlusion should be included. Done requires an agreed format and verified channel mapping.