Much appreciated. The reason for the Bevy 0.15 delays has mostly been due to me procrastinating on this work. I'll get around to reviewing it as soon as I can!

Locally, I tried to do a MaterialExtension from StandardMaterial, but out.color = apply_pbr_lighting(pbr_input); doesn't really work (this is what gives us the really dark output, independent of the light direction/color/intensity). Maybe someone more knowledgeable about these shader dark arts can take a look at the bevy_pbr code.

I'm not too worried about how 3D looks. Even when I first implemented it, it's not correct. Spine isn't meant to work in a PBR environment. It's possible with enough voodoo and I didn't want this library to be the limiting factor, but it's not a priority.

There's a few things that need to get sorted out in 2D examples. The custom_material example should not have all these black boxes:

And even the simple example seems to have some alpha problems:

How it should look:

It's probably something simple, just gotta track it down.