Commenting here to say, the export to VMT feature is up and running.

Originally posted by xdshot:

Can it approximately convert Principled BSDF to Source VertexLit?

The point isn't to convert from Principled to VLG, it's to replace it. It won't convert PBR textures to a phong workflow. There's no simple algorythmic way to do that. It's meant only as a compatibility layer between blender's engines and the source engine, not Principled

Originally posted by Artfunkel:

That's very cool! I probably wouldn't ship that with the tools directly as they don't deal with shaders or textures, but I would happily add a link to your addon to the website when it's read to ship.

Alright Thanks!

this might help

I'm currently building a tool for facilitating VMT creation in the blender workflow. I call it BlenderVertexLitGeneric (BVLG) because what it does is implement a VertexLitGeneric-like shader in blender allowing for quasi-native compatibility.

I think this could be cool thing to add to BST but of course I'm not demanding or even expecting anything.
if you want to check it out I've created a page for it on the dev site
At this point it's good enough that I feel comfortable putting it out there but it definitely needs some more work.

The long term goal would be to make it into an addon that could directly bake to VMT and combine VTF alphas so content creators don't have to worry about it. Idealy make it a higher level of abstraction to make it look cleaner