I've been working with the pbr shaders recently and I've hit a snag. Typically when creating a material, there are many different gloss values. A standard specular pipeline would include a way to modulate gloss with a texture like with the spec map. A logical solution would be to put a gloss map in the alpha channel of the spec map, but it looks like that's unsupported. Is there a way to use a gloss map with a specular type pbr shader?