Support for Gloss maps

[chicken-suop]

First off, I'm not very experienced with Unity, so if there's might be an easy solution I'm missing.

I'd like to add support for a Gloss map, or what Unity calls a Metallic/Specular map. I want this so I can define parts of my model as glossy/shiny and parts duller. Think, an knight wearing shiny armour and dull cloth pants.

I'll give it a shot myself, and if I figure it out, I'll submit a PR. Would like some help though

[ecker00]

Should be quite straightforward to make this, add an extra texture input which is multiplied with the output of the "Gloss" in the sub graph. Here is an example: