If you want to limit this texture to a specific object, or group of objects in my case, then you need to do something in the node graph to specify which objects you want it to render. Here is a render of a window, I wanted an ID for just the tapes, which were flat planes with an alpha cutting them out:
If I drop the tapes alpha texture into the ‘Extra Texture’ slot and render it will come out like this:
We don’t want everything to have the texture so we do this:
So open the node editor, select your Extra Texture element and graph it, then I middle mouse dragged my group of objects from the outliner into the graph also. Then you simply take the ‘message’ output from the group node and plug it into ‘vray_exclude_list_extratex’. Then back in the Attribute editor for the Extra Texture, make sure ‘Exclude list as inclusive set’ is ticked.
And thats it, you should have something settings that looks like this:
And this is what the render should now look like (but your version):
This is handy for tons of stuff, enjoy!