In My scene I have my main World with a world light and a bunch of world objects, and i have a secondary viewport in which i'm trying to light a single object with a single projection light.
As long as I have the world light enabled no matter what I set my light mask/viewport mask to on my single object it gets lit by the main world light. I would expect that I could use the light mask to disable the world light from the object so i can light it with a separate light source.
At first I thought this was the only problem, but then experimenting with it, I was never able to get the light mask to work on any types of lights or objects. I was able to turn off the projection light from casting on the world objects by using the viewport mask, but it appears that only works for some light sources, not the world light.
Thanks,
Dusty