I'm trying to get an overlay on the player's vision using an env_screenoverlay. The trouble is that when i call StartOverlays I get this error: "** CViewRender::PerformScreenOverlay: Screen overlay wants to render, but it's been disabled!"

Incidentally, the env_player_viewfinder would serve my purpose as well but I'm reading that it's for coop and doesn't seem to want to work in my single player map

Really? What overlay are you using? Mine just died silently.

I've tried a few of the materials in the materials/effects/ directory. The first time i try to activate the env_screenoverlay it gives the error, but then doesn't give it again until I re-launch the game (so even after reloading the map the error doesn't show up again)