Say I have a closed-off room that it s not possible to get into. The only space linking this room to the map's playable space is a brush-based, func_detail window with frame that completely seals its hole; the player will never see the other side of this window or its frame. At the moment, I add nodraw to the back of the window frame but leave the back of the window itself as the same glass texture as on the front, in order for light inside the room to be cast outside. Would it be possible, though texture flags, to create a tools texture that acts in exactly the same way as nodraw (ie it isn't rendered) but does not cast shadows? In this case I would be able to apply it to the back of my window, have the window not render its back face but still have light cast through it.