I want to make an RTS that will use BSP maps where units can go up/down stairs and underground. I have an idea for 3d fog of war that would show only what is within the player's units' line of sight. Each unit would be treated as a point source of light and a depth map created from its point of view.
How many units could I support if I did a pass for each unit? How would I do the multipass? Redraw to texture each time and pass in the texture from previous pass and choose the brighter pixels of the two?