Ian wrote:Either there is a 1 frame lag between reading values and working out the depth value, or the hardware does a pre depth pass of all the geometry.
I believe that's the second, which would be useful also for transparent polygon sorting. I think it tests for any occluding geometry (which returns los value, with polygon bit noLosReturn unset) in that point. Then skips rendering a particular viewport or node. The fog itself is a viewport attribute and the lens flare is made of transparent textured quads.