Hi, I myself am working on a 3D engine, and I learned a lot from the NeHe site (thanx for that). But what I still need to know, and have been looking for for ages, is how do you determine when to draw a corona (lightflash as in unreal) Currently, I just use the Z-buffer, but that doesn''t give the desired result, since the rule for drawing corona''s is when the center is visible, the whole thing should be visible. My engine is a Portal/Octree/Hardware Z-Buffer based engine

Right, ofcourse.
So obvious and yet...
thanx a lot m8