Yes, as you said the problem is fillrate. The GPU can only draw X pixels per second. If you're drawing even a few particles that fill a large part of the screen, your card will be able to draw less frames per second. This is a common issue.

You could try using a single fullscreen quad to simulate being close to a cloud, or in one.

Hope this helps.

Quote:Original post by aero68
Why gets pointsprite so slow when a couple of them fills a large part of the screen ? I have alot of them and render them very fast but when I get close
my FPS drops alot! The number of sprites doesn't seem to make a big differet,
it more like a fillrate problem.

Your graphics card, no matter how powerful it is, can only fill so many times the whole screen per second. If you've got an overdraw of 100 or more then you're dead no matter what you do. It's particularly bad if you use blending because in addition the card has to waste bandwidth to do all those read/modify/write to memory.

Try to reduce the number of sprites, see if you can achieve the same effect with much less particles. Also if you come close you can make them more and more transparent until they disappear (so that they never take the whole screen). You can also try to emulate some volumetric effect in a pixel shader rather than waste so much fillrate/bandwidth by drawing over and over.

LeGreg