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Display list overhead - TomorrowPlusX - Dec 20, 2004 11:14 AM


Sometime ago I asked about wether or not it would be faster to draw meshes as a compiled display list or as a VBO.

OSC replied that display lists would be faster by and large, but that there was some sort of per-use penalty.

Anyway, I've been sharking to try to clean up some hotspots and am debating wether I should have the shadow volumes of static ( e.g. immobile geometry ) continue to be cached in a display list or wether I should just draw it in immediate mode.

I'll post results, but at the moment I'm curious if anybody has suggestions, or experience to share.

Display list overhead - skyhawk - Dec 20, 2004 11:29 AM

everything that has static geometry that isn't a part of my HUD/menu, I use display list

Display list overhead - TomorrowPlusX - Dec 20, 2004 12:14 PM

After a quick stab during my lunch break, I've noticed that going from display lists to immediate mode has perked things up noticeably. I'm maxxing at 44fps now, when it was 30 earlier.

Of course, I'm caching the shadow volume geometry -- so it's not being recalculated -- but instead of drawing it via display list I'm just cranking out the cached vertices in immediate mode.

Display list overhead - skyhawk - Dec 20, 2004 12:54 PM

how small are these things?

Display list overhead - TomorrowPlusX - Dec 20, 2004 02:13 PM

That's a good point. My current quasi-stress-test scenario is a ton ( well, about 250 ) of meshes with about 60 or so triangles apiece. The meshes themselves are drawn via display lists, but it's shadow drawing that's taking up something like 30 percent CPU time. Oddly, it's not the volume projection, but the drawing of the volume that's the big hit ( according to shark ).

Well, I guess that makes sense since the drawing is when the geometry is uploaded.

I'm thinking now that there's probably a threshold point over which display lists become useful, and under which they cost too much. I guess the trick is finding that point...