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View Full Version : display lists slowing down no-zbuffer rendering?



Jernej
02-03-2004, 09:47 AM
this is exactly what appears to be happening
to me: if i use pre-made display lists for
particle system in my game i get around 78 fps
but, after messing up something i began
generating particle sprite geometry on runtime

and what is the vierd thing that happened now
is that fps averaged to 80-81 fps o_0

it might be just bad nvidia opengl icd
windows implementation ?

i'm not realy sure about it - why do
generated display lists work slower than if
i generate those 2 triangles at usage?

what could lead to this behavour?

dorbie
02-03-2004, 10:04 AM
Display lists help for relatively large pieces of geometry (what large is changes depending on the platform). There is an overhead to calling them that must be amortized by the improvement is performance for what they draw. In addition display lists should be generated once and called many times. So, a particle system is one area where display lists are absolutely useless, or worse.

Particle systems in a display list might require matrix manipulation to position the particles unless you're using a fancy vertex program, that would be a huge overhead compared to the correct way of doing things; simply manipulating the vertex values using the CPU or GPU.

So.... try using VAR of some other fast way of dispatching to the graphics card from system memory instead of display lists, but it depends on how you're updating the particles.

rgpc
02-03-2004, 06:13 PM
Lets not forget to ask how big the display lists are. ie. How many verts/triangles etc.

dorbie
02-03-2004, 09:56 PM
It's a particle system... with 2 triangles per particle, read the post. 'nuff said.

rgpc
02-04-2004, 04:09 AM
Of course. Der http://www.opengl.org/discussion_boards/ubb/redface.gif

That's what happens when you get distracted...