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View Full Version : render a quad in front of the screen as background, fastest method?



08-26-2005, 08:47 AM
whats the fastest way of rendering a quad that covers the whole viewport, with out rendering nothing i get 2000fps when i render a distant quad i get the same but when i get it close so it covers the whole screen i get 300fps whats the deal?

Aeluned
08-26-2005, 09:28 AM
As you bring it closer and it takes up more of the viewport, you have more pixels to fill. This is the reason for the slowdown.

what board are you using? 300fps is still waaaay more than you need, but it seems a textured fullscreen quad should render faster than that.

08-27-2005, 08:52 AM
an FX5700
yes as i said just 1 quad on fullscreen its taking more than it should i dont get why

in dx i didnt get such a big slowdown

im not clearing the color buffer now as the quad is taking the whole screen thats not needed and i got a nice speed up of about 30fps but still im getting way too low fps for just a quad you get what i mean its just 2 triangles with a 512x512 texture it shouldnt take that much performance!!

Hlz
08-27-2005, 09:36 AM
It's ridiculous to measure/compare performance based on the rendering of a single quad. Performance isn't linear in depth complexity, fill demand, state change and batch overhead. There are real benchmark apps and profilers for this sort of thing. Don't get carried away with blank screen or single quad fps, it's essentially meaningless. Get some real world numbers.

Make sure you know what your render states are. These can have a profound effect on fps, especially at the fringes of nothingness.

08-27-2005, 09:44 AM
oh no no im not measuring anything im just surprised that by rendering a quad i get such a big drop in frame rate and if i render another quad, smaller than that one but in front of the "background" one i get even less fps to a point where i get less than 90 fps and its aweful because they are just a few quads you get waht i mean?

i like opengl i dont like dx thats why im here and im asking the experts

Hlz
08-27-2005, 09:51 AM
Can you post your code?

08-27-2005, 10:43 AM
i dont have it here but im not doing something stupid on the loop trust me i studied many tutorials about opengl and parts of the redbook im not doing something that could eat a lot of processing power on the loop i dont even have depth test enabled (as if i enabled it i lost about 50fps)

no its not using software mode i checked the vendor is nvidia its all in hardware

i have blending disabled which saves me some fps and theres nothing weird on the code its clean

if you want i can make a c++ or pelles c example based on a nehe quad example so you see that theres a big drop on frame rate

08-27-2005, 10:44 AM
i guess c++ would do better no? i dont think that many of you use pelles c

too bad

08-27-2005, 11:15 AM
I get problems like that
I wonder which kind of texture filtering is better for quads that are close to the frustum?.

What would be the fastest for textured quads close to the ortho?