fast openGL rendering

Feb 5, 2009 at 5:35pm

fast openGL rendering

hi,

i’m trying to do some fast video tracking (>200fps)
so i’ve started to program a GLSL shader for image segmentation
but i realised that i can’t render a very simple OpenGL scene faster than 60 fps ether with jit.window nor jit.pwindow destination
whereas i can do rendering up to 500 fps with a matrix destination
but as i’m using some shader i got the same error as described here :

http://www.cycling74.com/forums/index.php?t=msg&goto=155341&rid=902&S=bab6c5f44f861ffab92ebfb8d6efb474&srch=shader+matrix+render#msg_155341

does anyone know a solution to do openGL readback at high frame rate with shader computing ?

thanks a lot

antoine

#42128
Feb 5, 2009 at 6:04pm

With screen refresh of 60 hertz = 60 cycles/sec = max of 60 fps
(closely equivalent to what your eyes can perceive)

of course you could compute things faster, but to output to screen it
is limited by your refresh rate of you monitor. By default in Jitter,
the GL renderer (render+window) and the refresh rate are synced.

JS

On 5-Feb-09, at 12:35 PM, Antoine Villeret wrote:

>
> hi,
>
> i’m trying to do some fast video tracking (>200fps)
> so i’ve started to program a GLSL shader for image segmentation
> but i realised that i can’t render a very simple OpenGL scene faster
> than 60 fps ether with jit.window nor jit.pwindow destination
> whereas i can do rendering up to 500 fps with a matrix destination
> but as i’m using some shader i got the same error as described here :
> http://www.cycling74.com/forums/index.php?t=msg&goto=155341&rid=902&S=bab6c5f44f861ffab92ebfb8d6efb474&srch=shader+matrix+render#msg_155341
>
> does anyone know a solution to do openGL readback at high frame rate
> with shader computing ?
>
> thanks a lot
>
> antoine

#150595
Feb 5, 2009 at 6:05pm

On Feb 5, 2009, at 9:35 AM, Antoine Villeret wrote:

> but i realised that i can’t render a very simple OpenGL scene faster
> than 60 fps ether with jit.window nor jit.pwindow destination
> whereas i can do rendering up to 500 fps with a matrix destination

I would suggest you disable synchronization on your window (@sync 0).
Otherwise, the maximum framerate is tied to the update of the display.
There will be tearing however, but it sounds like you are using this
less for display than for image analysis.

-Joshua

#150596
Feb 5, 2009 at 6:26pm

thanks for your reply joshua

sync parameter doesn’t affect the frame rate
but i turned off doublebuffer attribute and i achieve 500 fps !!
and you’re right, i’m interested in image analysing not in displaying 500 fps !

thanks

antoine

#150597
Feb 6, 2009 at 3:50pm

>
>
>> but i realised that i can’t render a very simple OpenGL scene
>> faster than 60 fps ether with jit.window nor jit.pwindow destination
>> whereas i can do rendering up to 500 fps with a matrix destination
>
> I would suggest you disable synchronization on your window (@sync
> 0). Otherwise, the maximum framerate is tied to the update of the
> display. There will be tearing however, but it sounds like you are
> using this less for display than for image analysis.
very interesting.
what’s the difference put “sync 0″ on render or/and window ?
thx.


fabrice planquette
elt@altern.org

#150598

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