[xlib] howto create screenshots?
tom at dbservice.com
Mon Sep 12 18:30:19 PDT 2005
Tomas Carnecky wrote:
> I've seen that when my application runs as the only opengl application
> on the system, I could get 20-30 fps, but as soon as I've started
> another opengl app (cedega/wine World of Warcraft or even glxgears at
> 300x300px), the framerate dropped down to 2-8 fps.
I've just done some tests and this came out:
with just glReadPixels into a 'GL_PIXEL_PACK_BUFFER_EXT', I can easily
get ~500MiB/s which makes ~100fps.
If I add a memcpy(), to copy the image pixels into a (static) local
buffer, the framerate drops down to ~60fps (300MiB/s).
if I start glxgears, the framerate drops down to 6-8 fps (30-40MiB/s),
depending on how large the glxgears window is (300x300 up to fullscreen).
When I move the windows around (and both opengl apps are running) I can
feel lags of about 0.5 sec, but the mouse stays always responsive as
usual. If only the capture app is running, There are no lags.
I can post the source code of the application I've used to make these
tests if anyone wants.
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