[SDL] Windowed OpenGL Performance on OS X

Richard Schreyer rws_list at girr.org
Thu Nov 6 10:29:01 PST 2003

Well, this fixed itself with a restart.  I'm now getting ~70fps in 
windowed mode.

Interestingly enough, in Panther compositing on OpenGL surfaces is 
indeed done even on machines without QE, unlike in 10.2  (recall, my 
card is a rage128 pro, 8mb).  Having a transparent terminal on top of 
the testgl example dropped framerates from 70fps back down to ~5, right 
where it was before.  (Compositing still isn't done at all for DVD 
player surfaces, only for OpenGL).

There are two possibilities:
1) There was a completely transparent fullscreen window on top of it, 
and Quartz was compositing.  What app created/owned this, I don't know.
2) Some resources on the card were not freed when a previous process 

Richard Schreyer

On Nov 5, 2003, at 4:21 PM, Darrell Walisser wrote:

>> or even worse, rendering, copying to main memory, compositing via 
>> Quartz, then
>> copying back the framebuffer, which is completley unnecessary.  It 
>> should just
>> be rendering to a surface in the video card and ignoring all 
>> compositing (as it
>> should on a machine without QE).
> That's right. OpenGL bypasses the Quartz compositor unless other 
> windows overlap the OpenGL window. So windowed mode should run near 
> fullscreen mode (though fullscreen mode can pageflip on some cards and 
> it as more video memory at its disposal so it tends to be faster).
>> One other idea is that with the recent 10.3 upgrade, Apple is now 
>> doing
>> compositing in software even on non-QE enabled systems.  I'll 
>> probably test this
>> by putting together a GLUT example tonight and seeing how it 
>> performs, or by
>> placing something transparent on top of the SDL window and seeing if 
>> it
>> composites correctly (it shouldn't).
> It could be that you don't have enough video memory available so it's 
> reverting to a software surface. Apple recommends 32MB VRAM for QE, so 
> try disabling QE if you've got that enabled and also lowering the 
> desktop/window size/depth.
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