MacOSX accumulation buffer.

Hello,

Maybe my question is not really related to the HOpenGL library in  
particular, but more general a MacOSX+OpenGL problem. I hope some of  
you guys recognize this issue.

It seems there is no way to get the accumulation buffer to work  
efficiently on MacOSX. Using this buffer to implement a neat motion  
blur slows down the framerate to less than 8 fps on my machine. A  
brand new Macbook with the newest NVIDIA GeForce 9400M running a very  
simple demo with just one 3D torus.

I am using this initialization code:

 > initialDisplayMode $= [
 >     ...
 >   , WithAccumBuffer
 >   ]
 >
 > initialDisplayCapabilities $= [
 >     ...
 >   , Where DisplayAccA IsEqualTo 8 -- Also tried 1, 16, 24, 32...
 >   ]

And use the buffer like this:

 > withMotionBlur comp = do
 >   accum Mult 0.95
 >   comp
 >   accum Accum 0.05
 >   accum Return 1.2

The result looks verry pretty but is terribly slow.

Is there someone how has ever used the accumulation buffer on MacOSX  
without experiencing slowdowns?

Thanks,

--
sebastiaan