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Acheum
04-13-2003, 11:52 PM
In my program, I want to use the accumulation buffer. It's the first time I use it, so I first tested it with the code :
glAccum(GL_ACCUM,1.0);
glAccum(GL_RETURN,1.0);
and display the result.
The display is OK when I comment these two lines, but when I use them, all is stretched, as if all lines displayed were the same as the center line. What does this mean ?
Thanks for tour answers.

Bob
04-14-2003, 01:49 AM
Make sure you request a pixel format that has an accumulation buffer. Could be that you don't have one.

Acheum
04-14-2003, 02:52 AM
I tried tu use glGet, with argument GL_ACCUM_ALPHA_BITS, GL_ACCUM_RED_BITS...
All calls return a value of 16, so it seems that the pixel format has an accumulation buffer.

Acheum
04-15-2003, 10:14 PM
Nobody has an answer to my question ?
Please...

marcus256
04-16-2003, 09:42 PM
...nobody uses the accumulation buffer since it's almost never hardware accelerated http://www.opengl.org/discussion_boards/ubb/frown.gif (which is a shame IMO)

I believe it's implemented by reading back an on-card buffer to system memory, and then operated on in software, and finally written back to the gfx card. (=rendering done in hardware, but accum buffer ops in software => slow!) [correct me if I'm wrong]

Acheum
04-16-2003, 11:54 PM
It's ok, it was finally a problem of drivers. I put the last ATI drivers and all is correctly displayed, without changing a line in my program.