I thoroughly enjoyed doing OpenGL during my course at university, and recently wanted to dive back into it, so got myself Begining OpenGL Games Programming as it came highly recommended. It has been a very good book, and refreshed my (outdated) knowledge. I have managed to get pretty much all of the code samples to work, converting them from windows to glx (I use FreeBSD/Xorg on an Inspiron 8500 /w GeForce4 4200 Go), and they've all been fine. However, I have just started on working with the Accumulation buffer examples and when the program runs the entire system slows to a crawl. What kills the machine is any calls to glAccum. I'm not sure what is causing it, possibly I'm not creating the window correctly. There's no pixel specification per se, but I am setting GLX_ACCUM_RED_SIZE, GLX_ACCUM_GREEN_SIZE, GLX_ACCUM_BLUE_SIZE, GLX_ACCUM_ALPHA_SIZE in the attributes when setting up. Does anyone have any idea why it might not be functioning properly? Or can point me to some other glx based sample code hat does use the accumulation buffer correctly? thanks