Re: [Dri-devel] glxgears oddity.

[Dave J. <da...@su...>]

On Thu, May 01, 2003 at 02:31:47PM -0600, Brian Paul wrote:

 > This is (loosely speaking) an optical illusion.  The drawing rate is much 
 > faster than the refresh rate of your monitor.  Basically, your monitor is 
 > "sampling" the frame buffer at a frequency much lower than the frequency at 
 > which the drawing is taking place.  Because of this, you're seeing the gears 
 > at basically random rotations.
 > Ever seen a wagon wheel apparently spin backward at the movies or on TV?  It's 
 > sort of like that.

Sure, it's s similar effect.
 
 > The LIBGL_THROTTLE_REFRESH env var can limit drawing rate to the monitor 
 > refresh rate to fix this (but then you'll only get 70-85 fps or so).
Yep, that does indeed make things silky smooth again.
Making glxgears fullscreen (or even partially covering it with an xterm)
also makes the 'problem' go away. Freaky.

        Dave

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| Dave Jones.        http://www.codemonkey.org.uk
| SuSE Labs