glxgear and glxinfo confusion

[Alan Cox]

On Mon, 23 Jan 2012 11:58:31 -0800
Joe Zeff <joe at zeff.us> wrote:

> On 01/23/2012 11:42 AM, Marko Vojinovic wrote:
> > I always found the output of glxgears quite confusing, to say the least. If
> > you think logically --- your screen displays a picture 60 times in one second,
> > and some graphics cards (like Intel) render the frames in the same rythm, to
> > display the images of the gears animation 60 times per second.
> 
> Motion Pictures are shown at 32 fps and nobody complains about 

32 ?? less than that.

> flickering, but there are people who claim that anything less than 70 
> fps on their monitor flickers. 

They are not comparable.

One is a scanning line display the other is a continuous output beam.
There are two big reasons that matters

1.	The display behaviour is quite different, on a CRT all but one
scan line of pixels is fading to black, on a film this isn't the case

2.	Because it is scanning you have two frequencies - the update
frequency and the animation frequency. You therefore get beat frequencies
and images changing mid scan - aka "tearing".

And if you want to know about the difference and whether it matters there
is an astronomical amount of proper scientific peer reviewed literature
on the subject.

Alan