The first image (vsyncOFF-1GPU.jpg) shows the timing rendering 1 slave camera on an extended (2880x900) dual-monitor on a single Nvidia card. Note the 211Hz rendering rate with VSync off and the substantial Draw/GPU overlap. [Note that in all of these timing tests none of the CPUs appeared more than 50% loaded.] This is the type of performance I was anticipating.
Now all I did was turn on Vsync. The second image (vsyncON-app-long.jpg) now shows a 60Hz rendering rate as expected (with a delay after GPU waiting for VSync), but no Draw/GPU overlap, there's even a slight gap between the two? Why is this different now? I suspect this issue is caused by the graphics card having an upper limit on the number of buffer swaps queued up. Once the limit of queued swaps is reached, the card won't start processing the next frame until it performs the swap for the current frame, thus causing the "gap" that you see. This is, of course, not an issue with vsync disabled. Not sure about the "gap" in the rest of your post; perhaps Robert has more info. I hope that helps, Paul Martz Skew Matrix Software LLC http://www.skew-matrix.com <http://www.skew-matrix.com/> +1 303 859 9466
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