Why so long between draw callbacks for multiple channels?

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Graham Jones (graham.jones++at++sharp.co.uk)
Fri, 07 Feb 1997 18:04:46 +0000

I have an application with 3 channels, each one with a draw callback.
When I look at the stats graph for each channel it looks like each draw
callback is happening about 1/2 a field (8ms or so) after the previous
one finishes.

By the time this has happened twice, between the first and second and
the second and third callbacks, I've lost a tonne of time that could be
keeping my frame rate around 30Hz (or better) instead of 20Hz. Are there
any good explanations for this, or does anybody know how I might reduce
this?

The first two channels are rendering as simple model and the callbacks
only take around 1.3ms each, the third channel is doing much more
complex but only takes 7ms - 10ms. I'm using two processors, the draw
proces on one and the rest on the other. The whole draw process should
only need around 14ms to complete, easily within a 30Hz frame, or even a
60Hz frame, but I only get 20Hz from the system. The app process takes
3ms and cull is only around 1ms and they are happily running in parallel
with draw.

The first two channels are small (320pixels square) and the third is
640x480.

Does this suggest anything? Where should I be looking to regain my lost
time?

Graham.

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England                               Graham.Jones++at++sharp.co.uk
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