Path: chuka.playstation.co.uk!news
From: James Chow <james@chowfam.demon.co.uk>
Newsgroups: scee.yaroze.beginners
Subject: Re: Questions about VSync.
Date: Tue, 05 May 1998 00:26:32 +0100
Organization: PlayStation Net Yaroze (SCEE)
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References: <354C8851.709D2E83@chowfam.demon.co.uk> <6ij6jd$jpr18@chuka.playstation.co.uk> <354D8AA7.17CA37C6@chowfam.demon.co.uk> <354E298F.2865CC25@netmagic.net>
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Nope. Still confused. Read on.

Elliott Lee wrote:
> 
> And the return values for calling VSync(mode):
> 
>   - if mode>=0:  the number of horizontal sync units should be
>     returned.  If I understand the docs correctly, this should probably
>     be the total number of horizontal lines from the top of the screen
>     to the bottom, including the lines before and after the visible
>     screen data.  This may also include some bogus horizontal retrace
>     period interrupts triggered during the retrace period---the ray
>     gun doesn't always travel in a straight line back to (0,0).
>

Will someone _just_ answer this question then.

while (1) {
  //do work
  cnt = VSync(0);
  //more work
}

Why does cnt _not_ equal 312 for PAL or 262 for NTSC, through
each loop iteration?

>   - if mode<0:  the number of horizontal syncs since the beginning
>     of the program.
> 
> As far as I can tell, the number of h-syncs is probably not a good
> way to time your program because you only get that value after every
> v-sync.  You shouldn't really switch the video pages until the
> vertical retrace begins.  And, getting an arbitrary time is probably
> not that useful because drawing the graphics with the GPU will take
> different amounts of time depending on the complexity of the scene
> you are rendering...
>

I know it's not a good way to do timing, but are there any other
suggestions of how to get a finer resolution than 1/50th sec
or 1/60th sec?  But not too fine, eg. using the root counter, which
flies past like f*** and has probably "gone round" a few
times before you've checked again.

Games like Ridge Racer have timers going down to 1/1000th sec
resolution. Now how to do they manage that?
Personally I find using vsync(-1) + rand()/RAND_MAX
a bit too tacky.

Cheers.
-- 
jc