Path: chuka.playstation.co.uk!news
From: "Rikki Prince" <netyaroze@rprince.dircon.co.uk>
Newsgroups: scee.yaroze.beginners
Subject: Order in main display loop
Date: Sat, 18 Sep 1999 15:41:35 +0100
Organization: PlayStation Net Yaroze (SCEE)
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I've been playing about with some wrapper functions to simplify writing
games, for example sprite initialisation function (which everyone has made
or copied out of G. Bain's tutorials :), and so on. When I did a simple
version of some of these most basic wrappers, I had two functions for the
main loop, basically setting up the graphics(GsGetActiveBuff() etc), and
then waiting for DrawSync etc. These were used as first and last functions
called in my main while(RUNNING) loop, with pad handling and
rendering/sorting of primitives, so the loop looked like:

while(RUNNING)
{
        GraphicsLoopStart();    /* The variables used were global */
        PadHandler();
        DisplayScreen();
        GraphicsLoopEnd();
}

In this code GraphicsLoopStart() basically consisted of:

        ActiveBuff = GsGetActiveBuff();
        GsSetWorkBase(&GpuPacketArea[ActiveBuff]);
        GsClearOt(0, 0, &OrderingTable[ActiveBuff]);

and Graphics LoopEnd() was:

        DrawSync(0);
        VSync(0);
        GsSwapDispBuff();
        GsSortClear(0, 0, 255, &OrderingTable[ActiveBuff]);
        GsDrawOt(&OrderingTable[ActiveBuff]);

Now when I've come to tidy these functions up, with the variables used (OT,
active buffer etc) being passed as arguments, I tried to integrate these
into one function, so that it could be called at the end or the start of the
loop. I thought this would be possible, as in the loop example above, I
thought it could be rearranged as:

while(RUNNING)
{
        GraphicsLoopEnd();
        GraphicsLoopStart();    /* The variables used were global */
        PadHandler();
        DisplayScreen();
}

or

while(RUNNING)
{
        PadHandler();
        DisplayScreen();
        GraphicsLoopEnd();
        GraphicsLoopStart();    /* The variables used were global */
}

However, when I came to test this, it didn't work at all. After messing
around with it, using the actual code in place of a function call, and then
splitting the code into the two separate functions, and putting them in
different places in relation to the other function calls in the loop, I
found it only worked when the 'GraphicsLoopStart' code was at the start of
the loop, and the 'GraphicsLoopEnd' code was at the end. I think the idea of
combining the two parts should work, at least the do in theory, but I can't
seem to get it to work - I get a warped image of the 'start-up brick
screen', followed by a GPU timeout message in siocons, then the blue
background screen I should be getting, and control of the program (well
Start + Select to exit).

Has anyone got any ideas on why it isn't working? I suppose it could be my
whole testing program etc, as it's a bit recycled from old stuff, but it
works with the code at the start and end, but not all at the end, or al at
the start. Can someone tell me if it shouldn't work in theory, and that I've
got completely the wrong idea? I'd be grateful for any help whatsoever.

Thanks
Rikki