Path: chuka.playstation.co.uk!scea!greg_labrec@interactive.sony.com
From: mperdue@hrtc.net (Mario Perdue)
Newsgroups: scea.yaroze.programming.2d_graphics
Subject: Re: Sprite/OT trouble
Date: Sun, 03 Aug 1997 04:41:25 GMT
Organization: SCEA Net Yaroze News
Lines: 74
Message-ID: <33e4094a.25115732@205.149.189.29>
References: <01bc9f6f$da300e60$37f135ce@jjustice.iquest.net>
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John,

I don't see anything wrong with what you've posted here. Any chance we
could see the rest of the program?

Mario

On 2 Aug 1997 19:10:52 GMT, "John Emmer" <jjustice@cs.bsu.edu> wrote:

>Here's my main display loop:
>
>while(!(padValue&PAD1_SELECT))
>{
>	padValue = PadRead();
>
>	activeBuff = GsGetActiveBuff();
>		
>	GsSetWorkBase((PACKET*)GpuPacketArea[activeBuff]);
>		
>	GsClearOt(0,0,&WorldOT[activeBuff]);
>		
>	// register sprites in OT (just players for now)
>	for (i = 0; i < 2; i++)
>	{
>		GsSortSprite(&(player[i].tank.turret.turretSprite),
>			&WorldOT[activeBuff],0);
>		GsSortSprite(&(player[i].tank.tankSprite),
>			&WorldOT[activeBuff],1);
>	}
>
>	// add a dummy tank because last sprite is not displaying
>	GsSortSprite(&(computer[0].tank.tankSprite),&WorldOT[activeBuff],0);
>		
>	DrawSync(0);
>
>	VSync(0);
>
>	GsSwapDispBuff();
>
>	GsSortClear(255,255,255,&WorldOT[activeBuff]);
>
>	GsDrawOt(&WorldOT[activeBuff]);
>}
>
>And here are my questions:
>
>	A couple of weird things are happening.  I want the turrets to display
>over the tanks, so I set the priority of the tanks to 1 and the turrets to
>0.  (My OT length is currently 4). For some reason, if I swap the order of
>the two lines inside the for loop, the screen gets garbage.  In their
>current order it works.  I know "Doctor, it hurts when I put them in this
>order" "If it hurts, don't do it!" - but I want to understand _why_ this
>makes a difference.
>	Secondly, as you see from the comment after the for loop, the fourth
>sprite doesn't display (actually, it flickers on for a fraction of a second
>every now and then).  I figured it had something to do with the timing, so
>I added a fifth sprite that I don't currently care about, so that the fifth
>one wouldn't display instead of the fourth one that I do want.  But why
>isn't the fourth sprite displaying?
>	Finally, both of these problems go away if I run the program stepwise
>through the CodeWarrior Debugger.  This suggests to me even more strongly
>that the problem has to do with timing.  But I have my DrawSync(0) and
>VSync(0) in there, and the rest of my code looks like the examples I've
>seen (thanks Shadow and Mario!) as far as I can tell.  What's up?
>	Thanks!
>
>-- 
>  John Emmer     Video Game Enthusiast, Philosopher, Fledgling Programmer
>     jjustice@cs.bsu.edu  jjustice@iquest.net  jpemmer@bsuvc.bsu.edu  
> 
>    Vectrex; 7800, Supercharger, Lynx, Jaguar; NES, SNES, Virtual Boy;
>  Turbo Duo & Express; SG, SGCD, 32X, Saturn; 3DO; PlayStation, Yaroze;
>C64, A600, A1200, P100; Arcade Centipede, Spy Hunter, Neo-Geo; BA, MA, ABD