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From: Lewis_Evans@Playstation.sony.com
Newsgroups: scea.yaroze.programming.3d_graphics
Subject: Hi-res mode seems to studder
Date: 23 Jan 1998 10:12:37 -0000
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From: Lewis_Evans@Playstation.sony.com
To: news@playstation.co.uk


To:       Lewis Evans
cc:
From:     news @ playstation.co.uk
Subject:  Hi-res mode seems to studder:scea.yaroze.programming.3d_graphics




From: "Kevin Davis" <KMFSV@aol.com>
Newsgroups:
scea.yaroze.programming.3d_graphics,scee.yaroze.programming.3d_graphics
Subject: Hi-res mode seems to studder
Xref: chuka.playstation.co.uk scea.yaroze.programming.3d_graphics:190
scee.yaroze.programming.3d_graphics:444
My program is using 640x480 resolution, however I sometimes have bad
problems with the screen studdering.  It almost looks like I'm not
switching double buffers but I'm using GsGetActiveBuff() each time to
switch between the buffers.  I initialize the graphics like this:
        GsInitGraph(640 ,480, GsOFSGPU|GsINTER, 1, 0);  // screen 640x480
When I switch to low-res mode (320x240) I haven't encountered this problem
yet.  Has anyone else overcome this problem?
Kevin



Your call to GsInitGraph is correct; it's also true that there is only
_one_ buffer in VRAM,
ie one area which is 640x480, the GPU handles the switching of odd/even
lines each frame
to effect double buffering. After your call to GsInitGraph, are you doing
this:

GsDefDispBuff(0,0,0,0);       // different to the call under
low-vertical-res programs


There is another major reason why your program may shudder.
Under vertical hi-res, which 640x480 definitely is, the double-buffer
mechanism is dependent
on VSync; the only way to avoid heavy flicker is to force the program to
run at maximum frame rate
(6o fps NTSC, 50 fps PAL). Hence, under hi-res interlace, the main loop
used is often this:

hsyncCount = VSync(0);
ResetGraph(1);      // if drawing hasn't finished yet, forget it, since we
must keep up the frame rate

rather than under a typical low-res main loop which says

DrawSync(0);        // make sure all drawing completes, we can afford to
drop frames
hsyncCount = VSync(0);        // now wait for v-blnk


Ie: under interlace, your program must run at max frame rate (50 or 60) or
flicker is inevitable.
If doing this involves too much drawing to be missed out on, you may be
better off in low-res.

The main reason lots of games are not done in hi-res is because of this
necessity
of maximum frame rate; basically, you can't draw as many things.

     Lewis