Path: chuka.playstation.co.uk!news
From: Mark Henkelis <mark.henkelis@virgin.net>
Newsgroups: scee.yaroze.programming.3d_graphics
Subject: Re: GsInitGraph 640x512
Date: Thu, 29 May 1997 00:26:56 +0100
Organization: PlayStation Net Yaroze (SCEE)
Lines: 39
Message-ID: <338CBF40.5AB8@virgin.net>
References: <336730D1.12A8@interactive.sony.com>
NNTP-Posting-Host: p43-grouse-gui.tch.virgin.net
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
X-Mailer: Mozilla 2.02E-VN005  (Win95; I)

laura smith wrote:
> 
> Some of you may have noticed the chrome demo doesn't clear the screen.
> The reason for this is a bug in the libraries when using GsInitGraph
> with 640x512, the demo will work with 640x480, and an update using only
> this will be posted soon.
> 
> As for the bug, Colin is working on a fix.
> 
> Stuart

If only I'd read this sooner! Spent a happy few hours trying to work out 
why my demo didn't clear the screen first. In the end I just amended 
GsDRAWENV as follows:

void InitialiseAll (void)
{
   // graphical initialisation:
   SetVideoMode(MODE_PAL);
   ResetGraph(0);
   GsInitGraph(SCREEN_WIDTH, SCREEN_HEIGHT, GsOFSGPU, 1, 0);
   ClearInterlacedScreen();
   GsDefDispBuff(0, 0, 0, 0);
   GsInit3D();
...
}

void ClearInterlacedScreen (void)
{
   // HACK TO CLEAR SCREEN IN PAL 640x512 INTERLACED MODE
   GsDRAWENV.isbg = 1;
   GsDRAWENV.r0 = 0;
   GsDRAWENV.g0 = 0;
   GsDRAWENV.b0 = 0;
}

This works fine for me and also in the old chrome demo.

Mark.