Path: chuka.playstation.co.uk!scea!greg_labrec@interactive.sony.com
From: Ed Federmeyer <fedeedw@charlie.cns.iit.edu>
Newsgroups: scea.yaroze.programming.2d_graphics
Subject: Re: More GsBG questions
Date: Thu, 24 Apr 1997 17:28:23 -0500
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Mario Perdue wrote:
> >       Works:                          Gives Black Screen:
> >       Clear OT                        Clear OT
> >       Call GsSort() funcs             Call GsSort() funcs
> >       VSync/SwapBuffer                Call GsSortClear()
> >       Call GsSortClear()              VSync/SwapBuffer
> >       Draw OT                         Draw OT
> 
> GsSortClear() works pretty much like all the other GsSortXxx()
> functions. In the example that works, you do the GsSortClear() AFTER
> you swap the display buffers. In the other example, you do the
> GsSortClear() BEFORE you you swap display buffers. GsSwapDispBuff()
> does a lot more than just changing the pointer to the active display
> buffer. Among other things, it sets the 2D clipping rectangle to
> prevent you from accidently writing to the displayed image. In the
> first example, the GsSortClear() can't do much because the clipping
> rectangle has been moved. In the second, it does exactly what you told
> it to do and clears the screen.

But I guess the thing I don't understand, is that when you say "it does
exactally what you told it to do and clears the screen", I think
it should mean "it puts a command to clear the screen into the OT, so
that later, when you DrawOT(), the first GPU command is 'clear the
current screen'".  In other words, *none* of the Sort() funcs act
immediatly, but just stuff a draw command into the OT.  If that is the
case, it should not matter where the clipping rectangle is when I issue
the SortClear call, but rather, when the rest of the OT is rendered to
the screen, the first thing "rendered" is a big, black rectangle
covering the screen area we are about to draw into.

Maybe if I understood why GsSortClear does not require a priority
like the other Sort() funcs...

EdF

EdF