Path: chuka.playstation.co.uk!scea!peter_alau@playstation.sony.com
From: jamin1@psu.edu (Jamin Frederick)
Newsgroups: scee.yaroze.programming.2d_graphics
Subject: Re: Scrolling backgrounds
Date: Wed, 08 Jul 1998 22:46:36 GMT
Organization: SCEA News Server
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On Wed, 08 Jul 1998 11:21:54 +0100, James Russell
<James_Russell@scee.sony.co.uk> wrote:

>Mark Green wrote:
>> 
>> Unfortunately this seems to be very inefficient (requiring two full-screen
>> blits per frame, one to scroll the buffer and another to copy it to the frame
>> buffer) and will not work with the non-blocking operations anyway since the
>> scroll must be assured complete before the copy can take place.
>
>I guess you're calculating the next line in main ram and loading it with LoadImage,
>then performing a MoveImage to scroll it?
>
At the start, wouldn't this be a slow way to do it -- getting a line
from main RAM (load to video), and then moveimage before anything even
happens?  I thought main -> video blitting should not generally be
done during gameplay, too slow?


>You can call these two functions together - since GPU commands are queued up internally,
>the MoveImage will wait until the LoadImage has finished before completion. So you
>don't have to go:
>
So which and how many GPU commands can you call before you MUST call
DrawSync(0)?

>LoadImage(myNewLine);
>DrawSync(0);
>MoveImage(scrollMove);
>

>just:
>
>LoadImage(myNewLine);
>MoveImage(scrollMove);
>
Similarly, is making many more moveimages than necessary going to slow
down performance, than if just block blitting were done instead?  It
seems like doing a line-by-line thing might clog things up, especially
if loading all the time from main mem.


Jamin

>This might speed your program up a bit (but won't affect the GPU speed).
>
>-- 
>== James_Russell@scee.sony.co.uk                +44 (171) 447-1626
>== Developer Support Engineer - Sony Computer Entertainment Europe
>
>(((((This tagline in Stereo where available)))))