Path: chuka.playstation.co.uk!news
From: Developer Support <dev_support@interactive.sony.com>
Newsgroups: scee.yaroze.beginners
Subject: Re: Stuck with Sprites - Oddness`
Date: Tue, 05 Aug 1997 08:22:37 +0100
Organization: PlayStation Net Yaroze (SCEE)
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Mark Green wrote:
> 
> Ok, after spending a while with this machine, I've finally gone from a
> completely blank screen to a completely blank screen with a slight tinge
> of red...  Basically, I understand (I think!) how the graphics system
> works, but it seems to have inconsistencies in it that I don't
> understand.  Perhaps some kind soul could explain a few things..
> 
>   1 - Ok, I have the frame buffer, which is basically a massive
> scratchpad except that part of it at any given moment will be onscreen.
> Things like GetTPage and LoadImage, etc. seem to refer to coordinates in
> this.  However, when it comes to actually _drawing_ things, it seems
> that the system compensates for the location of the current drawing
> buffer in the scratchpad.  (Evidence: The CHECK program, when it
> recalculates the positions of the sprites, does not have an amount that
> it adds on in order to draw in the second frame buffer on every other
> frame).  Is this true?  What if I really do want to draw in the texture
> space, CLUT, or similar?

The GPU draws on screen ( The 512 by 1024 VRAM ) using a structure
called a DRAWENV to tell it where the origin is, and what size to use
for screen clipping. The graphics initialisation normally sets up two of
these structures for the double buffering, but you can use others if you
want to draw off screen ( For reflection effects etc )

> 
>   2 - What colour does FntPrint() text come out in?  (I was trying to
> FntPrint() some text in the scratchpad, mark that area as TextureSpace
> then pick it up in a sprite, but it never shows up...)
> 

You can change the colour of FntPrint using either ~crgb where rgb are
single digits from 0-9 ( you can go above but it's in ASCII order, not
hex )

>   3 - Once you've drawn an Ot, you can do whatever you like to the Ot in
> memory, right?

Once the drawing has finished the Ot is dead.. but don't modify it
before drawing has finished.

> 
>   4 - You don't actually *need* two sets of GpuPackets for two buffered
> frames if you're only drawing one at a time (which is a stupid thing to
> do, but is simple, so that's what I'm trying to do at the moment :) )
> 

If you drawsync after drawing ( So that the CPU waits for the drawing to
complete ) You will only need one set of Gpupackets+OT, however you will
lose a lot of performance that way.

>   5 - The drawing commands draw on the buffer that is *not* visible at
> the moment, right?
> 

Yup...(Unless you tell them not to)

>   Thanks for any help!!
> Mg


Cheers,

Colin.