Path: chuka.playstation.co.uk!news
From: Chris Chadwick <xjk18@dial.pipex.com>
Newsgroups: scee.yaroze.programming.2d_graphics
Subject: Re: Yaroze - was I right to buy ?
Date: Thu, 24 Apr 1997 03:45:02 -0700
Organization: PlayStation Net Yaroze (SCEE)
Lines: 48
Message-ID: <335F39AE.16E8@dial.pipex.com>
References: <01bc5030$6f732280$2f19e8c3@cma>
NNTP-Posting-Host: aj043.du.pipex.com
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
X-Mailer: Mozilla 2.02 (Win95; I; 16bit)

Chris Allmark wrote:
> 
> When a *large* texture (like 3 x 2 texture pages) which contains sprite
> animation "frames" and I want to access (for instance) the bottom right
> frame do I need to use GetTPage against the texture page co-ordinates of
> the original graphic, or the texture page that the frame falls within ?

I haven't tried this out but I'm fairly sure you have to use the coords
of the Tpage that the frame falls within because the u,v members (sprite
pattern in-page offset) of a GsSPRITE object are 'unsigned chars' and
therefore can only specify a 255 pixel offset (max).
 
> Am I right in thinking that I can only map textures to sprites which are
> held within VRAM ?

Yes (no one prove me wrong, please! :-) thats what the texture pages are for
specifically - as far as I can gather, the GPU doesn't have direct access to
the main memory - the drawing primitives stored there are passed to the GPU
by the DMA controller. 

> This can't possibly be the case for commercial
> applications - are the graphics "cached" or background loaded directly from
> CD directly when required ?

I don't know whether the full dev kit librarys have direct CD to frame buffer
functionality (Sony?) but I would guess that they don't and that commercial
games fall under the same restriction, in that respect. Having said that, the
PSX can stream FMV off CD into the frame buffer, but this probably goes through
the CD-ROM buffer memory first...

> If I am limited to using graphics that can be
> held within VRAM space then how the hell can I do anything other than small
> test programs ?

You must be developing a game with a huge amount of sprites/frames per sprite/
very large sprites! :-) I find the 1MB (minus double buffers) can hold quite a
sizable amount of sprites (especially if 4/8bit), and you could always shift
textures in and out of RAM/VRAM *quickly* using LoadImage/MoveImage/StoreImage.
(Sorry if I'm blathering on - it's just my oppinion...)
 
> ...and if that's the case then the Yaroze is a real waste of time and
> money.

Don't give up (Yet! :-) It's early days for all of us!

Keep on truckin'

Chris