Path: chuka.playstation.co.uk!news
From: "Alex Herbert" <alex@herbs.dabsol.co.uk>
Newsgroups: scee.yaroze.freetalk.english
Subject: Re: Have I mentioned this before... bgWorkArea?
Date: Sat, 7 Jul 2001 23:11:45 +0100
Organization: PlayStation Net Yaroze (SCEE)
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Hi Max,

I tried to work this out before and some of it makes sense...  sort of...

If the bg is scrolled to the left a few pixels, an extra tile becomes
visible on the right hand side of the screen making a total of 21 titles
across, hence the first +1 in the formula. The same applies to the y-axis
which explains the second +1.

I'm not sure about the third +1, but it seems to suggest an extra word is
needed per row of tiles.  Can't imagine why - flags maybe?  I first thought
this might be a typo and left it out without any obvious problems, until I
tried a high-res interlaced mode and the bottom 2 rows of tiles were getting
messed up.  I put the +1 back in and it all worked fine.

I'm guessing that the GPU primitive for a 16x16 tile is 6 words in length
and hence the *6.  I'm not sure about the +4.  Flags again, maybe?

I think the *2 is needed for double buffering.  The bgWorkArea will need to
hold 2 packet workspaces as normal - the one being drawn and the one being
prepared.  Not sure about the last +2.

Oh, and the library reference says the unit is 'long', so no idea why floats
would come into it.

Alex


"Max" <mad.max@which.net> wrote in message
news:9i7ktj$dor5@www.netyaroze-europe.com...
> Hmm..
>
> Its really the +1s and +1+1s and *6+4 etc that I don't understand besides
> this usually turns up a float value which is wierd considering the Yaroze
is
> a 32 bit integer machine and the value you get from this formula is always
> FAR bigger that you actually need.
>
> I don't think I'll ever figure this out :(
>
> Max
>
> Alex Herbert <alex@herbs.dabsol.co.uk> wrote in message
> news:9i4sa2$b933@www.netyaroze-europe.com...
> > Hi Max,
> >
> > According to the Library Reference (page 142):
> >
> > size=(((ScreenW/CellW+1)*(ScreenH/CellH+1+1)*6+4)*2+2)
> >
> > Hope this helps.
> >
> > Alex
> >
> >
> >
> > "Max" <mad.max@which.net> wrote in message
> > news:9i4n4l$b931@www.netyaroze-europe.com...
> > > Hey all,
> > >
> > > I've started up again on the 2D tutorial and I'm puzzling over this
> > > bgWorkArea size. Basically I have played around with it quite a bit. I
> > have
> > > 320 [16x16] tiles on the screen (20 tiles width x 16 tiles height) and
> my
> > > bgWorkArea is (20*16)*12 = 3840, now I get the 20*16 bit - the number
of
> > > tiles on the screen but 12 is just an arbitiary number I put in but it
> > won't
> > > work with anything less. I have also tried SCREEN_WIDTH (320) *
> > > SCREEN_HEIGHT (256) = 81920 (the number of pixels on the screen) but
> this
> > > number far outweighs what I actually need as a bare minimum... because
> it
> > > works with 3840.
> > >
> > > Can anyone tell me what the bgWorkArea size is actually mean to be? -
> > > please?
> > >
> > > Max
> > >
> > >
> >
> >
>
>