Path: chuka.playstation.co.uk!news
From: Harvey Cotton <hc054@mdx.ac.uk>
Newsgroups: scee.yaroze.programming.3d_graphics
Subject: Re: Looking for...
Date: Thu, 07 Jan 1999 11:42:26 +0000
Organization: PlayStation Net Yaroze (SCEE)
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References: <368a4f74.24103378@news.playstation.co.uk> <368CA5F0.6EB6@mdx.ac.uk> <3691A8DA.E2D92BBC@znet.com>
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> > > And could someone give me a functioning 3d Sprite Routine, or post it
> > > here? Yes, I saw the old messages, but I would like to get it in one
> > > piece, that would be more than nice....8-D
> 
> > Heres a function to draw a 3d sprite:
> >
> 
> thanks.  I'm curious about--
> 
> >                 sprite.scalex=sprite.scaley=16777216/transformedPosition.vz;
> 
> Where does the 16777216  value come from?  I use
> sprite.scalex=sprite.scaley=ONE*projectionDistance/transformedPosition.vz;
> where ONE=4096 (from libps.h)

The value is a scaling constant. There is no perfect value because it
all depends
on how big you've drawn your sprite. It your sprites are tiny, you may
wish to
use much larger constants.
 
> GsSortSprite(&sprite,&OTable_Header[CurrentBuffer],transformedPosition.vz>>(precision-2));
> 
> What is "precision" (I assume it's the number of bits of the ot size?)
> and why do you subtract 2?
> Mine works, I it's just that I found the right value by trial and error.

I think is +2 but I cannot remember. Its something to do with the way
polygons are
inserted into the ordering table (sprites work differently). It was
mentioned early
on this newsgroup.
-- 
Regards  |  E-mail: hc054@mdx.ac.uk
Harvey   |  ICQ: 4269478