Path: chuka.playstation.co.uk!news
From: sceetech <ps_yaroze@interactive.sony.com>
Newsgroups: scee.yaroze.programming.3d_graphics
Subject: Re: New gte functions
Date: Mon, 07 Apr 1997 11:59:24 +0100
Organization: SCEE
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Alex Amsel wrote:
> 
> Is there any chance of having a few gte functions provided in the near
> future? At the moment I can't see a way of doing a custom 3d engine
> other than doing things like perspective, subdivision and lighting in
> software. I can't even see any specific rotation functions so we have
> no access to the internal rotation matrix.
> 
> Am I wrong? If so, call 0800 666 666
> 
> My knowledge is a bit limited here, so if any commercial developers
> out there can help the rest of us...
> 
> * Alex Amsel * Into Beyond Web Design & JAVA Programming *
> * http://www.intobeyond.com  *  WWFC Play off ****ers'97 *
> MM: "Hand the opposition the lead, the supporters love it"

I'm not very clear what you're asking for;
there are already lots of GTE functions provided, and together
with the Gs calls provided give plenty of foundation
for any 3d engines
eg.

Perspective transformation: look at the demos
scei/bmirror
scee/flying and scee/tunnel and scee/modules/ninth
for the tranformation of coordinates from world coords
onto the screen with perspective transformation.

Subdivision: each GsDOBJ2 polygon-model-handler
has an attribute flag; five levels of automatic subdivision
cab be set using the 9th, 10th and 11th bits of this flag.
See the documentation for details; words of warning
concern the speed penalties for subdivision, and 
the fact that massive amounts of it are liable
to crash everything.

Lighting: Gs provided several means of lighting
(a) back colour, the OT default colour
(b) ambient lighting
(c) fogging: distance and colour variables
(d) three parallel light sources of any colour
these are all easy to use and described in the documentation

Specific rotation functions:
the demos solar, solar2, dungeon and flying
show different ways to rotate an object, or a matrix,
or a coordinate system (related point: see the functions
for perspective transformation mentioned above).
In those demos are straightforward ways of rotating
a matrix (hence, object or coord. system) in the two main
interesting ways: firstly around world axes, secondly
around matrix's own axes. When these two (especially the
latter) are sorted, almost everything becomes clear;
when a matrix is updated only by translations and by
rotating about its own axes, it has two vital properties:
the rows express its axes as vectors in the world coordinate
system, the columns express the world's axes as vectors
in the matrix's coordinate system.


Hope this is of use


	Lewis