Path: chuka.playstation.co.uk!chuka.playstation.co.uk!chuka.playstation.co.uk!not-for-mail
From: Lewis_Evans@Playstation.sony.com
Newsgroups: scee.yaroze.programming.3d_graphics
Subject: Pivots
Date: 12 Nov 1997 09:37:32 -0000
Organization: Sony Computer Entertainment Europe - 119.SS5
Lines: 45
Sender: news@chuka.playstation.co.uk
Message-ID: <64btcs$qkv1@emeka.playstation.co.uk>
Reply-To: Lewis_Evans@Playstation.sony.com
NNTP-Posting-Host: emeka.playstation.co.uk

From: Lewis_Evans@Playstation.sony.com
To: news@playstation.co.uk




Hi all,
I have a question about the rotations in 3D.
Can the psx handle the pivots for the 3D model's rotations?

-- By pivots, do you mean rotation around internal axes of a model, those
axes being defined
by pairs of vertices? Or the points where models are attached to each
other?

If psx can't handle pivots where is the rotation center for a 3Dmodel?

The simplest way to achieve rotations is around an object's centre.
Every 3d model is displayed by a GsDOB2 structure,
which includes a pointer to a GsCOORDINATE2 structure;
this coordinate system had a matrix member, coord, which expresses
the position and orientation of the object. The position part of that
matrix
(the matrix.t[0-2] fields) describe the position of the polygonal model's
centre
in space.

However, rotations can be achieved about any axis; if you find a decent
3d geometry book, the standard ways of translating points across
coordinate systems and rotating them about any given axis apply
straightforwardly to the matrix structures of the Yaroze.

     Lewis

I'm trying to animate a 3D robot with a hierarchycal system, using
GsLinkObject4,
but I'm not able to rotate the arms near the body.
Help.
Thanks.