Path: chuka.playstation.co.uk!news
From: "Provenzano Stefano" <dragon@azzurra.it>
Newsgroups: scee.yaroze.programming.3d_graphics
Subject: Re: Pivots
Date: Thu, 13 Nov 1997 15:08:34 +0100
Organization: PlayStation Net Yaroze (SCEE)
Lines: 54
Message-ID: <64f1do$4vi169@chuka.playstation.co.uk>
References: <64btcs$qkv1@emeka.playstation.co.uk>
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Lewis_Evans@Playstation.sony.com ha scritto nel messaggio
<64btcs$qkv1@emeka.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?
I mean the rotation center of the model. The point where I apply the
rotation on the model. Is this a fix point or I can place it on the model
where I would?

>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.
Then  if I want to rotate a model in a corner and not in the center the only
way is rotate the object on the center of the object and then translate it.
Is it true?
Because if I want to rotate a leg of my robot and make only a rotation of
the model by the center at the end the leg isn't in a good position and then
I must move it. Is this the only way to work ?

>     Lewis
Thanks for the replay.

>
>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.
>