Path: chuka.playstation.co.uk!news
From: James Russell <James_Russell@scee.sony.co.uk>
Newsgroups: scee.yaroze.programming.3d_graphics
Subject: Re: Vectors and Matrices Mini Tutorial
Date: Thu, 09 Jul 1998 10:39:44 +0100
Organization: Sony Computer Entertainment Europe
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Message-ID: <35A48FE0.39F7744E@scee.sony.co.uk>
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> Jamin Frederick wrote:
> >
> > But isn't rotation around Z supposed to be (assuming theta goes from X
> > to Y):
> >
> > cos(t)  -sin(t) 0
> > sin(t) cos(t) 0
> > 0        0     1
> >
> > You still have:
> >
> > cos(t)  sin(t) 0
> > -sin(t) cos(t) 0
> > 0        0     1


Another thing I forgot - you might be assuming a different direction of rotation. If multiplied with
the vector on the left, the lower matrix is an anti-clockwise rotation, while the upper matrix is a
clockwise rotation, because:

cos(-t) = cos(t)

and

sin(-t) = -sin(t)

So once again, both are correct - I should have clarified in the tutorial that the matrices I
specified were anti-clockwise.

Cheers,

James
-- 
== James_Russell@scee.sony.co.uk                +44 (171) 447-1626
== Developer Support Engineer - Sony Computer Entertainment Europe

A diagnostic is someone who doesn't know if there are two Gods.