Path: chuka.playstation.co.uk!news
From: James Russell <James_Russell@scee.sony.co.uk>
Newsgroups: scee.yaroze.programming.3d_graphics
Subject: Re: Rotating about an arbitrary axis?
Date: Wed, 23 Sep 1998 10:34:04 +0100
Organization: Sony Computer Entertainment Europe
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Nick Slaven wrote:
> 
> >james, let me know if this works. I (think) I had a problem with the
> >seperate RotMarix functions and never went back to them (had to use the
> >slower RotMatrix() a few times to get the same effect)
> 
> Me too, they seemed to completely distort the tmds (from what I remember) in a
> totally unexpected way, whilst rotmatrix always works.

I'm puzzled by this - I use them all the time with no problems. Probably the thing to remember is
that the matrix you pass to RotMatrixX/Y/Z is both input AND output. It multiplies the input matrix
by the appropriate rotation matrix, it doesn't create one from scratch (whereas RotMatrix does). So
therefore if you want a X followed by Y rotation, you'd go:

MATRIX MyRotation = { { 1, 0, 0 },	// Identity matrix
		      { 0, 1, 0 },
		      { 0, 0, 1 } };
RotMatrixX(firstAngle, &MyRotation);
RotMatrixY(secondAngle, &MyRotation);

and there you go.

Is this what you were doing?

Cheers,

James


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

On the other hand, the early worm gets eaten.