Path: chuka.playstation.co.uk!news From: Christoph Luerig Newsgroups: scee.yaroze.programming.3d_graphics Subject: Re: Bezier and Matrix Date: Mon, 05 Oct 1998 09:46:18 +0200 Organization: PlayStation Net Yaroze (SCEE) Lines: 86 Message-ID: <3618794A.7FA8C48@immd9.informatik.uni-erlangen.de> References: <01bdee25$048270e0$77e16dc0@ulthar.han.de> NNTP-Posting-Host: faui90.informatik.uni-erlangen.de Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="------------B6B269A4195270C2E3DC1A51" X-Mailer: Mozilla 4.04C-SGI [en] (X11; I; IRIX 6.3 IP32) --------------B6B269A4195270C2E3DC1A51 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Roland Boettcher wrote: > Something for the math gurus... > > I'm working on a bezier spline based track editor > (thanks go to Lars for his source). > > For the bezier coordinates I have the rotation matrix, > but for the points in between I can only calculate the > coordinates. How do I calculate the rotation matrix > for those points? > > Please have a look at my first draft. Then you'll see > what I mean. > > http://www.netyaroze-europe.com/~roland/ftp/bezier.zip > > Roland Hi Roland! I am not sure, if I got you right. But one main property of Bezier patches (as for their bigger brothers the NURBS) is affine invariance. This means, it does not matter, whether you perform subdivision on your controle grid and then apply the affine transformation, or you apply the affine transformation to the controle grid and do the subdivision afterwards. Christoph -- ------------------------------------------------------------------- Christoph L"urig cpluerig@immd9.informatik.uni-erlangen.de Graphische Datenverarbeitung Tel.: +49 9131 8529929 Universitaet Erlangen Fax: +49 9131 8529931 cpluerig@immd9.informatik.uni-erlangen.de --------------B6B269A4195270C2E3DC1A51 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit Roland Boettcher wrote:
Something for the math gurus...

I'm working on a bezier spline based track editor
(thanks go to Lars for his source).

For the bezier coordinates I have the rotation matrix,
but for the points in between I can only calculate the
coordinates. How do I calculate the rotation matrix
for those points?

Please have a look at my first draft. Then you'll see
what I mean.

http://www.netyaroze-europe.com/~roland/ftp/bezier.zip

Roland

 Hi Roland!
I am not sure, if I got you right. But one main property of Bezier patches (as for their bigger brothers the NURBS) is affine invariance. This means,
it does not matter, whether you perform subdivision on your controle grid and then apply the affine transformation, or you apply the affine transformation to the controle grid and do the subdivision afterwards.

Christoph 

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Christoph L"urig          cpluerig@immd9.informatik.uni-erlangen.de
Graphische Datenverarbeitung                  Tel.: +49 9131 8529929
Universitaet Erlangen                         Fax:  +49 9131 8529931

cpluerig@immd9.informatik.uni-erlangen.de
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