# Incorporating a 3x3 rotation matrix into a vtkTransform

Ron Inbar ron at eun.co.il
Tue Jan 18 07:16:49 EST 2000

```Tim,

If you really want to understand homogenous coordinates, consult a textbook
on Projective Geometry.  It's more than a calculation trick.

Regards,

Ron

----- Original Message -----
From: Tim Hutton <T.Hutton at eastman.ucl.ac.uk>
To: <S.N.Holt at rl.ac.uk>; <vtkusers at gsao.med.ge.com>
Sent: éåí ùðé 17 éðåàø 2000 18:56
Subject: RE: Incorporating a 3x3 rotation matrix into a vtkTransform

> No, the point sets are in 3d but thanks for your reply. I've been reliably
> informed the solution is
>
> T = a b c 0
>     d e f 0
>     g h i 0
>     0 0 0 1
>
> Cheers,
>
> Tim. (wishes he could understand homogeneous coordinates...)
>
> At 16:48 17/01/00 -0000, you wrote:
> >I've assumed your dealing with 2D (its 3x3), so the matrix should be:
> >
> >T = a b 0 c
> >    d e 0 f
> >    0 0 1 0
> >    g h 0 i
> >
> >
> >Steve.
> >
> >> -----Original Message-----
> >> From: Tim Hutton [mailto:T.Hutton at eastman.ucl.ac.uk]
> >> Sent: Monday, January 17, 2000 4:09 PM
> >> To: vtkusers at gsao.med.ge.com
> >> Subject: Incorporating a 3x3 rotation matrix into a vtkTransform
> >>
> >>
> >> vtk users,
> >>
> >> Simple question, I'm a bit rusty with my 4x4 transformation
> >> matrices. I
> >> have a routine that computes the  rotation required to LS
> >> align two sets of
> >> points. It returns a 3x3 rotation matrix, how do I add this to a
> >> vtkTransform. Is it as simple as adding a row of 1's?
> >>
> >> ie.
> >>
> >> R = a b c
> >>     d e f
> >>     g h i
> >>
> >> T = a b c 0
> >>     d e f 0
> >>     g h i 0
> >>     1 1 1 1
> >>
> >> Or is it more complicated?
> >>
> >> Cheers,
> >>
> >> Tim.
> >> --------------------------------------------------------------
> >> -------------
> >> Tim Hutton, Research Assistant            Email:
> >> T.Hutton at eastman.ucl.ac.uk
> >> MINORI Project
> >> http://www.eastman.ucl.ac.uk/~dmi/MINORI
> >> Dental and Medical
> >> Informatics                   Tel: [+44] (0171) 915 2344
> >> Eastman Dental Institute, UCL                    Fax: [+44]
> >> (0171) 915 2303
> >> 256 Gray's Inn Road, London WC1X 8LD, UK
> >> --------------------------------------------------------------
> >
> >
>
>---------------------------------------------------------------------------
--
> >This is the private VTK discussion list.  Please keep messages on-topic.
> >Check the FAQ at: <http://www.automatrix.com/cgi-bin/vtkfaq>
> >To UNSUBSCRIBE, send message body containing "unsubscribe vtkusers" to
> ><majordomo at gsao.med.ge.com>.  For help, send message body containing
> >"info vtkusers" to the same address.     Live long and prosper.
>
>---------------------------------------------------------------------------
--
> >
> >
> >
>
>
> --------------------------------------------------------------------------
---
> This is the private VTK discussion list.  Please keep messages on-topic.
> Check the FAQ at: <http://www.automatrix.com/cgi-bin/vtkfaq>
> To UNSUBSCRIBE, send message body containing "unsubscribe vtkusers" to
> <majordomo at gsao.med.ge.com>.  For help, send message body containing
> "info vtkusers" to the same address.     Live long and prosper.
> --------------------------------------------------------------------------
---
>
>

-----------------------------------------------------------------------------
This is the private VTK discussion list.  Please keep messages on-topic.
Check the FAQ at: <http://www.automatrix.com/cgi-bin/vtkfaq>
To UNSUBSCRIBE, send message body containing "unsubscribe vtkusers" to
<majordomo at gsao.med.ge.com>.  For help, send message body containing
"info vtkusers" to the same address.     Live long and prosper.
-----------------------------------------------------------------------------

```