[vtkusers] Default coordinate system for vtkPolyData !

[M.Salman at surrey.ac.uk]

Once again thanks for your reply Amy.Perhaps you could help me a bit more.I am trying to represent the coordinates of  vertices in my vtp model in terms of  "rotation invariant" basis so that the new coordinate values don't change when a model is rotated. 

I pick up three point A,B and C using the point Ids of the model and use them to define this "rotation invariant "basis S. 
vector X= vector AB cross vector AC
vector Y= vector X cross vector AB

now AB, X and Y define new orthogonal basis. These basis should be rotation invariant because the basis undergo the same rotation as any of the points does.If coordinates(world coordinates presumably)of all the vertices in the model are described in terms to these basis vectors and then the model is rotated,these new transformed coordinates must not change.But when I do it practically, they do change.

Is there anything wrong with the logic ?

I am really stuck with this. 

Best Regards,
- Salman
-----Original Message-----
From: Amy Squillacote [mailto:ahs at cfdrc.com]
Sent: Tue 15/01/2008 2:36 PM
To: Salman M Mr (PG/R - Electronic Eng)
Cc: vtkusers at vtk.org
Subject: Re: [vtkusers] Default coordinate system for vtkPolyData !
 
Hi Salman,

vtkPolyData does not have a notion of what coordinate system it's in. I 
don't think there's a way to get this information from a .vtp file. The 
vtkActor is coordinate-system aware. Typically you use the world 
coordinate system when you're setting up the points for a vtkPolyData, 
but this does not have to be the case.

- Amy

M.Salman at surrey.ac.uk wrote:
>
>
> Thanks for your reply Amy.Supppose I have a vtp model,how do I find 
> out which coordinate system is it using?
>
> I really appreciate your help,
>
> Thanks
>
> Salman
>
>
> -----Original Message-----
> From: Amy Squillacote [mailto:ahs at cfdrc.com]
> Sent: Tue 15/01/2008 2:06 PM
> To: Salman M Mr (PG/R - Electronic Eng)
> Cc: vtkusers at vtk.org
> Subject: Re: [vtkusers] Default coordinate system for vtkPolyData !
>
> Hi Salman,
>
> When saving out a .vtp file, VTK uses whatever point coordinates
> (vtkPoints) are defined in the vtkPolyData being written out.
>
> - Amy
>
> M.Salman at surrey.ac.uk wrote:
> >
> >
> > Hi All,
> >
> >
> >
> > I want to know which default coordinate system from the following does
> > VTK use while saveing a model in vtp format.
> >
> > DISPLAY -             x-y pixel values in window
> >   NORMALIZED DISPLAY -  x-y (0,1) normalized values
> >   VIEWPORT -            x-y pixel values in viewport
> >   NORMALIZED VIEWPORT - x-y (0,1) normalized value in viewport
> >   VIEW -                x-y-z (-1,1) values in camera coordinates. (z
> > is depth)
> >   WORLD -               x-y-z global coordinate values
> >   USERDEFINED -         x-y-z in User defined space
> >
> >
> > this is really important for me .
> >
> > Best Regards,
> >
> > Salman
> >
> >
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