[vtkusers] Re: Clarification: vtkImageReslice->reorienting a volume

[Audrius Stundzia]

Hi David,

Thanks for the explanations. Much appreciated.

One (last ?) pedantic question. If I set the origin of the vtkImageData such 
that the rotation / origin is about a particular point in my data set, then 
are the actual (x, y, z) values of the rotataion / origin point preserved if

1. if the SetOutputOrigin is set, but not SetOutputExtent
2. if the SetOutputExtent is set, but not SetOutputOrigin
3. if both SetOutputOrigin and SetOutputExtent are set
4. if both SetOutputOrigin and SetOutputExtent are not set

Best regards,

Audrius

> > >If you just want to change the orientation, just use
> > >SetResliceMatrix but not SetResliceTransform.
> > >
> >
> > Got it. Thanks.
> >
> > >The 3x3 portion of the matrix should contain the direction cosines.
> >
> > Got this too. However, a clarification of the man pages entry for
> > void SetResliceAxes (vtkMatrix4x4 *)
> > would be very helpful:
> > o The standard (i,j) = (row,column) convention is being used?
>
>Yes, as per vtkMatrix4x4.
>
> > o The column vectors are those of the old axes? or the new axes?
>
>The column vectors are the old axes.  The SetResliceTransform method
>works in the same way, it is a transformation from the new coordinate
>space to the old coordinate space.  The interpolation algorithm naturally
>works in that direction.
>
> > Ie., x_p = Rx where R is the rotation matrix, are the column vectors the
> > axes associated with x or with x_p? Looking at Eqn (3-13) in the book, I
> > think column vectors are the "new, target" axes associated with x_p.
> > Correct?
>
>Other way around.  But you should really try some simple test cases to
>ensure that you're doing it the right way.
>
> > Finally, I think vtkImageReslice is a most useful contribution to vtk.
>
>Thanks.  It was my first VTK class, and I kind of let it grow out of
>control.  It still doesn't do anti-aliasing though...
>
>  - David
>
>
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