[vtkusers] vtkImplicitSelectionLoop and vtkImplicitBoolean problem

[Katherine Kerekes]

Thanks David, you are right--I wasn't using the correct class to do what I
wanted.  I wanted to have a loop intersecting one slice of my data.  

It seems that the most effective way I have found to do this is to use
vtkExtractVOI to extract the one slice that I want from my volume and then
use vtkClipDataSet to clip using a vtkImplicitFunction (my loop).  

Now my problem is that I have drawn an irregular shape (my loop), but when I
clip the dataset and visualize the result, the clipping region seems to be a
rectangle drawn around my loop instead of only the points inside my loop.
Can anyone explain how to get just the points inside my loop?

Thanks,
Kate Kerekes

-----Original Message-----
From: David.Pont at ForestResearch.co.nz
[mailto:David.Pont at ForestResearch.co.nz] 
Sent: Monday, May 23, 2005 5:15 PM
To: Katherine Kerekes
Cc: 'VTK Group'; vtkusers-bounces+david.pont=forestresearch.co.nz at vtk.org
Subject: Re: [vtkusers] vtkImplicitSelectionLoop and vtkImplicitBoolean
problem

"Katherine Kerekes" <kerekes at fastmail.fm> wrote on 24/05/2005 01:20:55:

> I am trying to clip a block of data (using vtkClipper inside out
> on).  I am using a vtkImplicitBoolean function that consists of a
> vtkPlane and a vtkImplicitSelectionLoop where the plane origin is
> one of the points in the vtkImplicitSelectionLoop and the plane
> normal is the same normal as the loop normal.  I set the
> OperationType to Intersection.  So I thought that the intersection
> should be one slice of the loop.  But when I visualize this clipper
> shows the selection loop running through the entire dataset (not
> just one slice of the loop).  Any ideas what I am doing wrong?
>
> Thanks,
> Kate Kerekes_______________________________________________
> This is the private VTK discussion list.
> Please keep messages on-topic. Check the FAQ at: http://www.vtk.
> org/Wiki/VTK_FAQ
> Follow this link to subscribe/unsubscribe:
> http://www.vtk.org/mailman/listinfo/vtkusers

Katherine,
   it sounds like the clipper is doing exactly what it should do, the loop
is infinite in length, you can use a plane to cap one end then it is still
infinite in length in the other direction. I suppose if you used another
plane you could cap the other end to define a region, which you could think
of as a 'slice' of finite thickness.
If you really want a slice (zero thickness) you should use vtkCutter.
  regards, Dave P