[vtkusers] Converting a point on a vtkActor to an Image coordinate

[Scott Johnson]

Hello Shaan,

If you have a vtkImageActor it will be returned as a valid pick by vtkPropPicker.  If you look at the actor returned it is probably your image actor. Also, vtkPropPicker won't pick an actor representing a vtkPolyData shape described as line cells, even if it's closed.  In order to get it to pick, the vtkPolyData it must contain closed cells such as polygons.

You can prevent vtkImageActor from being selected by using the PickList functionality in vtkPropPicker.

		-- Scott

-----Original Message-----
From: vtkusers-bounces at vtk.org [mailto:vtkusers-bounces at vtk.org] On Behalf Of Shaan Malik
Sent: Friday, December 02, 2011 9:53 AM
To: vtkusers at vtk.org
Subject: [vtkusers] Converting a point on a vtkActor to an Image coordinate

I've produced an actor from vtkMarchingCubes, which takes a vtkImageData as input.
I want to be able to select the actor in a view and convert the selected point on the actor to the corresponding point on the original image.

In order to get an actor position, I'm using a vtkPicker, but sometimes clicking not on the actor, the picker returns what it thinks is a valid point on the actor. At first I thought this was because the bounding box the Picker uses wasn't a tight fit, but actually the points it returns can fall outside the bounding box of the actor. This makes me assume vtkPicker can't be used to reliably check if a position falls on the actor or not?
The second stage would be to convert the actor position to a position on the original image, but I'm not sure how to go about doing this.

I'm trying to implement a similar feature to what occurs in ITKSNAP, where clicking on a segmentation changes the positions of the orthogonal views.

Hope someone can help,

Thanks,
Shaan


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