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

[Shaan Malik]

Hi Scott,

Sorry, to clarify, my pipeline is as follows:

vtkImageData->vtkMarchingCubes->vtkPolyDataMapper->vtkActor->vtkRenderer->vtkRenderWindow

I have a vtkActor which I'm trying to pick, not a vtkImageActor.

What I'm trying to do is, once a point on the vtkActor is picked, figure 
out which point in the original vtkImageData it corresponds to.

Thanks for the reply,
Shaan

On 02/12/11 16:17, Scott Johnson wrote:
> 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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