[vtkusers] VtkVolumePicker choosing the edges of my volume

[Doug Hoppes]

Thanks for the response.  

That was the function that I was using.  However, how do you determine the isovalue of the surface without creating an isosurface?

Essentially what I would need is the list of the pixels that would be along the line of the camera position and where I picked on the screen.

Doug

-----Original Message-----
From: David Gobbi [mailto:david.gobbi at gmail.com] 
Sent: Thursday, March 14, 2013 2:36 PM
To: Doug Hoppes
Cc: vtkusers at vtk.org
Subject: Re: [vtkusers] VtkVolumePicker choosing the edges of my volume

The picker has a method called SetVolumeOpacityIsovalue() that allows you to select an isovalue for picking.  As the documentation states:

  "If you want to do the pick based on an actual data isovalue rather than
   the opacity, then pass the data value through the scalar opacity function
   before using this method."

So if you know the isovalue, then use the volume's opacity transfer function to find the corresponding opacity.  Then call SetVolumeOpacityIsovalue().

 - David

On Thu, Mar 14, 2013 at 11:25 AM, Doug Hoppes <dhoppes at mbfbioscience.com> wrote:
> Hi all,
>
>
>
>                 Okay, not sure what is going on here.  I have an image 
> stack that is pretty dark with a semi-white blob in the center.  I 
> would like to be able to select any point on that blob.
>
>
>
>                 I find that I can do this, if I turn the pickable 
> setting of the volume off, and create an isosurface for the semi-white 
> blob.  However, ideally, I would prefer to just use the 
> vtkVolumePicker to select the blob, rather than having to spend the time creating the isosurface.
>
>
>
>                 When I try to click on the white area of the blob, I 
> always get the edges of the volume.  Is there a way to ignore the 
> volume's dark areas?  Since I don't know what the exact pixel values 
> are, is there a way to define a range of pixels to ignore (i.e. ignore 
> all pixels < 10 and pixels > 100)?
>
>
>
> Doug