[vtkusers] How to get silhouette/mask of rendered polydata?

[David Gobbi]

Hi Michael,

There is a filter that does this in 3D, it is called 
vtkPolyDataToImageStencil.  There is not yet a VTK filter that does it 
for 2D polydata.

However, if you look at 
VTK/Widgets/Testing/Cxx/TestImageTracerWidget.cxx (look in Hybrid if you 
have VTK 4) there is an example of converting a 2D polydata to a 3D 
polydata with extrusion.  Not quite ideal, but it should work.

 - David


Michael Rice wrote:
> I am rendering a vtkImageData as the background image and a 
> vtkPolyData on top of it. What I need to do is get the elements from 
> the vtkImageData that are beneath the rendered vtkPolyData. Basically 
> I'm trying to use the vtkPolyData to generate a mask for the image.
>
> I thought of using a clip plane on the poly data, but I don't think 
> that will take into account the perspective rendering and the pixel 
> aspect ratio. Is that correct?
>
> Does anyone have any hints or examples on how I can do this?
>
> Thanks.
> Michael
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