[vtkusers] Get an X-Ray Contour from a 3d object

[Justus Kreuels]

Hello.

I search a filter, which creates a 2d curve from a 3d object. The 3d 
object is for example a bone. The resulting curve should be the contour 
of this bone I see, when I look on it in a specified direction, similar 
to the shape of a bone of on a X-Ray Image.
I tried to program something like this, but this is not easy because 
the curve has a third dimension. So i cannot use a cutter or something 
like this.

With which filter I can get such a curve. 

Thanks and Best Regards
Justus