[vtkusers] Coincident polydata render

[Mathieu Moigner]

Dear vtk users,

Here is my problem :

This is what i want : http://www.hostingpics.net/viewer.php?id=353989591.png
And what i get : http://www.hostingpics.net/viewer.php?id=764980532.png

The cube is a vtkpolydata, I create others vtkpolydata (coincident with 
the top surface of the cube), so it is not surprising to get this result.


But if I create the polydata using vtkExtractSelection on the cube, and 
then adding the result to the scene, I get this : 
http://www.hostingpics.net/viewer.php?id=136487353.png, the render is ok.

I have absolutely no idea why.

I hope I made myself clear and someone could give me a hint.

Thks in advance.