[vtkusers] vtkWedge confusion

Jeff Lee jeff at cdnorthamerica.com
Thu Feb 9 07:26:25 EST 2006


Hi,
I am confused about the vtkWedge celltype -  in the manual, and current 
documentation, the node ordering is such that the bottom tri points away 
from the top tri (using the right-hand rule).  Previous code 
documentation suggests that the bottom tri points into the top tri (like 
a hex).  I did a test where I placed a tet next to a wedge(using the 
current definition of node ordering) in a vtkUnstructuredGrid, and cut a 
plane section through both cells.  The resulting contour pieces had 
normals facing in opposite directions (the wedge pieces were pointing 
opposite to the tet pieces).  When I make the base of the wedge point 
into the top tri, all the contour pieces point in the same direction.  
Based on my assumption that the contouring algorithm is designed to make 
the orientation of all output tris consistent , is it correct to 
conclude that the vtkWedge cell type is documented incorrectly, and that 
the current picture in the manuals should have nodes 1 and 2 swapped as 
well as 4 and 5 swapped?
Regards,
Jeff



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