[vtk-developers] vtkOBBTree vtkPoints vs vtkPolyData on the input

[Burlen Loring]

Hi all,

I am having some strange results when using the vtkOBBTree. I am using 
only the method ComputeOBB. I had been passing polydata through however 
had recently switched to passing through only the points, as sometimes 
the polydata was too large to fit in the memory of a single compute 
node.  I have noticed that when I call ComputeOBB with a vtkPoints I get 
a drastically different OBB than when I call it with a vtkPolyData. For 
example http://quaoar.sr.unh.edu/obb/bigObb.png the white surface is the 
OBB that results from passing the points of the red dataset through the 
OBB filter. When I use the polydata I get an OBB that tightly fits the 
input data set. I expect in both cases (vtkPoints/vtkPolyData) to get a 
tightly fitting OBB since the input is an axis aligned box itself. Is 
this expected behavior? Why would the results differ so drastically?

Thanks in advance
Burlen

-- 
Burlen Loring
Kitware, Inc.
R&D Engineer
28 Corporate Drive
Clifton Park, NY 12065-8662
Phone: 518-371-3971 x137