[vtk-developers] Re: vtkOBBTree sqrt domain err

[dean.inglis at camris.ca]

David,

what I am doing is segmenting a 2D image of trabecular bone,
shifting the range to [0,1], using vtkContourFilter to pull
out all boundaries at isolevel 0.5.  The isolines are clipped
to a central circular region of interest using vtkSphere and
vtkClipPolyData. The clipped 2D polydata is transformed into 
surfaces using vtkLinearExtrusionFilter to extrude the polylines 
to an out-of-plane height of 1, and then translating the resulting 
polygonal data back -0.5 so that is straddles the image plane.  
I then use vtkOBBTree to generate a search tree so that I can
efficiently run scan lines defined by point pairs in the image plane 
at different orientations (stereology stuff).
How might I check the polydata going into vtkOBBTree: vtkMeshQuality?
Should I make sure that any of the clipped polylines are not reduced
to isolated points (and then extruded as a line)?

Dean


>The ComputeOBB() method on line 270 computes a value called
>"tot_mass" and then divides a bunch of values by it. It looks like
>"tot_mass" is zero if no triangles can be generated from the data
>set, or if the triangles are degenerate.
>
>So apparently vtkOBBTree will crash and burn if it is given data sets
>that cannot be turned into triangles. Dean, do you think that any
>of the data sets that you are giving to OBBTree might not have
>any polygons?