[vtkusers] vtkImageData::FindCell

[David Doria]

> No, that's not what tolerances are for.  The tolerance is only used in
> cases where, due to expected roundoff error, the algorithm is uncertain
> about whether the point is inside or outside.  If the algorithm is certain
> about whether the point is inside or outside, the tolerance is not applied.
> Keep all tolerances on the scale of the anticipated roundoff error, i.e.
> between 1e-16 and 1e-3 depending on the algorithm.  If you aren't sure
> what the expected error is, use the default tolerance.
>   David

So it considers a point on the boundary to be "outside" no matter the
tolerance? Doesn't that seem silly? Often you may know the coordinates
of the grid points and want to get the cell id they are associated
with. This method should work for all such points, but it seems to
work only on points that aren't on the boundary faces of the
structured grid?

David