[vtk-developers] Implicit functions - Ability to specify if it is evaluable

[David Gobbi]

Hi Karthik,

Is there any reason why you cannot just extrapolate your polyplane
out to infinity?  I'm concerned about making a change to the implicit
functions that requires a modification to vtkCutter, since vtkCutter
is far from the only class to use them.

 - David


On Mon, Feb 14, 2011 at 10:04 AM, Karthik Krishnan
<karthik.krishnan at kitware.com> wrote:
> Hello:
>
> I need to cut a dataset with a polyplane. So I wrote a vtkPolyPlane class
> that derives from vtkImplicitFunction; so one could use it in combination
> with a vtkCutter.
>
> It does not quite work, unless the polyplane is infinite in extent. What I
> need is a way for the implicit function to specify that it cannot be defined
> at a certain point. The hack I have now is for the Evaluate method to return
> VTK_DOUBLE_MAX and a modification to vtkCutter to avoid contouring any cells
> which contain a point where the evaluated function value is VTK_DOUBLE_MAX.
>
> I propose
> - Adding a IsDefined method to vtkImplicitFunction that returns true by
> default (subclasses may override it)
> - Modifying vtkCutter to query IsDefined() on points in a cell before
> attempting to contour a cell.
>
> Any thoughts.
>
> Thanks
> --
> karthik
>
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