[vtk-developers] vtkParametricSpline

[Dean Inglis]

Hi,

I've been retrofitting vtkSplineWidget to make use of the
new vtkParametricSpline class.  Two issues arise:

1) in vtkParametricSpline's Initialize member function,
the individual vtkSpline's should call RemoveAllPoints
before adding any points.  I'll check the fix if there are
no objections.

2) vtkParametricSpline parameterizes by length, i.e. Euclidean
distance between points.  This works well for open splines but
not so well for closed splines.  This is because of the left
and right derivative conditions for non-uniformly spaced input
points.  vtkSplineWidget avoids this by parameterising by
sequential point id. Since point ids are all uniformly spaced by 1, 
there is no need to estimate a priori left and right value/derivative 
conditions.  Therefore, I would like to propose an additional boolean ivar
to the class: ParameterizeByLength, and make changes to the
Evaluate and Initialize member functions accordingly.  I'll
wait for comments first though.

BTW, great work on the new Parametric classes!

thanks,
Dean