vtkSpline

Section: Visualization Toolkit Filtering Classes

Usage

vtkSpline interpolates a set of data points (i.e., interpolation means that the spline passes through the points). vtkSpline is an abstract class: its subclasses vtkCardinalSpline and vtkKochenekSpline do the interpolation. Note that this spline maps the 1D parametric coordinate t into a single value x. Thus if you want to use the spline to interpolate points (i.e. x[3]), you have to create three splines for each of the x-y-z coordinates. Fortunately, the vtkParametricSpline class does this for you.

Typically a spline is used by adding a sequence of parametric coordinate / data (t,x) values followed by use of an evaluation function (e.g., vtkCardinalSpline::Evaluate()). Since these splines are 1D, a point in this context is an independent / dependent variable pair.

Splines can also be set up to be closed or open. Closed splines continue from the last point to the first point with continuous function and derivative values. (You don't need to duplicate the first point to close the spline, just set ClosedOn.)

This implementation of splines does not use a normalized parametric coordinate. If the spline is open, then the parameter space is (tMin <= t <= tMax) where tMin and tMax are the minimum and maximum parametric values seen when performing AddPoint(). If the spline is closed, then the parameter space is (tMin <= t <= (tMax+1)) where tMin and tMax are the minimum and maximum parametric values seen when performing AddPoint(). Note, however, that this behavior can be changed by explicitly setting the ParametricRange(tMin,tMax). If set, the parameter space remains (tMin <= t <= tMax), except that additions of data with parametric values outside this range are clamped within this range.

To create an instance of class vtkSpline, simply invoke its constructor as follows

  obj = vtkSpline

Methods

The class vtkSpline has several methods that can be used. They are listed below. Note that the documentation is translated automatically from the VTK sources, and may not be completely intelligible. When in doubt, consult the VTK website. In the methods listed below, obj is an instance of the vtkSpline class.