
 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.

* string = obj.GetClassName ()
* int = obj.IsA (string name)
* vtkSpline = obj.NewInstance ()
* vtkSpline = obj.SafeDownCast (vtkObject o)
* obj.SetParametricRange (double tMin, double tMax) - Set/
  Get the parametric range. If not set, the range is
  determined implicitly by keeping track of the (min,max)
  parameter values for t. If set, the AddPoint() method will
  clamp the t value to lie within the specified range.
* obj.SetParametricRange (double tRange[2]) - Set/Get the
  parametric range. If not set, the range is determined
  implicitly by keeping track of the (min,max) parameter
  values for t. If set, the AddPoint() method will clamp the
  t value to lie within the specified range.
* obj.GetParametricRange (double tRange[2]) const - Set/Get
  the parametric range. If not set, the range is determined
  implicitly by keeping track of the (min,max) parameter
  values for t. If set, the AddPoint() method will clamp the
  t value to lie within the specified range.
* obj.SetClampValue (int ) - Set/Get ClampValue. If On,
  results of the interpolation will be clamped to the min/
  max of the input data.
* int = obj.GetClampValue () - Set/Get ClampValue. If On,
  results of the interpolation will be clamped to the min/
  max of the input data.
* obj.ClampValueOn () - Set/Get ClampValue. If On, results
  of the interpolation will be clamped to the min/max of the
  input data.
* obj.ClampValueOff () - Set/Get ClampValue. If On, results
  of the interpolation will be clamped to the min/max of the
  input data.
* obj.Compute () - Compute the coefficients for the spline.
* double = obj.Evaluate (double t) - Interpolate the value
  of the spline at parametric location of t.
* int = obj.GetNumberOfPoints () - Return the number of
  points inserted thus far.
* obj.AddPoint (double t, double x) - Add a pair of points
  to be fit with the spline.
* obj.RemovePoint (double t) - Remove a point from the data
  to be fit with the spline.
* obj.RemoveAllPoints () - Remove all points from the data.
* obj.SetClosed (int ) - Control whether the spline is open
  or closed. A closed spline forms a continuous loop: the
  first and last points are the same, and derivatives are
  continuous.
* int = obj.GetClosed () - Control whether the spline is
  open or closed. A closed spline forms a continuous loop:
  the first and last points are the same, and derivatives
  are continuous.
* obj.ClosedOn () - Control whether the spline is open or
  closed. A closed spline forms a continuous loop: the first
  and last points are the same, and derivatives are
  continuous.
* obj.ClosedOff () - Control whether the spline is open or
  closed. A closed spline forms a continuous loop: the first
  and last points are the same, and derivatives are
  continuous.
* obj.SetLeftConstraint (int ) - Set the type of constraint
  of the left(right) end points. Four constraints are
  available:
  0: the first derivative at left(right) most point is
  determined from the line defined from the first(last) two
  points.
  1: the first derivative at left(right) most point is set
  to Left(Right)Value.
  2: the second derivative at left(right) most point is set
  to Left(Right)Value.
  3: the second derivative at left(right)most points is Left
  (Right)Value times second derivative at first interior
  point.
* int = obj.GetLeftConstraintMinValue () - Set the type of
  constraint of the left(right) end points. Four constraints
  are available:
  0: the first derivative at left(right) most point is
  determined from the line defined from the first(last) two
  points.
  1: the first derivative at left(right) most point is set
  to Left(Right)Value.
  2: the second derivative at left(right) most point is set
  to Left(Right)Value.
  3: the second derivative at left(right)most points is Left
  (Right)Value times second derivative at first interior
  point.
* int = obj.GetLeftConstraintMaxValue () - Set the type of
  constraint of the left(right) end points. Four constraints
  are available:
  0: the first derivative at left(right) most point is
  determined from the line defined from the first(last) two
  points.
  1: the first derivative at left(right) most point is set
  to Left(Right)Value.
  2: the second derivative at left(right) most point is set
  to Left(Right)Value.
  3: the second derivative at left(right)most points is Left
  (Right)Value times second derivative at first interior
  point.
* int = obj.GetLeftConstraint () - Set the type of
  constraint of the left(right) end points. Four constraints
  are available:
  0: the first derivative at left(right) most point is
  determined from the line defined from the first(last) two
  points.
  1: the first derivative at left(right) most point is set
  to Left(Right)Value.
  2: the second derivative at left(right) most point is set
  to Left(Right)Value.
  3: the second derivative at left(right)most points is Left
  (Right)Value times second derivative at first interior
  point.
* obj.SetRightConstraint (int ) - Set the type of constraint
  of the left(right) end points. Four constraints are
  available:
  0: the first derivative at left(right) most point is
  determined from the line defined from the first(last) two
  points.
  1: the first derivative at left(right) most point is set
  to Left(Right)Value.
  2: the second derivative at left(right) most point is set
  to Left(Right)Value.
  3: the second derivative at left(right)most points is Left
  (Right)Value times second derivative at first interior
  point.
* int = obj.GetRightConstraintMinValue () - Set the type of
  constraint of the left(right) end points. Four constraints
  are available:
  0: the first derivative at left(right) most point is
  determined from the line defined from the first(last) two
  points.
  1: the first derivative at left(right) most point is set
  to Left(Right)Value.
  2: the second derivative at left(right) most point is set
  to Left(Right)Value.
  3: the second derivative at left(right)most points is Left
  (Right)Value times second derivative at first interior
  point.
* int = obj.GetRightConstraintMaxValue () - Set the type of
  constraint of the left(right) end points. Four constraints
  are available:
  0: the first derivative at left(right) most point is
  determined from the line defined from the first(last) two
  points.
  1: the first derivative at left(right) most point is set
  to Left(Right)Value.
  2: the second derivative at left(right) most point is set
  to Left(Right)Value.
  3: the second derivative at left(right)most points is Left
  (Right)Value times second derivative at first interior
  point.
* int = obj.GetRightConstraint () - Set the type of
  constraint of the left(right) end points. Four constraints
  are available:
  0: the first derivative at left(right) most point is
  determined from the line defined from the first(last) two
  points.
  1: the first derivative at left(right) most point is set
  to Left(Right)Value.
  2: the second derivative at left(right) most point is set
  to Left(Right)Value.
  3: the second derivative at left(right)most points is Left
  (Right)Value times second derivative at first interior
  point.
* obj.SetLeftValue (double ) - The values of the derivative
  on the left and right sides. The value is used only if the
  left(right) constraint is type 1-3.
* double = obj.GetLeftValue () - The values of the
  derivative on the left and right sides. The value is used
  only if the left(right) constraint is type 1-3.
* obj.SetRightValue (double ) - The values of the derivative
  on the left and right sides. The value is used only if the
  left(right) constraint is type 1-3.
* double = obj.GetRightValue () - The values of the
  derivative on the left and right sides. The value is used
  only if the left(right) constraint is type 1-3.
* long = obj.GetMTime () - Return the MTime also considering
  the Piecewise function.
* obj.DeepCopy (vtkSpline s) - Deep copy of spline data.


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