TYPE: VOP
TITLE: Spline VOP

This operator computes either a Catmull-Rom (Cardinal) spline or a Linear spline
between the specified key points, given an interpolant (u) in the domain of the
spline. The result is a 1D, 3D, or 4D value representing u's image on the
spline.

The Cardinal keys are uniformly spaced over the range 0 to 1. Because of the
nature of the Cardinal spline, the value associated with the first and last
keys will never be returned. However, these keys are used to determine the
shape of the curve on entry and exit. If you want the spline to reach its end
points, connect the first key and last key twice. See the Fire operator for one
such example.

If you are blending only two vector types using the Cardinal interpolant, the
Color Mix operator offers the convenience of fewer connections. Make sure,
however, that you choose the "Smooth With Cardinal Spline" option to obtain the
exact same results as with this operator.

The Linear spline interpolation is equivalent to a sequence of Linear
Interpolation operators. Consider the simpler Mix operator if only two inputs
are required.

Parameters:
    Spline                - Catmull-Rom (Cardinal) or Linear.

Inputs:
    Parametric Coordinate - Interpolant (u) representing the parametric location
                            in the domain of the spline where to evaluate the
                            spline.
    Input Number 1...N    - 1D, 3D or 4D spline key points to interpolate.
    Next Input            - Where the next key value should be connected.
                            Up to 64 inputs can be specified.

Outputs:
    Combined Value        - Interpolated spline location.

See also: Blend Regions(blendregions), Color Mix(colormix), Fire, Mix, Shift,
          Smooth
