This function returns a value picked from a spline by the scalar C.
The value returned will of the same data type as the knots, K.
The curve fits an interpolatory spline to the knot inputs.

This input must be a scalar.
It is the controller, used to pick the return value on the spline.

These are knots in the spline.
The knots may be scalars, vectors, or colors.
All knots must be of the same data type.

This function returns a value picked from a curve by the scalar C.
The value returned will of the same data type as the knots.
The curve fits an interpolatory spline to the knot inputs.