CenterStageObject Class:  CurveFromCurve
Subclass of:  Curve
Requires reference to a Curve object

The CurveFromCurve lets you create a Curve object that relates to
another curve object.  The reference curve value is computed and is
used as the origin for the referring object at each value of the
parameter.  The CurveFromCurve's function is computed and the result
is added to the original curve's value, either in absolute
coordinates, in in relation to the curve's Frenet frame.

In addition to the standard Curve directives, CurveFromCurve supports
the following:

   Function param func [-frame | -absolute]

	Here the "param" and "func" arguments are the same as for the
	standard Curve.  The -frame and -absolute options determine
	whether the result of the function is in the coordinate system
	of the Frenet frame for the linked curve or in absolute
	coordinates (the default).  If -frame is provided, then both
	curves must be in 3-space, and the Frenet frame is computed
	numerically.  The x, y and z coordinates correspond to the
	tangent, normal and binormal directions.

	For example:

		Function {t} {
		  let (T,N,B) = (0,d,0)
		} -frame

		Axes {T N B}

		Slider d 0 2

	produces a curve that is the offset curve to the original
	along the normal direction.  The offset distance is given by a
	slider, so a family of offset curves can be investigated.


    Domain {Inherit}
	
	This special form of the domain command can be used to inherit
	the domain from the original curve.  Standard Domain
	specifications can also be used to provide a domain other than
	the one of the original curve.
