setCurve( index, curveNo ) {

			if ( isNaN( curveNo ) ) throw Error( 'curve index being set is Not a Number (NaN)' );
			this.whichCurve[ index ] = curveNo;
			this.writeChanges( index );

		}
Select which curve to use for an element

@param {number} index the index of the instanced element to update
@param {number} curveNo the index of the curve it should use