API Reference > geometry-core > Curve > CurvePrimitive > fractionToPointAndDerivative fractionToPointAndDerivative MethodAbstract Return the point (x,y,z) and derivative on the curve at fractional position. Note that this derivative is "derivative of xyz with respect to fraction." this derivative shows the speed of the "fractional point" moving along the curve. this is not generally a unit vector. use fractionToPointAndUnitTangent for a unit vector. fractionToPointAndDerivative(fraction: number, result?: Ray3d): Ray3d Parameter Type Description fraction number fractional position along the geometry. result Ray3d Returns - Ray3d Returns a ray whose origin is the curve point and direction is the derivative with respect to the fraction. Defined in core/geometry/src/curve/CurvePrimitive.ts Line 102 Last Updated: 13 June, 2024