API Reference > geometry-core > Bspline > BSplineSurface3d > fractionToPointAndDerivatives fractionToPointAndDerivatives Method evaluate the surface at u and v fractions. fractionToPointAndDerivatives(fractionU: number, fractionV: number, result?: Plane3dByOriginAndVectors): Plane3dByOriginAndVectors Parameter Type Description fractionU number u coordinate, as a fraction of the knot range. fractionV number v coordinate, as a fraction of the knot range. result Plane3dByOriginAndVectors optional pre-allocated object for return values. Returns - Plane3dByOriginAndVectors plane with origin at the surface point, direction vectors are derivatives in the u and v directions. Defined in bspline/BSplineSurface.ts Line 718 Last Updated: 12 June, 2024