API Reference > geometry-core > Bspline > BSpline2dNd > fractionToRigidFrame fractionToRigidFrame Method evaluate the surface at u and v fractions. Return a (squared, right handed) coordinate frame at that point on the surface. fractionToRigidFrame(fractionU: number, fractionV: number, result?: Transform): undefined | Transform Parameter Type Description fractionU number u parameter fractionV number v parameter result Transform undefined if surface derivatives are parallel (or either alone is zero) Returns - undefined | Transform Defined in bspline/BSplineSurface.ts Line 277 Last Updated: 12 June, 2024