Interpolation methods: the Lagrange parabola (solid) does not give a good representation of the run of S along the short characteristic from S₀ to S₁. Parabolic monotonic Bézier interpolation (dashed) is achieved by restricting the control point c₀ (defined by the two tangents (dotted) of each parabola) to S₀ <  = c′₀ <  = S₁.