Inordertomeettheneedsofpracticaldesign,aninterpolationtechniqueisemployedtoconstraintheshapeofsurfaces.Themethodofpreservingpositivityontheinterpolationsurfaceandconstraintoninterpolatingdataisalsodeveloped.Theadvantageofthisnewmethodisthatitcanbeusedtoconstraintheshapeofaninterpolatingsurfaceonlybyselectingsuitableparameters,andnumericalexamplesarepresentedtoshowtheperformanceofthemethod.