Smoothing operations on a three-dimensional geometrical primitive, such as a mesh, are restricted by filtering the set of smoothing vectors to apply a user-selected restriction to the set of vectors. The user-selected restriction limits the set of smoothing vectors according to a normal of a surface corresponding to the primitive. The filtered set of vectors are applied to the primitive to smooth the primitive. Thus, smoothing may be applied proportionally to the convexity or concavity of the surface. Smoothing also may be applied to move a control point of the primitive, such as a vertex in a mesh, only in a direction parallel to the normal of the surface at that control point or perpendicular to the normal of the surface at that control point. Each control point also may be reprojected after smoothing onto the original surface along the normal of the smoothed surface, or the normal of the original surface.