A Constraint-Based Method for Sculpting Free-Form Surfaces

We discuss the problem of adding features to a free form surface by applying one or several user deened surface curves. The curves are seen as editable parameters, while the surface is to be changed automatically, keeping a prede-ned set of constraints satissed, speciically the curve{surface incidence and derivatives. We review and update our approach presented earlier 18] and show, how the curve{surface composition can be expressed as a linear transformation. We describe the so{called \aliasing" eeect caused by an incompatibility of a general curve on a surface with the rectangular mesh of degrees of freedom of a tensor product surface. A solution is proposed by locally changing the parametrization of the original surface which takes a domain curve to an iso{ line in either parameter direction.