Surface feature constraint deformation for free-form and interactive design

There is an increasing demand in the conceptual design for more intuitive methods for creating and modifying free-form curves and sueaces in CAD ,nodeling systems. The methods should be based not on1.v on the change of the mathematical parameters but almy on the user’s specified constraints and shapes. Thrs paper presents a new surface representation model for ,%ee-form sur$ace deformation representation. The moa’el is a combination of two functions: a displacement fun,:tion and a function for representing an existing NURBS sur$ace called parent sur$ace. Based on the suvace msdel, the authors develop three deformation methods which are named SingleDef(Single-point constraint based deformation method), MultiDef(Multiple-points constraints based deformation method), and FeatDe,f(Feature constraint based deformation method}. The techniques for free-form surface deformation allow conceptual designers to modify a parent surface by directly applyrng point constraints or a sur$ace constraint to the paren,’ surface. The deformation methods are implemented in an experimental CAD system. The results show that designers can easily and intuitively control the sueace shapt!. &?yWOrdS: computer aided geometric design, jke-form deformation, modeling