Deformable modeling using generalized curve constraints

Abstract

For simultaneous deformations of multiple surfaces, a constraint called a link constraint is created to link two faces that are to be deformed together. The link constraint consists of a relationship between a constraint curve in each face to be deformed. The selected constraint curve may be any curve, including trimmed curves and part of a boundary curve. As the faces are deformed, the link constraint limits the deformation of the faces by acting as a zipper between the two surfaces along the selected constraint curve. For local deformations within a surface, a hierarchy is created within specific areas, known as patches, of an individual face in a model, ensuring that when a patch in the hierarchy is deformed, the deformation affects patches lower in the hierarchy than that patch, but the deformation does not affect patches higher in the hierarchy. A constraint curve known as a seam, which may be any simple closed loop curve, is used to define the relationship between a patch, known as a parent patch, and a patch directly below that patch in the hierarchy, known as a child patch. For each seam, a seam constraint is created which limits the deformation of the associated child patch and all its children by forcing the child patch to maintain connectivity with its parent patch along the seam.