Free Form Modeling with History
Geoff Wyvill, Dean McRobie, Chris Haig, Craig McNaughton · International Journal of Shape Modeling · 1996
We present a new kind of surface made by a hybrid of parametric mapping and free form deformation. The surface is mapped from an original parametric space, and then subjected to a sequence of deformation operations. Rather than express the deformations with a global grid, they are described as a sequence of local operations. The surface shape is thus defined by the history of operations that formed it.Each of these deformation operations is encapsulated in a structure of control information known as a 'feature'. Features are manipulated by means of reference points on the surface known as handles and by means of widgets that alter their properties. The calculation of the surface from this structure is very efficient and permits interactive display of complex models.The result of this approach is that we have been able to build an interactive modeler for free form surfaces with a remarkably natural feel. The user directly manipulates a block of infinitely stretchable plastic clay.Because the surface is continuously mapped from a parametric space, it is easy to add solid texture. The surface can be further deformed after texturing, maintaining a correspondence between texture and surface features.