James Gain

PhD Research

Virtual Sculpting

Directly manipulated free-form deformation is a powerful interactive modelling technique, which transforms an object by warping the surrounding space. DMFFD allows a designer to move object points directly and have the surface conform smoothly. We address several problems with the use of the basic algorithm in virtual sculpting.

Refinement and decimation

Basic DMFFD degrades the visual quality of a polygon mesh object when flat, sparsely faceted regions become sharply curved. A curvature-based adaptive refinement and decimation technique has been developed.

Fig1: A Sequence of deformations

Without refinement/decimation

With refinement/decimation

First derivative manipulation

Controlling deformations by using only simple constraints, consisting of points and their intended motion, is restrictive. We have extended the control of DMFFD by developing first derivative manipulation.

Fig 2: First derivative manipulation: Undeformed, Tilting, Scaling, Twisting

Curve-based manipulation

Another enhancement is to allow the user to specify curves on or within the object and use these as tools for deformation.

Preventing self-intersection

A serious shortcoming of basic DMFFD is that some deformations cause the object to intersect itself. We prevent this by identifying illegal constraints and then breaking them into smaller steps.

Fig 3: Preventing self-intersection: Two initial objects with constraints, basic DMFFD, Subdivided constraints prevent self-intersection.

This research aims to enhance the versatility, efficiency, ease-of-use and correctness of the directly manipulated free-form deformation technique.


Last updated March 2001