From Explicit to Implicit Surfaces for Visualization, Animation and Modeling

Deformable 3–D models are used extensively in Computer Graphics and Computer Vision for Visualization, Animation and Modeling. They can be represented either as traditional explicit surfaces, such as triangulated meshes, or as implicit surfaces. On one hand, explicit surfaces can easily be manually deformed by users, such as graphics designers, either directly by moving the mesh vertices or indirectly using a Free Form Deformation approach. On the other hand, implicit representations are well-suited both for physically-based simulations and for modeling noisy image-data. For example, to fit a cloud of 3–D points, implicit representations allow fitting without search because one only needs to evaluate a differentiable field function at every data point, instead of searching for the facets that are closest to the data points. In this paper we propose a method that can turn an explicit surface into an implicit shell, which closely approximates its shape and can deform in tandem with it. This allows both graphics designers to deform and reshape the implicit surface by manipulating explicit surfaces using standard deformation techniques and automated fitting algorithms to take advantage of the attractive properties of implicit surfaces. We demonstrate the applicability of our technique for upper body—head, neck and shoulders—modeling and animation.