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theses

In this dissertation I present methods for interactive creation and deformation of 3D shapes. For high-quality free-form deformation of polygonal meshes I introduce a hybrid approach that combines cage-based and surface-based shape editing paradigms. The continuum between purely surface-based and purely cage-based methods is explored by applying as-rigid-as-possible surface modeling to an automatically simplified version of an input mesh. The original shape is updated using precomputed weights based on mean value coordinates on this simplified mesh. This allows to exploit the speed of the cage-based approaches and retain the ease of use of surface-based methods while requiring no extra footwork from the user. Thereafter I present algorithms for creating ready-to-animate rigged 3D models from 2D sketches. The input user sketch is treated as the silhouette of the desired shape, and the system generates a surface composed of smoothly joined generalized cylinders, a bone skeleton, and skin weights attaching the surface to the skeleton. For the skeleton creation I introduce a generalized version of the Douglas-Peucker line simplification algorithm. This unified approach to modeling and rigging, when augmented with merging and cutting operations, greatly simplifies the traditionally sequential 3D character animation pipeline and removes friction from incremental and iterative character modeling and animation. Finally I extend this approach to models with flexible parts by introducing a spline based skeletal deformation technique. The curve skeleton of the shape is represented by series of cubic splines, whose end points serve as the joints of the bone skeleton. When the bone skeleton is manipulated, the end points follow the joints, and tangents and twists at the end points are computed from the transformations of the adjacent bones and respecting the nature of coupling between the corresponding parts of the shape. Similarly to traditional skinning the deformed surface is given by a weighted blending, but combining transforms of curve points instead of those of bones. Users can pose their models using a sparse bone skeleton, without the need for manually constructing higher level controls. The presented methods bring 3D modeling closer to non-professional users and enable them to express themselves creatively. At the same time they can help artists quickly try out ideas and speed up prototyping.

ETD_5286

Ph.D.

Includes bibliographical references

by Péter Borosán

doi:10.7282/T3028PNM

ETD doctoral

The author owns the copyright to this work.