Geometric modeling is a fundamental problem in computer graphics. The continuous growth of 3D models in public repositories has shifted research focus from computing local, low-level geometry features such as curvature and textures to high-level semantic information such as shape parts information and shape structural characteristics (symmetry, parallelism, etc.). However, automatically computing such semantic information is essentially an ill-posed problem due to the ambiguities in the definition of shape semantics....[ Read more ]

Geometric modeling is a fundamental problem in computer graphics. The continuous growth of 3D models in public repositories has shifted research focus from computing local, low-level geometry features such as curvature and textures to high-level semantic information such as shape parts information and shape structural characteristics (symmetry, parallelism, etc.). However, automatically computing such semantic information is essentially an ill-posed problem due to the ambiguities in the definition of shape semantics.

This thesis focuses on developing interactive approaches to aid the shape analysis process. We leverage user assistance to exploit shape semantics, and to respect and preserve them during manipulation. In particular, this thesis aims at advancing state-of-the-art interactive techniques in two specific geometric applications: shape segmentation and shape manipulation.

First, we introduce two interactive tools for shape segmentation, which we call cross-boundary brushes and dot scissor. Both tools offer very simple and easy-to-use user interfaces that operate at interactive rates. In contrast to existing state-of-the-art interactive segmentation tools, our tools allow the user to cut out meaningful and functional components in most cases using only a single mouse stroke or click near boundary regions, making them very convenient to use. We adopt the concept of isolines of harmonic fields as cutting boundaries in designing both tools. We show that the propagation properties and the differentiating power of the harmonic fields allow effective computation of shape semantic boundaries for segmentation purposes.

Second, we developed an editing framework that first extracts the shape’s structural features and preserves them during user manipulation. In contrast to traditional shape editing frameworks, the system operates at the component level and takes a shape’s structural characteristics such as inter-relations among semantic components as modeling constraints, enabling an effective structure-preserving editing tool. We show that user assistance is essential in accurately revealing complex shape structures. We use a semi-automatic shape segmentation process as a prior step to facilitate the analysis of shape structures and inter-relations, and show that these shape analysis results play an important role in preserving a shape’s global features during user manipulation.