Hierarchical feature subspace for structure-preserving deformation

This paper aims to propose a new framework for structure-preserving deformation, which is interactive, stable, and easy to use. The deformation is characterized by a nonlinear optimization problem that retains features and structures while allowing user-input external forces. The proposed framework consists of four major steps: feature analysis, ghost construction, energy optimization, and reconstruction. We employ a local structure-tensor-based feature analysis to acquire prior knowledge of the features and structures, which can be properly enforced throughout the deformation process. A ghost refers to a hierarchical feature subspace of the shape. It is constructed to control the original shape deformation in a user-transparent fashion, and speed up our algorithm while best accommodating the deformation. A feature-aware reconstruction is devised to rapidly map the deformation in the subspace back to the original space. Our user interaction is natural and friendly; far fewer point constraints and click-and-drag operations are necessary to achieve the flexible shape deformation goal. Various experiments are conducted to demonstrate the ease of manipulation and high performance of our method. (C) 2012 Elsevier Ltd. All rights reserved.