Computer graphics techniques for modeling page turning

摘要

Turning the page is a mechanical part of the cognitive act of reading that we do literally unthinkingly. Interest in realistic book models for digital libraries and other online documents is growing. Yet, actually producing a computer graphics implementation for modeling page turning is a challenging undertaking. There are many possible foundations: two-dimensional models that use reflection and rotation; geometrical models using cylinders or cones; mass-spring models that simulate the mechanical properties of paper at varying degrees of fidelity; and finite-element models that directly compute the actual forces within a piece of paper. Even the simplest methods are not trivial, and the more sophisticated ones involve detailed physical and mathematical models. The variety, intricacy, and complexity of possible ways of simulating this fundamental act of reading is virtually unknown. This article surveys computer graphics models for page turning. It combines a tutorial introduction that covers the range of possibilities and complexities with a mathematical synopsis of each model in sufficient detail to serve as a basis for implementation. Illustrations are included, which are generated through our implementations of each model. The techniques presented include geometric methods (both two- and three-dimensional), mass-spring models with varying degrees of accuracy and complexity, and finite-element models. We include a detailed comparison of experimentally determined computation time and subjective visual fidelity for all the methods discussed. The simpler techniques support convincing real-time implementations on ordinary workstations. We also address the question of whether suchrntechniques are worthwhile in practice by describing results from a user study that compared the performance of a page-turning book model with HTML and PDF presentations of the same material-and with physical books. This demonstrates that the book model has many advantages over conventional document formats.