A sketch based modeling interface for pen input displays

This thesis presents new contributions to the area of pen-based interfaces for 3D shape modeling: (1) a simple but efficient algorithm for segmenting markings of pen input, (2) an interaction framework for pen-based applications, and (3) based on these two, a new 3D modeling environment. The segmentation of pen markings is a hidden difficulty in the development of a penbased application. It is accomplished by referencing only local shape information— specifically, convexity and monotonicity—resulting in on-the-fly segmentation. For the interaction framework, the recognition results of pen marking lead to selectiveor immediate-manipulation. With selective manipulation, the user can safely perform vague ideas as well as, in the end, decide on what an algorithmic inference offers; the interaction framework is designed not to override the user’s intention. Meanwhile, the immediate manipulation is reserved for more behavioral operations, such as sweeping and transformations. Since the geometric ambiguity prevails while mapping 2D pen markings into 3D geometric shapes, a parametric modeling style has been adopted; shape parameters of the final 3D model are directly manipulated by the user. Using this interaction framework, we propose a new pen-based 3D modeling environment.