Context dependent digital shape editing in product design

The present CAID systems insufficiently support designers with effective and intuitive tools for shape modelling. Designers' efficiency significantly decreases when shape alterations are performed. The research described in this thesis deals with the development of a methodology to support more effectively and efficiently the industrial designers during their digital shape editing processes. A series of modelling experiments have been conducted to analyse differences between the expert and the non-expert users, their preferences in terms of entity usage, drawbacks in workflows, and to investigate opportunities for the improvement of the design process. A shape context concept has been proposed based on which shape editing tools incorporating only the desired collection of shape variation procedures, parameters and constraints are provided to the user. By cancelling the unnecessary degrees-of-freedom, users can play with their shapes within specific shape domains until the shape satisfying the design requirements is reached. Based on the shape context description and the results from the modelling experiments, two contextual shape editing tools were developed and implemented into a commercial shape modelling system. Through slide-bar controlled morphing-like editing, users transform a source shape into a target shape. Usability testing was carried out to investigate both users' efficiency and acceptance of the shape context concept. A shape context methodology was then proposed so that user-defined parameters can also be supported. Visual perception theory and the results from the modelling experiments were considered. The 3D objects are considered decomposed into meaningful components and so the topological constraints are readily available. The component to be deformed is abstracted by a skeletal representation and a set of contours. Two existing shape composition rules were studied for the definition of revolution-like and sweep-like target surfaces. The user-defined parameter is represented by a profile curve that corresponds to either the path or the profile of the target surface. The skeletal representation remains unchanged during the shape editing preserving proper correspondence between the source and the target surfaces. The results presented in this thesis demonstrate that the digital design process improves if contextual shape editing tools are provided to designers. The process becomes more efficient and effective when tools based on user-defined parameters and the objects' structures are applied. In addition, the designer's creativity is stimulated by the increased range of shapes generated and visualised through the continuous transformation of the source shape into the target shape