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In spite of the recent advances in computer-aided design, the quest of designing free-form shapes that are aesthetically pleasing and functionally satisfactory remains challenging for industrial designers. One of the obstacles is the lack of the computational support for the fluid externalization of aesthetic features, and the automatic preservation of engineering constraints during early conceptual design. Instead, the current technology forces designers to fiddle with indirect shape proxies such as control cages, or incremental shape modifiers such as digital sculpting tools, and engage in the redundant, laborious work flows such as topology preparation or constraint satisfaction, which significantly diverts the designers’ time and cognitive resources away from aesthetic ideation. Such issues are rooted in the constructive nature of the current shape modeling tools. In this work, I propose that such obstacles can be negotiated by prescriptive geometric modeling with user-specified constraints. At the heart of this methodology is a division of labor be- tween the human users and the computer that has taken into account the iterative nature of early product design. With prescriptive modeling tools, the designers focus solely on expressing the desired aesthetic features and engineering constraints, both in the forms of hand-drawn curves and annotations; the computer interprets such input, and synthesizes or modifies the shape under edit to fulfill the prescriptions, such that the resulting shape interpolates the feature curves, and conforms to the engineering constraints. In doing so, we seek to achieve a streamlined conceptualization work flow with the pen-and-paper fluidity, keep the designer focused by offloading many distractive processes to the computer, and reduce potential downstream conflicts by introducing engineering constraints early in conceptual design. The prescriptive approach is embodied in several systems servicing different stages and tasks during early conceptual design. First, I present a streamline-based shape modeling system. With this system, users are able to design a smooth ensemble of on-surface streamlines by sketching a few constraint curves, and subsequently use the streamlines to scaffold further construction of 3D free-form features that “flow” on the base surface. Then, I present a shape modeling system that allows the user to edit the features via direct manipulation, while preserving user-specified aesthetic design intentions, as well as engineering constraints manifested as spatial dimensions. Finally, I describe the integration of the described systems into existing modeling tools, and present a user study to validate the effectiveness.
Luoting Fu. (2013). Geometric Modeling for Industrial Design with User-Prescribed Constraints. PhD thesis. Carnegie Mellon University, USA.