Hau Hing Chau

EVALUATION OF A 3D SHAPE GRAMMAR IMPLEMENTATION

The geometric design of the exterior appearance of consumer products is a principal consideration to retain brand identity. Architectural and engineering shape grammars had demonstrated shape computation as a formal and viable approach for supporting style conformance. However, most existing shape grammar implementations operated in limited experimental domains, and lacked support for complex three dimensional geometry, shape emergence and parametric shape rules. The aim of the reported research is to address these issues. Shape algebras are reduced in terms of shape operations with their basic elements which is generally applicable to shape computation. Specifically for algebra U13, exhaustive cases were enumerated for shape sum and shape difference operations. A U13 shape grammar implementation was developed to support both rectilinear and curvilinear basic elements in three dimensional space. Mathematical representations of basic elements were based on non-uniform rational b-splines and their reduced form. This allowed a simple yet exact notation which simplified support for maximal representation and its computation. Two cases studies, a Coca-Cola bottle grammar and a Head & Shoulder bottle grammar, were used to test the implementation.

Computer Aided Design: An Early Shape Synthesis System

Today’s computer aided design systems enable the creation of digital product definitions that are widely used throughout the design process, for example in analysis or manufacturing. Typically, such product definitions are created after the bulk of [shape] designing has been completed because their creation requires a detailed knowledge of the shape that is to be defined. Consequently, there is a gulf between the exploration processes that result in the selection of a design concept and the creation of its definition. In order to address this distinction, between design exploration and product definition, understanding of how designers create and manipulate shapes is necessary. The research outlined in this paper results from work concerned with addressing these issues, with the long term goal of informing a new generation of computer aided design systems which support design exploration as well as the production of product definitions. This research is based on the shape grammar formalism.

Computer-aided design synthesis: an application of shape grammars

Computer-aided design systems enable the creation of digital product definitions that are widely used throughout the design process. Typically, such product definitions are created after the bulk of [shape] designing has been completed because their creation requires a detailed knowledge of the shape that is to be defined. Shape grammars have been applied in a range of domains to generate design shapes that conform to a given style early in design processes. A key challenge that restricts their implementation lies in the detection of embedded shapes, sub-shapes, which are manipulated according to shape rules to create new shapes. The automatic detection of sub-shapes is an open research question within the shape grammar community. The research reported in this paper explored the use of computer vision techniques to address this problem; the results achieved to date show real promise. An early prototype is presented and demonstrated on a designers sketches.

Exploiting lattice structures in shape grammar implementations

Abstract The ability to work with ambiguity and compute new designs based on both defined and emergent shapes are unique advantages of shape grammars. Realizing these benefits in design practice requires the implementation of general purpose shape grammar interpreters that support: (a) the detection of arbitrary subshapes in arbitrary shapes and (b) the application of shape rules that use these subshapes to create new shapes. The complexity of currently available interpreters results from their combination of shape computation (for subshape detection and the application of rules) with computational geometry (for the geometric operations need to generate new shapes). This paper proposes a shape grammar implementation method for three-dimensional circular arcs represented as rational quadratic Bézier curves based on lattice theory that reduces this complexity by separating steps in a shape computation process from the geometrical operations associated with specific grammars and shapes. The method is demonstrated through application to two well-known shape grammars: Stinys triangles grammar and Jowers and Earls trefoil grammar. A prototype computer implementation of an interpreter kernel has been built and its application to both grammars is presented. The use of Bézier curves in three dimensions opens the possibility to extend shape grammar implementations to cover the wider range of applications that are needed before practical implementations for use in real life product design and development processes become feasible.

Embedding Design Descriptions Using Lattice Structures: Technical Requirements, User Perspectives and Implementation

Commercially available engineering design tools typically operate on native data formats and support individual designers creating design descriptions which are shared within product development teams and across supply networks. The use of such tools results in a multiplicity of design descriptions. For example, a CAD system may be used to create a design Bill-of-Materials (BoM), which is a form of design description, but different BoMs are needed for downstream processes such as manufacturing and servicing. Conventional approaches to the integration of design descriptions is through the use of data exchange technologies or a common underlying meta-model to support, ultimately, a single, shared digital design description. These approaches have architectural elegance but their real-world feasibility is limited by the heterogeneous environment in which they must be implemented. The research reported in this paper challenges this thinking and explores the feasibility of embedding design descriptions into each other. We report early results exploring the feasibility of using lattice theory, where lattices are in the form of partially ordered sets, to embed multiple design structures into a given design description.

Interactions between Brand Identity and Shape Rules

Brand and the maintenance of brand identity are key drivers in consumer product development activities. This paper aims to give early results of research that sits between marketing and shape computation technologies. An initial review of brand identity from a marketing perspective is presented along with an analysis from student designers in identifying brand characteristics of consumer products. Results of early experiments with a prototype computational design synthesis system are reported.