A language for representing and extracting 3D geometry semantics from paper-based sketches

Abstract

Every product that exists, ranging from a toothbrush to a car, has first been conceived as a

mental concept. Due to its efficacy in rapidly externalizing concepts, paper-based

sketching is still extensively used by practising designers to gradually develop the

three-dimensional (3D) geometric form of a concept. It is a common practice that form

concepts are sketched on paper prior to generating 3D virtual models in commercial

Computer-Aided Design (CAD) systems. However, the user-interface of such systems does

not support automatic generation of 3D models from sketches. Furthermore, the inherent

characteristics of form sketching (e.g. idiosyncrasy) pose a challenge to computer-based

understanding of the form concept semantics expressed on paper. To address these issues,

this paper is therefore concerned with the development of a visual language that is

prescribed and to be used by product designers to annotate paper-based sketches such

that the form geometry semantics can be formally represented; parsing the annotated

sketch allows for the automatic generation of 3D virtual models in CAD. Inspired by re- usable 3D CAD modelling functions and the related environmental constraints and

requirements, a prescribed sketching language, PSL, has been developed to annotate

paper-based form sketches. The framework architecture which parses the annotated

sketch and subsequently extracts the form concept semantics is described. Based on this

framework, a prototype computer tool has been implemented and evaluated. Evaluation

results provide a degree of evidence, first on the suitability of PSL in representing the

semantics of a range of forms, and secondly on the designers' acceptance of taking up this

annotated sketching approach in practice.