A Graph-Matching Approach to Sketch-Based Modelling Filipe Marques Dias Joaquim A. Jorge Department of Information Systems and Computer Science INESC-ID/IST/Technical University of Lisbon R. Alves Redol, 9, 1000-029 Lisboa, Portugal fil@immi.inesc-id.pt, jorgej@acm.org Abstract Automobile designers, when creatively designing a vehicle, have to bind by several shape constraints while also exploring new concepts. A natural and unhindered modelling environment for a designer to start modelling in is thus desired. We present our ongoing modelling system, AutoMake, that enables calligraphic modelling of a simple 3D object that resembles the body shape of a car. Our system provides an innovative way to recognize 3D objects by matching sketches against templates stored in a database, indexed by multiple edge graphs based on various views. Our approach enables users to specify a bounding box providing perspective and size infor- mation about model. The user next sketches a model that is matched against a template, using a multidimen- sional indexing structure. Keywords Sketch-based Modelling, Graph Matching. 1. INTRODUCTION Modelling three-dimensional objects from sketch input has gained importance in the modelling field recently. This fact was motivated by the lack of user-centred con- cerns in modelling systems, preventing users from pour- ing their creative power directly upon 3D models without fiddling with bureaucratic modelling interaction concerns. This hampering of creative use forces the separation of tasks. In the industry, this translates into modelling ex- perts working together with designers, causing a need for comprehensive and delaying communication due to mis- interpretation and other physical impossibility issues [Dias03]. In order to solve this, the designer needs to build an early stage 3D model that can afterwards be re- fined and worked from by the modeller. Furthermore, in those early stages of product design, designers sketch creative drawings to explore ideas and produce rough sketches of objects that are usually bound to some general constrained specifications. This led us to the problem of providing a natural and unhindered modelling environ- ment for a designer to start modelling in. We propose a calligraphic approach, based on 3DSketch [Mitani00, Mitani02, Varlet04], where the user sketches a visible- edge representation of one of several possible template models, and is able to manipulate, and edit it by re- sketching over edges as if correcting their curvature. Our approach allows the designer to draw with stylus and tab- let or directly on screen, with a digitizing monitor, in a similar fashion as sketching on paper. Our approach ap- plies fewer restrictions to models since unknown informa- tion is assumed to be specified by the template stored on the database. The following section takes a look at other approaches in this area and points out their difficulties in completely solving this problem. The next section describes our ap- proach, explaining how our approach sees the template drawing as a graph, and retrieves it from a data structure. The remaining section refers final considerations, ongo- ing work aspects, and directions to take for future devel- opment. 2. RELATED WORK The topic of modelling 3D objects interactively from 2D calligraphic input is becoming a more common in the modelling context. In 1994, IdeS [Branco94] appeared with a modelling scheme based on reconstruction and gesture recognition, for use in a mechanical engineering context. The user was able to draw the solids’ visible edges and issue some modelling commands by means of gestures, like extru- sions, cuts, and other operations involving more objects. Later, this work saw vast improvements, when context- based modelling aid was introduced in its successor, GIdeS [Pereira00]. GIdeS improved on the previous work in many key areas, the main of which: the user interface, and the addition of context-based functionality to cope with the ambiguity natural to reconstruction. The latter is achieved by an ingenious expectation list that presents several previews of the final result depending on the ap- plicability of operations. The modelling approach present in that system reflects the concerns with user interaction, corresponding to a constructive way of modelling. SKETCH [Zelesnik96] introduced another gesture-based interface for approximate 3D modelling, with some added 161 13º Encontro Português de Computação Gráfica 12 - 14 Outubro 2005