CIGRO: A minimal instruction set calligraphic interface for sketch-based modeling

Abstract. Although CAD systems have evolved considerably in functionality, expressiveness and modeling power over the last decades, their user interfaces are still tied to legacy principles and are not suited to the initial stages of prod-uct development. They exhibit steep learning curves, cumber-some and overly structured dialogues, including hundreds of commands. While much of this functionality may be required by the sheer complexity of the tasks these sys-tems are designed to help, we believe the user interface could benefit from sim-pler paradigms based on sketching and drawing to reduce unneeded complex-ity, especially in the conceptual design phase. In what follows, we present the CIGRO system that provides a reduced instruction set calligraphic interface to create polyhedral objects using an incremental drawing paradigm evocative of paper and pencil drawings. Users draw polylines on an axonometric projection, which are automatically beautified and connected to existing parts of the draw-ing. Such line drawings are then converted to a three-dimensional model through a reconstruction process guided by an axonometric inflation method.