What is on the Backside of the Paper? From 2D Sketch to 3D Model

We demonstrate an intuitive and interactive prototype sketching system that reconstructs 3D polyhedrons incrementally from 2D freehand sketch. The system avoids conventional menu interface and provides an interface mimicking pencil and paper that takes 2D freehand sketch as its direct input. The system offers a natural sketching interface by allowing sketching with discontinuous, overlapping and multiple strokes. The input sketch is a natural line drawing with hidden line removed that depicts a 3D object in real world. The system is configured to interpret sketch under isometric view, which is the most popular viewpoint among designers. The system automatically tidies-up the freehand 2D sketch and reconstructs it into a 3D object. The object can then be transformed, which provides immediate feedback to the designers. New sketch can be drawn over the 3D object, and then be reconstructed into 3D by referring to the existing 3D object from the current viewpoint. This method allows the designers add new parts on the ``backside' ' of the initial sketch. The incremental modelling from sketch enables easy reconstruction of complex 3D objects comparing with the current 3D reconstruction algorithms. It also enables a more detailed object to be reconstructed. 3D modelling, freehand sketching, conceptual design, interactive sketching 1