What is on the backside of the paper? From 2D sketch to 3D model

We demonstrate an intuitive and interactive sketching system that reconstructs 3D object incrementally from 2D freehand sketch. The system avoids conventional menu interface and provides 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 designer. 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 designer adds new parts on the ``backside'' of the initial sketch. The incremental modelling from sketch enables easy reconstruction of sophisticated 3D object comparing with the current 3D reconstruction algorithms. It also enables a more detailed object to be reconstructed.