The creation and modification of 3D models using sketches and curves

This chapter describes interfaces and algorithms that support a potentially untrained user's intent to communicate a mental model of 2D/3D shape to a digital computer; FiberMesh for the creation, and SilSketch for the modification of 3D shapes. Fiber- Mesh is a system for designing freeform surfaces with a collection of 3D curves. The user first creates a rough 3D model by using a sketching interface. The user-drawn strokes stay on the model surface and serve as handles for controlling the geometry. For a given set of curves, the system automatically constructs a smooth surface embedding by applying functional optimization. SilSketch is an over-sketching interface for feature-preserving surface mesh editing. The user sketches a stroke that is the suggested position of part of a silhouette of the displayed surface. The overall algorithm has been designed to enable interactive modification of the surface-yielding a surface editing system that comes close to the experience of sketching 3D models on paper. While machines are equipped with clearly defined interfaces for video input (cameras, scanners) and output (monitors, projectors), human beings are not. In fact there is quite an imbalance at work here; while one could argue that the human visual system is currently superior to the video-in of a machine, we lack a clear definition of the human video-out. The most common ways of communicating and/or creating 2D/3D shapes are either using hand-drawn 2D sketches, or modeling 3D shapes with malleable materials such as clay. Unfortunately, these means of communication and creation are generally limited to a small subset of artistically trained individuals. In the following we describe our interfaces and algorithms, which are designed to assist the user with meaningful and intuitive operations and thereby alleviate the described shortcomings.