Fluid sketching of directed graphs

We describe a prototype sketch-based system that allows users to draw and manipulate directed graphs using gestural input exclusively. The system incorporates the notion of fluid sketching, which attempts to recognize and beautify what the user is drawing while it is being drawn. This concept applies to both the drawing of vertices, which are morphed to circles, and to the drawing of edges, which are approximated on-the-fly by a constrained projection onto low-order polynomials. Consequently, all user-drawn strokes are cleaned up by continuously morphing or projecting them to the nearest geometrically precise shapes. The system has a unique look and feel in that the currently-displayed graph is always at or in transition toward a clean and precise representation of what the user has drawn or is in the process of drawing. When vertices of the graph are dragged to new locations or edges are reshaped, the original graph connectivity is maintained while simultaneously retaining some of its original user-drawn character, such as vertex size and placement, and overall edge shape.