TUI-Geometry: A Tangible User Interface for Geometric Drawing on an Interactive Tabletop

Physical drawing tools, such as rulers, afford immediate visual and proprioceptive feedback to the user: even before a line is added to the drawing. Such immediacy is not available in standard digital drawing software. We introduce TUI-Geometry, a drawing application that senses tangible drawing tools on an interactive tabletop and provides the user with intelligent visual feedback and drawing beautification. A user evaluation comparing TUI-Geometry to an application with passive tools showed that users preferred TUI-Geometry and were able to draw significantly more accurately with it -- thus we provide the foundation for intelligent instructional support of geometry construction with tangibles.