TANGICAD: TANGIBLE INTERFACE FOR MANIPULATING ARCHITECTURAL 3D MODELS SHERIF M. ABDELMOHSEN & ELLEN YI-LUEN DO College of Architecture, Georgia Institute of Technology, 247 Fourth Street, Atlanta, GA 30332-0155, USA sherif.morad@gatech.edu, ellendo@gatech.edu Abstract. This paper presents an interface for interacting with tangible objects to produce and edit architectural 3D models, called TangiCAD. TangiCAD is a tangible/virtual construction kit which allows architects to manipulate virtual models using easy hand control of tangible cubes, as an alternative interface for 3D modeling. It consists of a set of tangible cubes representing architectural elements, such as walls, columns, slabs,…etc., in addition to some editing operations. With more developed versions, the paper argues that architects could use tangible interfaces to carry out 3D modeling in an intuitive way, using their "flip-the-box" hands-on movement. 1. Motivation Tangible blocks are significant tools for manipulation, especially with architects and designers, who prefer hand manipulation and physical interaction with tangible models rather than graphical user interfaces (GUIs). Evidence has shown that tangible user interfaces (TUIs) have more positive effects on designers’ spatial cognition, perception and reasoning for visuo- spatial information (Kim and Maher, 2006; Sharlin et al., 2002). Kim et al. (2005) argue that TUIs are usually passive elements, hardly manipulated and interpreted by computers once arranged in a tangible setting. The manipulation and visualization of virtual building models, however, is limited by the use of graphical display constraints such as the visual screen, keyboard and mouse. Confusion and delay can occur along the shifted focus between computer controls and represented data, thus decreasing focus on the model configuration instead of the tools used to build it. TangiCAD, shown in Figure 1, has attempted to address the issue of achieving best results out of both GUIs and TUIs. TangiCAD was designed for the purpose of addressing the virtue of manipulating blocks physically and the virtue of enclosing design alternatives virtually for future modification, comparison of alternatives, and digitally representing the built model. It takes advantage of the human ability to easily manipulate tangible objects which represent a corresponding "wall", "column", or "slab" in the virtual world. It also provides effortless and easy hand tactile interaction with tangible objects to generate diverse design alternatives for tangible