Example data cards 

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... desktop graphical interfaces. We assume that many interactions with the information underlying the immersive display will continue to be conducted in traditional desktop-based 2D GUIs. Our system will provide a GUI-based means for easily binding selected digital information onto physical tokens, building on the “monitor slot” approach of [Ullmer et al. 1998]. Users may then simply access and manipulate this content on interaction pads, while their visual focus remains direc- ted toward the main object of interest . In immersive virtual environments, this will often be some form of 3D graphical visualization. In collaborative usage contexts, the object of interest may also be collocated or remote people. We expect that within immersive environments, users may continue to use both generic and specialized 3D pointing devices as the primary tools for spatially manipulating 3D graphical content. Toward this, our interface allows users to hold a 3D tracker in one hand, while using the second hand to engage with the abstract digital information and operations represented by our visualization artifacts. We imagine that truly simultaneous manipulation of both the tracker and visualization artifacts may be infrequent. Nonetheless, we believe this two-handed approach will help minimize the “set-up” and “tear-down” time and distraction of acquiring the tracking device, switching software modes, retargeting to a new spatial area of interest, and continuing interaction that have been necessary in previous approaches for moving between many spatial and abstract operations. We believe that perhaps the foremost value of our interface will be enabling users to easily perform tasks like loading and saving data, establishing video links, manipulating simulation parameters, and controlling presentations while their Implicit is the belief that the thread of engagement with 3D graphical visualizations and collaborators are generally the main objects of interest, and not secondary (albeit important) interface tasks. We believe our interface’s simple controls and physical legibility may be less cognitively de- manding than graphical interfaces (especially in the context of immersive environments), and could support VR use by a broader ranger of users. We hope that our visualization artifacts, used together in two-handed interaction with 3D pointing devices, will provide powerful tools for facilitating this balance between functionality and attentional cost. Our tangible interface is based upon three kinds of physical objects: pads, cards, and wheels. Interaction pads are modular elements used for operations like loading and saving data, establishing video links, manipulating simulation parameters, and controlling presentations. In their initial incarn- ation, they are embodied as a series of rectangular modules, each roughly the size of a VHS cassette. They include embedded RFID readers for sensing tagged physical tokens, and communicate with wired and wireless Ethernet. We are currently developing four core interaction pads: - the binding pad : for establishing and accessing data card bindings; - the placement pad : for spatially arranging data card contents on graphical displays; - the parameter pad : for binding and manipulating digital parameters using parameter wheels; and - the control pad : for navigating through media collections, streams, and temporal data (e.g., images, video, simulation time steps, etc.) Taken together, these pads will provide simple means for physically engaging with time, space, parameters, and information aggregates, which we believe will generalize over a variety of applications. These interaction pads are used together with data cards and parameter wheels . Data cards may be used to represent content such as data sets, simulation parameters, slide presentations, and live portals (e.g., video conference sessions). Parameter wheels will be bindable to different parameters, and used as kinds of reconfigurable “dial box” knobs to adjust and control simulation and visualization parameters. Figures 1 and 2 illustrate one prospective usage example. In addition to the pads, cards, and users, these images depict several other details. First, they illustrate an “Immersa- Desk” style large format stereo display where immersive visualizations are displayed. Secondly, the users wear stereo glasses and use a 3D tracker in one hand, while inter- acting with visualization artifacts with their second hand. As interactive use of wall displays is frequently conducted while sitting or standing immediately adjacent to the display, we have designed “furniture” in the form of an “interaction stand” for physically supporting and organizing the visualization artifacts. The stand also helps provide power and Ethernet connectivity to the interaction pads. We next consider the structure and function of our cards, wheels, and pads in more detail. “Data cards” – RFID-tagged cards with the size and feel of a credit card (Figure 3) – are the primary medium for repre- senting digital information within our system. These cards are each marked with six numbered, (optionally) labeled rows. Each of these rows can be associated with one or more elements of online (URL/URN-referenced) information. One or more of these rows can be selected with the binding pad as the active binding of the card “container”. This approach works to balance the benefits of physical embodiment and the legibility of visually labeled “con- tents,” while combating the flood of objects associated with traditional “one object, one binding” TUI approaches. Data cards are also color-coded and labeled with text (and perhaps visual icons) on their upper corner surfaces. This is intended to allow the cards to be rapidly sorted, and identified while held in a “hand” in a fashion similar to traditional playing cards [Parlett 1999]. The RFID tags within these cards each hold a unique serial number, as well as several hundred bytes of non-volatile RAM. The non-volatile RAM is used to hold the network address for a SQL database, which is used to hold the actual URLs and authentication information associated with data cards, as well as additional cryptographic information. Parameter wheels are an approach for expressing discrete and continuous parameters using small cylindrical “wheels” [Ullmer et al. 2003] (Figure 4). These wheels are used in fashions resembling the dials of dial boxes. In addition to the strengths of dial boxes, parameter wheels can be dynamically bound to different digital parameters. The physical/digital constraints within which parameter wheels are used may also be bound to different digital interpreta- tions, significantly increasing the expressive power of this approach. E.g., in Figure 4, the two left wheel constraints are bound to the “y” and “x” axes of a scatterplot visualization. By placing the wheel onto the right “x” constraint, the user both queries the database for the wheel’s parameter, and plots the results of this query along the scatter- plot’s “x” axis. Wheel rotation then allows manipulation of the wheels’ associated parameter values. Parameter wheels can be bound to desired parameters using special data cards. Manipulation of these wheels on the “parameter pad” can then be used to manipulate simulation parameters (e.g., time) as well as visualization parameters (e.g., “transparency”). Interaction pads represent specific digital operations. Their individual work surfaces contain RFID sensing regions, buttons, and displays for sensing and mediating interactions with data cards and parameter wheels. Each interaction pad has several shared features. Each has a work surface of roughly 16.5x10.5cm, and a depth of 4cm (this will be reduced in future iterations). Each also has four indicator LEDs, two of which have associated buttons (Figure 5). These include: - The target LED indicates that the interaction pad is “bound” to a specific visual display surface (e.g., an immersive wall or computer screen). By pressing the adjoining button, the target binding may be cleared. - The authorization LED indicates that the interaction pad has been securely authenticated with one or more users’ authentication credentials. Especially within collaboration contexts, this security mechanism plays an important role in (e.g.) allowing users to access ...