Balloon Selection is a 3D interaction technique that is modeled after the real world metaphor of manipulating a helium balloon attached to a string. Balloon Selection allows for precise 3D selection in the volume above a tabletop surface by using multiple fingers on a multi-touch-sensitive surface. The 3DOF selection tasks is decomposed in part into a 2DOF positioning task performed by one finger on the tabletop in an absolute 2D Cartesian coordinate system and a 1DOF positioning task performed by another finger on the tabletop in a relative 2D polar coordinate system. We have evaluated Balloon Selection in a formal user study that compared it to two well-known interaction techniques for selecting a static 3D target: a 3DOF tracked wand and keyboard cursor keys. We found that Balloon Selection was significantly faster than using cursor keys and had a significantly lower error rate than the wand. The lower error rate appeared to result from the user's hands being supported by the tabletop surface, resulting in significantly reduced hand tremor and arm fatigue. Keywords: 3D interaction, selection technique, augmented reality, virtual reality, world-in-miniature, multi-touch interaction, cross-dimensional interaction, hybrid user interface.  In their survey paper, Hinckley et al. [23] identify many of the challenges associated with designing 3D interactions, dividing the design space into two broad categories: those that deal with human perception and those that deal with ergonomics. The authors suggest that spatial references (props or the user's own body), two-handed interaction, multi-sensory feedback, and physical constraints are invaluable for helping users to perceive and interact with a 3D object and environment. They also strongly recommend the reduction of extraneous degrees-of-freedom (DOF) to simplify the 3D task when possible. For example, in tasks requiring translation, but not rotation, rotation should be disabled. Furthermore, they suggest that providing a clear control metaphor (e.g., eyeball-in-hand [2, 9] camera or ray-casting) significantly improves the effectiveness of the interface and enhances the ability of the user to perceive the task at hand. In this paper, we present a novel interaction technique, called Balloon Selection (Figure 1 ), which follows these guidelines and allows for precise and accurate 3D selections in a constrained within-reach 3D environment. We are particularly interested in scenarios in which the user wishes to interact with a very small scale 3D environment, such as a model of the city, university campus, or an archaeological dig site [4, 25] , seen from an outside-in (exocentric) view. Such environments, also known as 3D maps or world-in-miniature (WIM) models [37] , are particularly well suited for collaborative scenarios in which multiple users discuss and analyze a given model over an augmented tabletop (e.g., [4, 35] ). Unfortunately, objects in small scale WIMs tend to be very hard to select, due to their small size, closeness, and potential overlap (Figure 2) . We designed Balloon Selection to fully exploit the benefits of a firm touch-sensitive surface to assist the user in accurate 3D selections. First, the surface is able to provide passive haptic support for the user's hands, which would otherwise need to be held continuously in mid air. By having the user rest their hands on the surface, we improved selection accuracy by significantly reducing hand tremor and arm fatigue. Second, when the user's hands are on the surface, they tend to remain below the 3D model and thus do not obscure the 3D objects being manipulated. Third, we took advantage of the multi-touch surface by designing a technique that decomposes the 3DOF selection task into a 2DOF positioning task performed by one finger on the tabletop in an absolute 2D Cartesian coordinate system and a 1DOF positioning task performed by another finger on the tabletop in a relative 2D polar coordinate system. * e-mail: benko@cs.columbia.edu † e-mail: feiner@cs.columbia.edu Figure 1 : Balloon Selection in action. 3D spherical cursor above the surface is controlled by multi-finger interaction on the touchsensitive surface. This image is taken through a video-mixed augmented reality system on a black paper-covered projection surface.
To allow interactions in the 3D space Benko et al. REF introduced the Balloon Selection, a 3D interaction technique that is modelled after the real-world metaphor of manipulating a helium balloon attached to a string.
Balloon Selection: A Multi-Finger Technique for Accurate Low-Fatigue 3D Selection
2007 IEEE Symposium on 3D User Interfaces
2007 IEEE Symposium on 3D User Interfaces
Computer Science