Two-handed virtual manipulation

We discuss a two-handed user interface designed to support three-dimensional neurosurgical visualization. By itself, this system is a “point design, ” an example of an advanced user interface technique. In this work, we argue that in order to understand why interaction techniques do or do not work, and to suggest possibilities for new techniques, it is important to move beyond point design and to introduce careful scientific measurement of human behavioral principles. In particular, we argue that the common-sense viewpoint that “two hands save time by working in parallel ” may not always be an effective way to think about two-handed interface design because the hands do not necessarily work in parallel (there is a structure to two-handed manipulation) and because two hands do more than just save time over one hand (two hands provide the user with more information and can structure how the user thinks about a task). To support these claims, we present an interface design developed in collaboration with neurosurgeons which has undergone extensive informal usability testing, as well as a pair of formal experimental studies which investigate behavioral aspects of two-handed virtual object manipulation. Our hope is that this discussion will help others to apply the lessons learned in our neurosurgery application to future two-handed user interfac

A survey of design issues in spatial input

We present a survey of design issues for developing effective free-space three-dimensional (3D) user interfaces. Our survey is based upon previous work in 3D interaction, our experience in developing free-space interfaces, and our informal observations of test users. We illustrate our design issues using examples drawn from instances of 3D interfaces. For example, our first issue suggests that users have difficulty understanding three-dimensional space. We offer a set of strategies which may help users to better perceive a 3D virtual environment, including the use of spatial references, relative gesture, two-handed interaction, multisensory feedback, physical constraints, and head tracking. We describe interfaces which employ these strategies. Our major contribution is the synthesis of many scattered results, observations, and examples into a common framework. This framework should serve as a guide to researchers or systems builders who may not be familiar with design issues in spatial input. Where appropriate, we also try to identify areas in free-space 3D interaction which we see as likely candidates for additional research. An extended and annotated version of the references list for this paper is available on-line through mosaic at addres

New Applications for the Touchscreen in 2D and 3D Medical Imaging Workstations

We present a new interface technique which augments a 3D user interface based on the physical manipulation of tools, or props, with a touchscreen. This hybrid interface intuitively and seamlessly combines 3D input with more traditional 2D input in the same user interface. Example 2D interface tasks of interest include selecting patient images from a database, browsing through axial, coronal, and sagittal image slices, or adjusting image center and window parameters. Note the facility with which a touchscreen can be used: the surgeon can move in 3D using the props, and then, without having to put the props down, the surgeon can reach out and touch the screen to perform 2D tasks. Based on previous work by Sears, we provide touchscreen users with visual feedback in the form of a small cursor which appears above the finger, allowing targets much smaller than the finger itself to be selected. Based on our informal user observations to date, this touchscreen stabilization algorithm allows ta..

Passive Real-World Interface Props for Neurosurgical Visualization

We claim that physical manipulation of familiar real-world objects in the user's real environment is an important technique for the design of three-dimensional user interfaces. These real-world passive interface props are manipulated by the user to specify spatial relationships between interface objects. By unobtrusively embedding free-space position and orientation trackers within the props, we enable the computer to passively observe a natural user dialog in the real world, rather than forcing the user to engage in a contrived dialog in the computer-generated world. We present neurosurgical planning as a driving application and demonstrate the utility of a head viewing prop, a cutting -plane selection prop, and a trajectory selection prop in this domain. Using passive props in this interface exploits the surgeon's existing skills, provides direct action-task correspondence, eliminates explicit modes for separate tools, facilitates natural two-handed interaction, and provides tactile ..

I!!la HumanFactors inComputing Systems Passive Real-World Interface Props for

We claim that physical manipulation of familiar real-world objects in the user’s real environment is an important technique for the design of three-dimensional user interfaces. These real-world passive inte~ace props are manipulated by the user to specify spatial relationships between interface objects. By unobtrusively embedding free-space position and orientation trackers within the props, we enable the computer to passively observe a natural user dialog in the real world, rather than forcing the user to engage in a contrived dialog in the computer-generated world. We present neurosurgical planning as a driving application and demonstrate the utility of a head viewing prop, a cutting-plane selection prop, and a trajectory selection prop in this domain. Using passive props in this interface exploits the surgeon’s existing skills, provides direct action-task correspondence, eliminates explicit modes for separate tools, facilitates natural two-handed interaction, and provides tactile and kinesthetic feedback for the user. Our informal evaluation sessions have shown that with a cursory introduction, neurosurgeons who have never seenthe interface can understand and use it without training. KEYWORDS three-dimensional interaction, gesture input, two-hande