virtual

This paper explores interfaces to virtual environments supporting multiple users. An interface to an environment allowing interaction with virtual artefacts is constructed, drawing on previous proposals for 'desktop' virtual environments. These include the use of Peripheral Lenses to support peripheral awareness in collaboration; and extending the ways in which users' actions are represented for each other. Through a qualitative analysis of a design task, the effect of the proposals is outlined. Observations indicate that, whilst these designs go some way to re-constructing physical co-presence in terms of awareness and interaction through the environment, some issues remain. Notably, peripheral distortion in supporting awareness may cause problematic interactions with and through the virtual world; and extended representations of actions may still allow problems in re-assembling the composition of others' actions. We discuss the potential for: designing representations for distorted peripheral perception; and explicitly displaying the course of action in object-focused interaction.

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 address http://uvacs.cs.virginia.edu/~kph2q/.

This paper describes a testbed and method for characterizing the dynamic response of the type of spatial displacement transducers commonly used in virtual environment (VE) applications. The testbed consists of a motorized rotary swing arm that imparts known displacement inputs to the VE sensor. The experimental method involves a series of tests in which the sensor is displaced back and forth at a number of controlled frequencies that span the bandwidth of volitional human movement. During the tests, actual swing arm angle and reported VE sensor displacements are collected and time stamped. Because of the time stamping technique, the response time of the sensor can be measured directly, independent of latencies in data transmission from the sensor unit and any processing by the interface applications running on the host computer. Analysis of these experimental results allows sensor time delay and gain characteristics to be determined as a function of input frequency. Results from tests of several differnt VE spatial sensors (Ascension, Logitech, and Polhemus) are presented here to demonstrate use of the testbed and method.

We describe a view-management component for interactive 3D user interfaces. By view management, we mean maintaining visual constraints on the projections of objects on the view plane, such as locating related objects near each other, or preventing objects from occluding each other. Our view-management component accomplishes this by modifying selected object properties, including position, size, and transparency, which are tagged to indicate their constraints. For example, some objects may have geometric properties that are determined entirely by a physical simulation and which cannot be modified, while other objects may be annotations whose position and size are flexible.We introduce algorithms that use upright rectangular extents to represent on the view plane a dynamic and efficient approximation of the occupied space containing the projections of visible portions of 3D objects, as well as the unoccupied space in which objects can be placed to avoid occlusion. Layout decisions from previous frames are taken into account to reduce visual discontinuities. We present augmented reality and virtual reality examples to which we have applied our approach, including a dynamically labeled and annotated environment.

We are developing an interaction technique for rich nonverbal communication through an avatar. By writing a single letter on a pen tablet device, a user can express their ideas or intentions, non-verbally, using their avatar body. Our system solves the difficult problem of controlling the movements of a highly articulated, 3D avatar model using a common input device within the context of an office environment. We believe that writing is a richly expressive and natural means for controlling expressive avatar gesture.

Many computer operating systems provide seamless support for multiple display screens, but there are few cross-platform tools for collaborative use of multiple computers in a shared display environment. Mighty Mouse is a novel groupware tool built on the public domain VNC protocol. It is tailored specifically for face-to-face collaboration where multiple heterogeneous computers (usually laptops) are viewed simultaneously (usually via projectors) by people working together on a variety of applications under various operating systems. Mighty Mouse uses only the remote input capability of VNC, but enhances this with various features to support flexible movement between the various platforms, "floor control" to facilitate smooth collaboration, and customization features to accommodate different user, platform, and application preferences in a relatively seamless manner. The design rationale arises from specific observations about how people collaborate in meetings, which allows certain simplifying assumptions to be made in the implementation.

This paper describes a Computer Aided Design system for sketching free-form polygonal surfaces such as terrains and other natural objects. The user manipulates two 3D position and orientation trackers with three buttons, one for each hand. Each hand has a distinct role to play, with the dominant hand being responsible for picking and manipulation, and the less-dominant hand being responsible for context setting of various kinds. The less-dominant hand holds the workpiece, sets which refinement level that can be picked by the dominant hand, and generally acts as a counterpoint to the dominant hand. In this paper, the architecture of the system is outlined, and a simple surface is shown.

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 address http://uvacs.cs.virginia.edu/~kph2q/.

We present the Haptic Shading Framework (HSF), a framework for procedurally defining haptic texture. HSF haptic texture shaders are short procedures allowing an application-programmer to easily define interesting haptic surface interaction and the parameters that control the surface properties. These shaders provide the illusion of surface characteristics by altering previously calculated forces from object collision in the haptic pipeline.HSF can be used in an existing haptic application with few modifications. The framework consists of user-programmable modules that are dynamically loaded. This framework and all user-defined procedures are written in C++, with a provided library of useful math and geometry functions. These functions are meant to mimic RenderMan functionality, creating a familiar shading environment. As we demonstrate, many procedural shading methods and algorithms can be directly adopted for haptic shading.

We have previously developed a collaborative infrastructure called SCAPE - an acronym for Stereoscopic Collaboration in Augmented and Projective Environments - that integrates the traditionally separate paradigms of virtual and augmented reality. In this paper, we extend SCAPE by formalizing its underlying mathematical framework and detailing three augmented Widgets constructed via this framework: CoCylinder, Magnifier, and CoCube. These devices promote intuitive ways of selecting, examining, and sharing synthetic objects, and retrieving associated documentary text. Finally we present a testbed application to showcase SCAPE's capabilities for interaction in large, augmented virtual environments.