Although the archive of text generated by a persistent conversation (i.e. newsgroup, mailing list, recorded chat, etc.) is searchable, it is not very expressive of the underlying social patterns. In this paper we will discuss the design of graphical interfaces that reveal the social structure of the conversation by visualizing patterns such as bursts of activity, the arrival of new members, or the evolution of conversational topics. Our focus is on two projects: Chat Circles, a graphical interface for synchronous conversation and Loom, a visualization of threaded discussion. Through these examples we will explore key issues in the generation, design and use of graphical interfaces for persistent conversations. 1.

This thesis describes a computer vision system for observing the "action units" of a face using video sequences as input. The visual observation (sensing) is achieved by using an optimal estimation optical flow method coupled with a geometric and a physical (muscle) model describing the facial structure. This modeling results in a time-varying spatial patterning of facial shape and a parametric representation of the independent muscle action groups responsible for the observed facial motions. These muscle action patterns are then used for analysis, interpretation, recognition, and synthesis of facial expressions. Thus, by interpreting facial motions within a physics-based optimal estimation framework, a new control model of facial movement is developed. The newly extracted action units (which we name "FACS+") are both physics and geometry-based, and extend the well known FACS parameters for facial expressions by adding temporal information and non-local spatial patterning of facial mot...

The goal of the proposed work is to develop a theory of design for building on-line social environments. The underlying hypothesis is that in order to foster the development of virtual communities and cultures, the environment must provide the means to communicate social cues and information: the participants must be able to perceive the patterns of activity and affiliation that reveal the structure of a community and to have a fluid and subtle vocabulary for conveying cultural information. The theoretical foundation for the research is drawn from traditional studies of society and culture and from observations of contemporary on-line systems. Starting with an analysis of the fundamental differences between real and virtual societies - most notably, the presence and absence of the body - the first section examines the ways social cues are communicated in the real world, discusses the limits imposed on online communities due to their mediated and bodiless nature, and explores directions...

This paper develops a highly automated approach to constructing realistic, working models of human heads for use in animation. These physics-based models are anatomically accurate and may be made to conform closely to specific individuals. We begin by scanning a person with a laser sensor which circles around the head, acquiring detailed range and reflectance information. Next, an automatic conformation algorithm adapts a triangulated face mesh of predetermined topological structure to these data. The generic mesh, which is reusable with different individuals, reduces the range data to an efficient, polygonal approximation of the facial geometry and supports a high-resolution texture mapping of the skin reflectivity. The conformed polygonal mesh forms the epidermal layer of a new, physics-based model of facial tissue. An automatic algorithm constructs the multilayer synthetic skin and estimates an underlying rigid "skull" substructure with a jointed jaw. Finally, the algorithm inserts synthetic muscles into the deepest layer of the facial tissue. These contractile actuators, which emulate the primary muscles of facial expression, generate forces that deform the synthetic tissue into meaningful expressions. To increase realism, we include constraints to emulate tissue incompressibility and to enable the tissue to slide over the skull substructure without penetrating into it. The resulting animate models appear significantly more realistic than our previous physics-based facial models. Keywords: Physics-Based Facial Modeling, Facial Animation, Cylindrical Facial Scanning, Feature-Based Facial Adaptation, Texture Mapping, Discrete Deformable Models. 1

Real-time finite element (FE) analysis can be used to represent complex deformable geometries in virtual environments. The need for accurate surgical simulation has spurred the development of many of the new real-time FE methodologies that enable haptic support and real-time deformation. These techniques are computationally intensive and it has proved a challenge to achieve the high modeling resolutions required to accurately represent complex anatomies. The authors present a new real-time methodology based on linear FE analysis that is appropriate for a wide range of surgical simulation applications. A methodology based is proposed that is characterized by high model resolution, low preprocessing time, unrestricted multi-point surface contact and adjustable boundary conditions. These features make the method ideal for modeling suturing, which is an element common to almost every surgical procedure. This paper describes constraints in the context of a Suturing Simulator currently being developed by the authors. I.

As computers are increasingly used to mediate social interaction, tools are needed not only to support direct communication, but also to create a richer social environment for the networked group. These include tools that provide information about the presence of others and that give the user a sense of the ongoing activities. This paper describes two ongoing research projects in this area. Collaboration-at-a-Glance is a visual interface to an electronic group. It creates an animated image of a remote meeting by compositing pictures of the participants so as to represent their actions. Visual Who is a window onto a larger community. Like a window onto a street, it shows the comings and goings of the community members. 1: Visualizing electronic presence William Whyte, describing what makes for a successful urban environment, said: “What attracts people most, in sum, is other people. If I labor the point, it is because many urban spaces are designed as though the opposite were true and as though what people liked best are the places they stay away from. “ Whyte went on to describe a number of places that attract people to them: they are places in which there are other people – sometimes familiar, often not. The key is the ongoing presence of others, of an environment that is vigorous and populated, one that has a constant flow of human activity. Whyte’s book is an argument against the design of spaces that do not draw people to them, against the bland corporate landscapes and the sterile plazas, against places that may perform their stated function efficiently, but that fail in their community role. The same principle – that the presence of other people is the key to a vital urban environment – is likely to hold true for electronic communities as well. Yet relatively little attention has been given to building the infrastructure to support this type of environment. Unlike the direct, taskoriented activities which are easy to describe (such as shared editing windows, or group calendars), the presence-

This thesis is about computer vision algorithms for the analysis of video data involving faces. This kind of video, obtained for example from a camera aimed to the user of some interactive system, is potentially useful to enhance the interface between users and machines. These image sequences provide information from which machines can identify and keep track of their users, recognize their facial expressions and gestures, and complement other forms of human-computer interfaces. First, we present a learning technique based on information-theoretic discrimination which is used to construct face and facial feature detectors. Next, we describe a real-time system for face and facial feature detection and tracking in continuous video. Last, we present a probabilistic framework for embedded face and facial expression recognition from image sequences. The aforementioned learning technique, referred to in this thesis as information-based maximum discrimination, uses the information-theoreti...

ix Chapter 1. Quantum Field Theory: No Gauge Group 1 1.1

Petajan, Dimitri Terzopoulos, and Keith Waters for putting together the main sections of this report, and to Ken Shoemake for contributing the summary. We appreciate the time and text (and video) all the Workshop participants contributed to make this report possible. We would like also to thank Dawn Becket for helping edit early drafts of this report. Finally, we would like to give our most special thanks to Elaine Benedetto for her kindness and help in organizing the myriad details of this Workshop.