Software systems for modeling articulated figures

Research in computer animation and simulation of human task performance requires sophisticated geometric modeling and user interface tools. The software for a research environment should present the programmer with a powerful but flexible substrate of facilities for displaying and manipulating geometric objects, yet insure that future tools have a consistent and friendly user interface. Jack is a system which provides a flexible and extensible programmer and user interface for displaying and manipulating complex geometric figures, particularly human figures in a 3D working environment. It is a basic software framework for high-performance Silicon Graphics IRIS workstations for modeling and manipulating geometric objects in a general but powerful way. It provides a consistent and user-friendly interface across various applications in computer animation and simulation of human task performance. Currently, Jack provides input and control for applications including lighting specification and image rendering, anthropometric modeling, figure positioning, inverse kinematics, dynamic simulation, and keyframe animation

Principled Standard Setting Requires Consideration of More Than Science (AEI-Brookings Joint Center for Regulatory Studies, Brief 00-02) Brief Amicus Curiae in Support of Respondents, Browner v. American Trucking Associations, Inc., No. 99-1257, (U.S. September 11, 2000)(with 20 Law Professors, Economists, and Scientists)

Summary of Argument: Throughout this proceeding, EPA has identified no policy or normative criteria to justify its NAAQS standards, thus suggesting that science alone can be used to determine the appropriate air quality standard. Science plays a critical, indeed essential, role in evaluating the risks of possible air quality standards being considered for adoption by EPA. However, science by itself cannot provide the justification for selecting a particular air quality standard. Especially in setting standards for non-threshold pollutants, such as in this case, scientific evidence cannot alone indicate where the standard should be set, since any level above zero will cause some health effects. To provide a principled and consistent basis for justifying the setting of such standards at some level above zero, EPA must articulate other factors -- whether they be costs or other policy criteria -- to guide its decisions on where to set national ambient air quality standards

Identification of vortexes obstructing the dynamo mechanism in laboratory experiments

The magnetohydrodynamic dynamo effect explains the generation of self-sustained magnetic fields in electrically conducting flows, especially in geo- and astrophysical environments. Yet the details of this mechanism are still unknown, e.g., how and to which extent the geometry, the fluid topology, the forcing mechanism and the turbulence can have a negative effect on this process. We report on numerical simulations carried out in spherical geometry, analyzing the predicted velocity flow with the so-called Singular Value Decomposition, a powerful technique that allows us to precisely identify vortexes in the flow which would be difficult to characterize with conventional spectral methods. We then quantify the contribution of these vortexes to the growth rate of the magnetic energy in the system. We identify an axisymmetric vortex, whose rotational direction changes periodically in time, and whose dynamics are decoupled from those of the large scale background flow, is detrimental for the dynamo effect. A comparison with experiments is carried out, showing that similar dynamics were observed in cylindrical geometry. These previously unexpected eddies, which impede the dynamo effect, offer an explanation for the experimental difficulties in attaining a dynamo in spherical geometry.Comment: 25 pages, 12 figures, submitted to Physics of Fluid

Programming With Jack (Fourth Edition)

This manual describes the implementation of Jack™, with emphasis on how to extend it and modify it. The principle purpose of this manual is to describe what functions in the Jack libraries are available to be used in writing new features for Jack. The manual also gives an overview of how Jack works, for those interested in modifying its current behavior. This manual assumes that you already know how to use Jack, and are familiar with its basic terminology

Interactive Postural Control of Articulated Geometric Figures (Dissertation)

Interactive postural control is the process of interactively pushing, poking, and twisting parts of an articulated geometric figure for the express purpose of getting it into a desired posture. Many motion algorithms and computer animation techniques generate motion sequences based on starting and ending postures for geometric figures, but few of these techniques address the fundamental problem of specifying these postures. The goal of this thesis is to develop a system that allows us to specify postures of animate geometric figures in ways that suggest how we interact with real people. The emphasis of this thesis is on real-time interactive 3D manipulation. The elements of the interaction techniques form a powerful vocabulary for describing postures and postural adjustments. The vocabulary is not a spoken or written one; rather, it includes verbs acted out by the user through the movement of input devices. There are three major components to this work. The first component is a real-time 3D direct manipulation technique that allows the user to intuitively translate and rotate handles on objects using only a three button mouse as input. The second component is an inverse kinematics algorithm that uses the notion of constraints, or desired geometric relationships, to control postures of articulated figures. The inverse kinematics formulation is well suited to highly redundant figures. The final component is the system of behaviors. Behaviors provide coordination between the parts of the figure, so that when one part of a figure moves, the body reacts as a whole. One of the most important behaviors, and the one requiring the most coordination, is balance. The behaviors magnify the effect of the basic manipulation commands so that relatively few invocations of the commands are necessary to accomplish a complex positioning task

\u3cem\u3eJack\u3c/em\u3e 5 User\u27s Guide

This chapter is a brief tutorial introduction to using Jack. It demonstrates some of the basic Jack features, illustrating mostly the flavor of how you interact with Jack rather than describing the details of how to use it. The first time you run Jack, you should go through the examples in this chapter. From then on, refer to the later chapters for more details about the various features