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Overview - Computer Animation and Virtual Environments

Most of my recent work has been in the area of virtual environments, although historically I have had interest in both computer animation (see projects) and virtual environments (see projects). In computer animation, I develop methods that allow the creation of visually compelling human motion. I am especially interested in the evaluation of such methods, and how such evaluation informs the design process. Evaluation techniques for animation contain a strong perceptual component, which closely links with my related research interest, that is, how people perceive and act on their perceptions in virtual environments. I am particularly interested in the construction of virtual environments that leverage perceptual affordances. Outside of these, I am also interested in a variety of other interesting research.

Computer Animation

Background. The most fundamental issue in using animation in a learning system is the problem of authoring the animation. Authoring visually compelling animation is a difficult and time-consuming task. People are able to perceive subtle movements and attribute style, emotion, and intent to these movements, and thus the bar for quality animation is high. Most animation techniques are ad hoc and employ heuristic techniques to achieve acceptable results. Authoring methods for animation can be broadly classified into three categories: motion capture, dynamic simulation, and keyframing. Motion capture is a popular process for generating human animation, in which sensors are attached to a performer and the motion of the performer is recorded for later playback in a graphical character. Dynamic simulation uses the physics of the graphical character to constrain the motion to be physically correct. Keyframing is the traditional Disney-like type of animation. My research has made contributions for all three of these techniques.

Specific projects:

Motion Transitions
Much computer animation is generated by concatenating clips of motion together. Vital to the success of this method is the proper generation of motion transitions, segues between the motion segments. For reasons of computational efficiency, linear transitions between segments are often used. This work has explored methods of constructing transitions, and psychophysics of how transitions are perceived.
Reusing Traditional Animation
This work explores the computer-assisted creation of novel cartoon animation. Sometimes, the realism of motion capture or dynamic simulation is not wanted. One can imagine learning environments, particularly for children, in which traditionally animated characters with caricatured or non-human features serve as a better representation for an agent. Authoring, editing, and re-using traditional animation are some of the most difficult and time-consuming animation tasks.
Motion Capture
Our work developed methods to insure that the recording process is done as faithfully as possible. This collaborative work unlocked motion capture data for use in synthesis algorithms by developing techniques to robustly estimate skeleton size and process similar motions into compatible sets. These results led to methods for controllable synthesis of stylistically similar but novel motions.
Variability in dynamic simulations
Building active dynamic simulations that produce visually compelling motion is fundamentally one of control design. Animation generated by dynamic simulation is sometimes criticized as appearing ``robotic,'' and part of the reason for this criticism can be traced to a lack of variability in the motion, i.e., a repetitive motion is a boring motion. This work adds variability to the control structure in ways that result in stable, yet pleasing motion.

Virtual Environments

Background My interest in virtual environments (VEs) is to study them as learning environments. As such, my work explores higher level design issues associated with learning environments. My work can be categorized into desktop learning systems and immersive virtual environments. The important point of this work is to build systems that allow people to learn in meaningful contexts and situations. For immersive virtual environments, my research develops design principles for immersion that allow environments where people can actively explore and guide their own learning. For desktop environments, my work has focused on the incorporation of compelling animation into a learning system, called the teachable agent system.

Specific Projects:

Spatial reasoning and locomotion in HMD-based virtual environments
A significant problem for HMD-based virtual environments that are large and that enable people to actively explore them will then be the problem of space. Having large areas suitable for active exploration of a large virtual environment is often not practical. This work addresses issues of learning in virtual environments and how subjects can explore large environments on foot when physical space is constrained.
Pedestrian Safety
We investigate how people perceive approaching traffic in virtual environments. The goal of this study is to improve pedestrian traffic crossings. This work is important since there were over 4500 pedestrian fatalities in 2003 in the United States.
Animated Learning Environments
This work examines the means and utility of using animated agents to promote positive learning experiences. The particular target audience is K-12 students. The paradigm and platform that we explore animated under are teachable agents.

Other Projects

Background I have been privileged to work with colleagues both from Vanderbilt University and nationally. Some of the projects we've worked on are listed here.

Computational Photography - Relighting
Lighting has long been recognized as a difficult problem in the field of computer graphics. We apply simplified image-based lighting methods to reduce the equipment, cost, time, and specialized skills required for high-quality photographic lighting of desktop-sized static objects such as museum artifacts.
Learning and Generation of Robotic Behaviors
The relationship between humanoid robotics and human-figure animation is synergistic, as each discipline provides tools and techniques of use to the other. Viewing robots as primitive learners, our results show that a robot can learn to interact purposefully with its environment through a developmental acquisition of sensory-motor coordination.
Visualization of Computational Models of Cognition
Computational models of cognition often exhibit rich complex dynamics that are difficult to discern without the use of visualization tools. We developed NAV, the Node Activity Visualizer, to remedy these deficiencies. NAV provides a sketch-based interface for constructing a graphical neural model and to display node activation levels, and can generate animations of simulation results.
3-D Visualization of Proteomic Information
This work developed methods to pre-process and visualize matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI IMS) data aligned with optically determinable tissue structures in three dimensions.
Transmission of Meshes over Lossy Channels
The continual improvement in computer performance together with the prevalence of high-speed network connections with high throughput and moderate latencies enables the deployment of multimedia applications, such as collaborative virtual environments, over wide area networks. We modified the progressive meshes for use in two transmission schemes, a hybrid transmission that uses TCP and UDP to send packets and a forward error-correcting transmission scheme that uses redundancy to decode the information sent.

Graduate work in Automatic Control

While a graduate student at Caltech, I worked on control techniques for a thrust-vectored ducted fan engine, a system built and maintained there. The ducted fan is an interesting example because it's unstable and nonlinear. You can find out more about it by going the Ducted Fan Project Page. Note that I worked on the ``old'' ducted fan; the new one is less nonlinear and much nicer.


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Bobby Bodenheimer