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Virtual Humans

Only fifty years ago, computers were barely able to compute useful mathematical functions. Twenty-five years ago, enthusiastic computer researchers were predicting that all sorts of human tasks from game-playing to automatic robots that travel and communicate with us would be in our future. Today's truth lies somewhere in-between. We have balanced our expectations of complete machine autonomy with a more rational view that machines should assist people to accomplish meaningful, difficult, and often enormously complex tasks. When those tasks involve human interaction with the physical world, computational representations of the human body can be used to escape the constraints of presence, safety, and even physicality.

Virtual humans are computer models of people that can be used

Recent improvements in computation speed and control methods have allowed the portrayal of 3D humans suitable for interactive and real-time applications. There are many reasons to design specialized human models that individually optimize character, performance, intelligence, and so on. Many research and development efforts concentrate on one or two of these criteria.

In the efforts that we describe here, we cross several domains which in turn build from various interrelated facets of human beings (Fig. 1):

From these virtual humans research areas, many current, emergent, or future major applications are enabled:

Besides general industry-driven improvements in the underlying computer and graphical display technologies themselves, virtual humans will enable quantum leaps in applications requiring personal and live participation.

Figure 1: Virtual human applications, technology, and science.

In building models of virtual humans, there are varying notions of virtual fidelity. Understandably, these are application dependent. For example, fidelity to human size, capabilities, and joint and strength limits are essential to some applications such as design evaluation; whereas in games, training, and military simulations, temporal fidelity (real-time behavior) is essential. In our efforts we have attacked both.

Understanding that different applications require different sorts of virtual fidelity leads to the question of what makes a virtual human ``right''?

Unfortunately the state of research in virtual humans is not as advanced as to make the proper selection a matter of buying off-the-shelf systems. There are gradations of fidelity in the models: some models are very advanced in a narrow area but lack other desirable features.

In a very general way, we can characterize the state of virtual human modeling along at least five dimensions:

The arrows and hash marks are meant to be qualitative indicators of where we think usable technology exists today. Understanding that the arrows can actually extend an undetermined distance to the right, the idea is nonetheless being conveyed that we (and others) have proceeded rather far beyond the individual rendering of still frames as realized by traditional hand animation or even computer assisted cartoon animation. If we need to invoke them, the appearance of increasingly accurate physiologically- and biomechically-grounded human models may be obtained. We can create virtual humans with functional limitations that go beyond cartoons into instantiations of known human factors data. Animated virtual humans can be created in human time scales through motion capture or computer synthesis. Virtual humans are also beginning to exhibit the early stages of automony and intelligence as they react and make decisions in novel, changing environments rather than being forced into fixed movements. Finally, rather preliminary investigations are underway to create characters with individuality and personality who react to and interact with other real or virtual people [21,22,9,29,34,40].

The University of Pennsylvania has been very actively engaged in research and development of human-like simulated figures. Our interest in human simulation is not unique, but the complex of activities surrounding our approach is. The framework for our research is a software system called Jack [3]. Jack is an interactive system for definition, manipulation, animation, and performance analysis of virtual human figures. Our philosophy has led to a particular realization of a virtual human model that pushes the above five dimensions toward the right:

Virtual humans are different than simplified cartoon and game characters. What are the characteristics of this difference and why are virtual humans more difficult to construct? After all, anyone who goes to the movies can see marvelous synthetic characters (aliens, toys, dinosaurs, etc.), but they have been created typically for one scene or one movie and are not meant to be re-used (except possibly by the animator -- and certainly not by the viewer). The difference lies in the interactivity and autonomy of virtual humans. What makes a virtual human human is not just a well-executed exterior design but movements, reactions, and decision-making which appear ``natural,'' appropriate, and contextually-sensitive.

next up previous
Next: Agents and Avatars Up: Virtual Humans for Animation Previous: Virtual Humans for Animation

Dr. Norman Badler
Thu Apr 17 08:17:25 EDT 1997