Technical Reports (CIS)

Document Type

Technical Report

Date of this Version

October 1991


University of Pennsylvania Department of Computer and Information Science Technical Report No. MS-CIS-91-82.


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.



Date Posted: 16 August 2007