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Technique brings virtual reality closer to physical reality

Researchers at MIT's Rapid Autonomous Machining Laboratory have developed a procedure that enables a human user to touch virtual environments with full three-dimensional realism. The advance brings the promise of virtual reality one step closer to fully representing the intricate aspects of the physical world.

The researchers, collaborating with engineers at Suzuki Motor Corp., are adapting the system to computer-aided design and manufacturing applications. The MIT software, combined with a haptic device developed by engineers at Suzuki, creates a virtual world of touch with an added dimension that had not been possible before. Just as the mouse has revolutionized our interaction with computers, this new technology is expected to enhance and widen the field of virtual reality. MIT and Suzuki plan to offer the new technology as an integrated development environment for third-party use.

Computer screens provide a visual display to stimulate the sense of sight; a haptic interface influences a user through the sense of touch. Professor Sanjay Sarma and his research associates have developed a method that allows haptic systems to work with arbitrary 3-D probes, not just a point.

"What we hope to contribute is an innovation that we and others can use to make these simulations more realistic," he said. "Approximating the probe of a haptic interface as a point is computa-tionally easier. But the full geometry of the tool is ignored and much of the realism is lost with it. Our methodology enables full three-dimensional modeling in haptic environments."

At the advent of haptic interfaces, the user's presence in the virtual world was restricted to control of a single point with which he or she could poke at the objects in the virtual environment. Even with a single point, the user was able to touch and feel a variety of surfaces.

The new invention extends the capabilities of haptic interfaces by simulating the interaction between fully three-dimensional bodies within the virtual environment. As a result, the user's presence is no longer restricted to control of a single point; any three-dimensional solid could be used to probe the virtual environment.

Researchers all over the world are investigating haptic applications that achieve a variety of tasks, from computer-aided design to surgical simulation and training. In these systems, the user is in control of a tool that acts upon the virtual environment. In the past, these tools were represented as a single point when in reality they are three-dimensional solids.

The technology hinges on a new rapid interference analysis procedure developed at MIT. The requirements of haptic systems are stringent. Developments in haptics must use clever procedures to make the best use of the fastest processors available.

Stephen Ho, the graduate student developing the new procedure, compares the progress of haptic interfaces to computer graphics. "We see in computer graphics an evolution towards realism. Haptics will follow the same path," he said.

"Computer graphics have benefited from advancements in rendering techniques and computer processing power. Haptic development will rely on increased processing power as well as advancements in technique like this invention."

Added Professor Sarma, "Fully realistic touchable environments are in our future, and this innovation in haptic approach brings us closer."

"As mechanical engineers, our interest in haptic interfaces grew from manufacturing applications," he said. The first application of the new technology is for a haptic system that creates machining tool paths for rapid prototyping. The user manipulates a cutting tool in virtual space to "teach" the machine how to cut a specified object.

The machine tool path application requires the complexity of full-body haptics, since machine tool geometry must be accurately modeled in the simulation to capture the geometric interaction between the cutting tool and the target creation. While the new procedure was created for a computer-aided design and manufacturing application, "The realization of full-body haptic interaction will have a significant role in other haptic applications as well," Professor Sarma said.

A version of this article appeared in the April 28, 1999 issue of MIT Tech Talk (Volume 43, Number 28).

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