By Darren Waters
Technology editor, BBC News website
Footage courtesy of the Max Planck Institute for Biological Cybernetics
A stroll around the ancient city of Pompeii will be made possible this week thanks to an omni-directional treadmill developed by European researchers.
The treadmill is a "motion platform" which gives the impression of "natural walking" in any direction.
The platform, called CyberCarpet, is made up of several belts which form an endless plane along two axes.
Scientists have combined the platform with a tracking system and virtual reality software recreating Pompeii.
The key to the CyberCarpet is a platform with a large chain drive.
The chain drive is made up of 25 conventional treadmills which move in one direction, at right angles to the direction the chain is pulling.
The platform gives "walkers" a walking area of 4.5m by 4.5m and moves fast enough to allow jogging at about two metres per second.
Omni-directional treadmills are not new and have been in development for many years, including work done by the US military.
"This is the first omni-directional platform that allows near natural walking," said Dr Marc Ernst, research group leader at the Max Planck Institute for Biological Cybernetics, in Tubingen, Germany.
We are using virtual reality to study human behaviour.
Dr Marc Ernst
The belts and the chain work independently so the "walker" can be recentred on the platform if he were to accelerate from a point towards the edge of the platform.
The platform weighs 11 tonnes and a series of 40 kilowatt motors can move a mass of seven tonnes.
"The size of the platform matters," said Dr Ernst. "If you make it too small you have to counteract each step a person takes. It feels like walking on ice.
"You need some size and from a perceptual point of view the larger the better."
Dr Ernst said the platform would have to be 100m by 100m if a walker were to have no sensation of being recentred.
"To make it feel natural for walking you cannot go any smaller than six metres by six metres; it's a question of physics."
Dr Ernst said walking on the treadmill "feels great".
"It feels relatively natural. You do feel the acceleration of the belts.
"But you don't need any harness - we wear them for safety in case someone was to fall. But no-one ever has."
Scientists at the Max Planck Institute have combined the platform with virtual reality headsets to give the impression of walking or even running around 3D worlds.
The treadmill moves along two axes
The researchers have been working on a tracking system which lets "walkers" dispense with the type of suits used in Hollywood films for motion capture.
The system, which is part of a wider project called CyberWalk, uses cameras which track the position and posture of the individual.
That motion detection in turn controls the velocity of the treadmill and interactions with the virtual world.
The team is working with the Swiss Federal Institute of Technology (ETHZ), which has developed a software package for quickly creating large-scale virtual environments in particular cities, in various degrees of detail, called CityEngine.
At a conference in Tubingen this week the teams will show off CyberWalk and the CityEngine being used to let people stroll around ancient Pompeii and Rome.
"Pompeii is a great showcase because it lets you discover a city that no longer exists," said Dr Ernst.
He added: "We are using virtual reality to study human behaviour. We want to learn how different sensory signals are used by the human brain to generate representation or layout of a location.
"How do you create a mental layout of a town for the first time? We want to learn what information is used but also how you combine it.
"How do different sensory modalities interact?"
The teams believe the technology could be used in gaming, education, architecture and planning, disaster planning and training, as well as medical rehabilitation.
The platform is a result of a collaboration between the Swiss and German institutes, as well as the University of Rome, the Institute of Applied Mechanics and the Institute of Automatic Control Engineering, in Munich.
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