"A Spacially Immersive Display and 3D Video Portal for Telepresence". With this – for outsiders, somewhat intimidating – description, people working on the blue-c project (1) greeted visitors to their Demo Day last week. At the two centres where blue-c is stationed, on the campus Hönggerberg and in the computer centre in Clausiusstrasse, visitors were informed about what lies hidden behind this seemingly meaningless string of words. Those among them who let themselves be abducted by the researchers found themselves in a virtual world and encountered blue-c as a fascinating and highly complex technology, albeit one that leaves room for improvement.

Ambitious project

The development of a new technology for virtual 3D communication is probably one of the most ambitious projects ever undertaken at ETH Zurich. In all, working groups from four departments are involved in the blue-c project. The goal, shared by all groups, is seductive: people standing in different places should be able to communicate with one another in real time, not only by hearing and seeing one another but by actually perceiving each other as three-dimensional beings in seemingly real surroundings. It is quite possible, thanks to blue-c, that an architect in Zurich can visit, together with his colleague in Los Angeles, a planned construction in Tokyo – without either of them having to set foot on plane or a boat.

Naturally, this can only be achieved with a highly contingent and wide array of technical arrangements. In order that the partners can really communicate in real time images must be taken and projected in a parallel mode. This calls for extremely sophisticated technology, especially in the station in the computer centre. The images to be transmitted are projected on to three walls in the station. To prevent the surroundings of the illustrated virtual world from being unnecessarily disturbed with the real equipment, the cameras taking the pictures of the subject in the station are installed behind the walls. This raises a basic dilemma: to project the images the room should be darkened, but light is needed to take the pictures.

Glass that can be turned on and off

Researchers working on blue-c have resolved this catch-22 with a refined – not to say cunning – technique. The walls of the station are made of glass panels that can be turned on and off at a speed of 60 times per second, which means they are then either transparent or opaque. When opaque the image of the partner in the other station is projected on to the wall, together with his virtual surroundings. When the walls are transparent, the station is illuminated with approximately 10,000 light emitting diodes and the person standing in the station is filmed without noticing a thing.

blue-c demonstrates how, in future, people will be able to meet and communicate in virtual space. The representation of the partner, however, sometimes leaves room for improvement. large

A visitor in the "red hell" on the campus Hönggerberg plays chess with a partner in the ETH computer centre. Both players can freely "move" over the board and communicate directly with one another. large

From the pictures taken by the total of sixteen cameras, and with the help of very canny algorithms, the computer creates a so-called point cloud, which represents the surface of the body of the person represented in the pictures. This data is transmitted to a second station where the person in the first station is projected as a three-dimensional being. The biggest difficulty of the process is that the time accorded to carry out these calculations is very short. After all, the goal is to transmit the pictures as nearly simultaneously as possible.

Asymmetric architecture

The station at the campus Hönggerberg is somewhat simpler. The projection that arrives in the "red hell", while three-dimensional, is projected on to a single wall. This means that the pictures and the projection are easier to synchronise here. The asymmetric architecture of blue-c was especially chosen with this solution in mind. For one thing, it was impossible, for financial reasons alone, to build such a complex station as that in the computer centre. But the researchers also wanted to install a station that would be open to the public.

The actual demonstrations show that it will still be some time before blue-c becomes part of everyday experience. The navigation in three-dimensional space alone calls for a high measure of dexterity on the part of the participants. It must also be said that the quality of the projection of the person "on the other side" leaves much to be desired. The system is very sensitive to such disturbances as onlookers standing around the station. In addition, some garments, such as dark trousers, are simply not projected into the partner station. And when more than one person stands in the same station the computer can hardly cope with the flood of data it receives. With the complex technology used in the Centre it would not be possible to accomplish this.

Still at the infant stage

The area of image processing in particular is an important focus point for the follow-up project called blue-c-II (2). The technology, the researchers explain, is still in its infancy and can be compared to the first flickering pictures on television screens. They are confident that great progress will be made in coming years. For example, they want to be able to project the real surroundings, too, of the person being sent into virtual space. The aim is to be able to project not just single objects, but entire rooms. Then, the goal of being able to meet in a location-independent virtual space and in real-time space would be a lot nearer.