Sewing Worlds Together With SEAMS A Mechanism for Constructing Large-Scale Virtual Environments Project duration: 1997 Contact: Gernot Schaufler, Dieter Schmalstieg
Description	A SEAM (Spatially Extended Anchor Mechanism) is a new paradigm to connect virtual environments. It can best be described as a "door to another world".
Application	Large scale virtual environments can be arranged and assembled in a comprehensive and organized way, even if many uncoordinated designers have to cooperate.
Problems	Virtual environments on the Internet are usually based upon the popular VRML standard and use a teleportation metaphor (WWWAnchor) to travel from one world to the next. This does not make use of spatial coherence and frequently leads to disorientation.
Approach	We propose a new mechanism for connecting virtual worlds called SEAM (Spatially Extended Anchor Mechanism) that does not suffer from the mentioned shortcomings. It can best be described as a door into another world. Technically, a SEAM is a polygon through which a live image of another world is visible. A SEAM is defined by a single polygon at arbitrary position. Users can gaze through the SEAM into another world, but they may also walk through it (see pictures) or reach through it to manipulate another world.
Publication	(zipped) Sewing Worlds Together With SEAMS: A Mechanism To Construct Complex Virtual Environments : D. Schmalstieg, G. Schaufler

The pictures below show a user's avatar before and after traveling a SEAM:

Applications

A large variety of exciting applications is made possible by SEAMS:

• a global, continuous 3-D information space that is simple to manage and scaleable
• distributed architectural walkthroughs and other visual simulations
• a new user interface tool for positioning and manipulating arbitrary 3-D applications

SEAMS in polular media

SEAMS are quite common in books, movies and TV shows. This is the reason why the concept is easily understood by unexperienced users and turn out to be an excellent navigation metaphor. Here are some examples.

Sample images

Going through a billboard into a fascinating city:

A SEAM can also be used to create a mirror:

An interesting effect is infinite recursion, like a mirror mirrored in a mirror:

We have also tried out to use SEAMS as a 3-D user interface tool for Augmented Reality. The user wears a see-through head-mounted display and can see his surrounding and also windows into 3-D applications that can be positioned and manipulated using a pen-like 3-D input device.

With Augmented Reality, SEAMS are very useful for medical examinations by giving the viewer X-Ray lenses:

Moving pictures...

say more than words:

The TVWORLD movie shows a live recording of navigating through two worlds that are connected by TV sets that function as portals. Note that normal geometry does not allow to go from the living room to TV land and back in that fashion!

• Uncompressed QuickTime (2.4M)

• Zipped QuickTime (1.8M)

• Uncompressed QuickTime (1.3M)

• Zipped QuickTime (400K)