How does it work ?

The installation establishes a full duplex communication between the two worlds.
Second Life is simply projected on a large screen and uses an in-game fixed camera to override the default third-person view.

To get our real world projected inside SL, we use a feature implemented by Linden Labs that allows parcel owners to replace a certain texture by a Quicktime video stream. It's the only way to display a video in Second Life, most of the time, pre-recorded ones. The idea here is to use a live stream of the real place instead.



Very basically, the installation needs a large projection screen, and in front of it, a zone on the ground from which the people will be seen by the camera.
Practically, the setting is adapted according to the physical place. The iMAL exhibition space is structured by concrete columns, seperated by 4 meters. Those columns was an easily recognizable element that we could duplicated in Second Life to intensify the mirroring feeling between the two worlds.

The screen was pulled out somewhere between two columns, from ground to ceiling - as a large gate, and the visibility/interaction zone was defined by a black carpet layed down between 4 columns in front of the screen.
So the installation was 8 meters long, 4 meters large, and almost 4 meters high. To which you must add the projector, hung to the ceiling, around 3 meters behind the projection screen.

For The Gate at iMAL, we build our own projection screen with white Lycra stretched between two aluminium tubes.

Hardware needed

- a digital projector, powerful enough to project through the screen (from behind it).
- a small firewire camera with a relatively large angle lens. We need large angle to be able to film the whole "zone" while keeping it as close as possible to the projection screen.
- a computer linked to the camera to compress the video and send it to a quicktime streaming server (we used an iMac G5 with the Quicktime Broadcaster ; it is possible to do it a Windows PC, but there is no free broadcaster software)
- a solid Quicktime/Darwin streaming server, able to stream the video to every visitor of The Gate in Second Life (it can go up to 60-70 clients at the same time)
- a second computer, connected as a client to Second Life, to provide the view projected on the screen. A graphic card with solid 3D abilities is recommended (also see the system recommendations on Second Life official website : )
- two loudspeakers

To be safe, we used two broadband internet connections for the installation. One was only used by the Second Life client, when the other was uploading the video stream to the streaming server (provided by This should, however, be able to work with a single connection with a decent upload bandwidth.

In Second Life

A terrain parcel is needed for the SL part of the installation. We need to be allowed to build and set a video stream for the parcel. In Second Life, it means that you either have to be the owner, sub-rent it, or have it lent.
In our case, the Odyssey Project lent us a space for the 4 days of the exhibition.
In terms of size, the SL space will need to be twice the size of the real space, simply because at a 1:1 scale it will look much smaller than it actually is.