The Fishtank Illusion is a basic augmented environment designed both as a tutorial and an example of what an Augmented Environment is, and what an Illusion looks and feels like. Bear in mind that Fishtank is a very simple example, but it should give you an idea of what you can achieve.


To run Fishtank all you need is the installer, which you should run to install the Fishtank application. This is compiled to run on Windows 2000 / XP only and the DirectX runtime files must be installed. However, for video input you’ll need some DirectShow video device (such as a webcam with appropriate driver). For a full augmented environment you’ll also need a projector, otherwise you’ll see the Illusion on-screen only.

Assuming you have a camera and projector, turn on the projector and ensure that the camera is positioned such that it has a view of the entire projection. The further from the axis of projection the camera is the less accurate the augmentation will be. Set your graphics card up to put the primary output to the projector.

Operating the Illusion

With the camera and projector set up, run Fishtank. OpenIllusionist will automatically detect all the video inputs that are currently available and populate the dropdown list with them. Select the camera which is pointed at the projection. When you click “Launch”, the Illusion will begin, though it will not be correctly calibrated. Press F9 and Fishtank will attempt to calibrate for both perspective distortion and ambient lighting conditions. To make this process as easy as possible, make sure a dark object is present in front of the projection and in view of the camera. The Illusionist will project a series of circles to estabish the geometric relationship between camera and projection. This section of the calibration should be very fast; if you experience difficulty at this stage post on our forum with a description of the problem. One thing to try is varying the lighting conditions; depending upon the quality of camera and projector you’re using, very bright and very dark conditions can cause difficulties.


  • F9 – Recalibrate / Cancel calibration process
  • F11 – Show / hide “Sensors” – the feedback points that the agents use to see the world can be rendered or hidden. This has no effect on the behaviour of the agents.
  • Enter – Show / hide “Walls” – The Illusion operates on an edge detected, simplified version of the live video feed. Rendering the walls will allow you to see what the Illusionist sees and what it is possible for the agents to detect on their sensors. Rendering the walls is a processor intensive option, and will slow the response time of the Illusion. If you have no projector or cannot calibrate the system, rendering the walls allows you to get a feel for the Illusion on-screen.
  • F1 – Spawn “Fish” agent – the fish simply swims around and will try to swim around any objects it encounters
  • F2 – Spawn “Starfish” agent – the starfish will do nothing unless prodded by an object, when it will be pushed out of the way.
  • F8 – Remove the newest agent from the Illusion
  • Esc – Drop out to the input selection dialog. Close this to end the illusion, or re-launch to continue playing. Note that the illusion is suspended not destroyed when you drop out to the input selection box – if you re-launch, it will continue from the point that you dropped out.