Extended tracking enables you to keep tracking triggers at further distances and greater angles than you would be able to normally. It can even track when the features of the trigger image are no longer visible.
The trade-off is that you have less certainty that the tracking will be fully accurate (e.g. you may see the scene become slightly misaligned with the trigger, or tilting to one side).
Extended tracking works by looking for features in the environment around the trigger, and tracking how they move as the user moves. The app uses these movements to guess where the user is relative to the last time it 'saw' the marker. This means over time, and with more movenent, the scene drifts away from the exact center of the marker.
This environment-tracking approach also means extended tracking will not work well in changing environments, e.g. areas with lots of people, moving objects, or where the user will be seeing big changes in brightness.
Extended tracking will work very well when the marker is placed on a table or floor in an evenly-lit, static environment with lots of visual features.
Things to watch for when using Extended Tracking
- Reflective surfaces (glass, or shiny floors) can make the app track the reflections instead of the environment
- Shaking the phone while moving back can blur the image and lose tracking (this is worse in low light, so brighter is better)
- Big changes in brightness (e.g. starting in a dim corner, then a bright window comes into view as you move back) could lose tracking.
- Best advice to give to users: Move back slowly while keeping the camera steady and the trigger in the center of your view.
- Movement in the camera frame - if big parts of the camera view are moving (due to people passing by, or standing nearby) this will make the tracking lose accuracy.
Things that will help tracking
- Floors/walls with lots of detail & contrast around the marker- patterned carpets, rugs, posters, even objects like cables or leaves on the floor.
- A bright, evenly lit environment.
- Phones are preferable to tablets (as tablets often have low quality cameras)