From the previous chapter you've learned how to use special images called markers to augment a real scene. The strong aspects of the markers are as follows:
Cheap detection algorithm
Robust against lighting changes
Markers also have several weaknesses. They are as follows:
Doesn't work if partially overlapped
Marker image has to be black and white
Has square form in most cases (because it's easy to detect)
Non-esthetic visual look of the marker
Has nothing in common with real-world objects
So, markers are a good point to start working with augmented reality; but if you want more, it's time to move on from marker-based to marker-less AR. Marker-less AR is a technique that is based on recognition of objects that exist in the real world. A few examples of a target for marker-less AR are: magazine covers, company logos, toys, and so on. In general, any object that has enough descriptive and discriminative information regarding the rest of the scene can be a target...
