Understanding fiducial markers

A graphic marker is both the popular metaphor for AR technology (since people associate it with some mysterious symbols printed on paper) and its weakness (since it means that additional equipment is required for AR applications to operate). The need for additional equipment to operate AR applications is often considered their disadvantage, and hinders the popularity of AR games because players can sometimes be lazy and don't want to print out the markers. Nevertheless, the graphic fiducials have very important advantages: first of all, they require less calculation power, and secondly, they are pretty accurate because fiducials are friendly for computer-vision systems and very accessible to perform digital image scanning.

Engineers have tried to "teach" machines to read some printed data by using optical sensors since the end of 1940s. However, the machines were not good at learning human alphabets because doing so would take a long time. Furthermore...