User projection-based AR, a projection is rendered on the target surface itself. This target surface could be anything, such as building, person, room, and so on. To render this kind of projection, the system needs to know the exact dimensions of the target surface, and then using single/multiple projectors, it renders the projection on the target:
Phone dialer pad projection over the hand
In the preceding image, the user is viewing a projection of the phone dialer on the palm of their hand.