1. A method for guiding scanning of an intraoral cavity of a patient, the method comprising: capturing a first two-dimensional viewfinder image of a first portion of the intraoral cavity of the patient, the first viewfinder image corresponding to a field of view of an intraoral scanner using viewfinder imaging optics; generating a first topography scan of the first portion of the intraoral cavity by measuring one or more characteristics of returning light beams generated by illuminating the first portion of the intraoral cavity with the incident light beams by imaging optics, the first topography scan corresponding to the first viewfinder image and at least a portion of the imaging optics sharing an optical path with said viewfinder imaging optics; capturing a second two-dimensional viewfinder image of a second portion of the intraoral cavity, the second viewfinder image overlapping with the first viewfinder image; determining an area of overlap of the second viewfinder image with the first viewfinder image; and displaying one or more indicators of the area of overlap on one or more locations of a display.