Another short geometric problem inspired by a work by Felice Varini (see previous exercise).

Problem: consider the following artwork:

Question: is there a "correct" viewpoint in the room even if you remove the (flat) mirror?

Solution: yes and no; there is still a correct viewpoint; unfortunately, it is not in the room; it is at least one meter under the feet of the photographer.  Exactly, the correct viewpoint is the point symmetrical to the viewpoint of the photo w.r.t. the plane of the mirror.

Consider only the boundary of the mirror as seen in the image.  Hypotize that the mirror is circular and horizontal. Does this allow you to determine the height (relative to the mirror) of the viewpoint of the photo? No.  Is there a way to compute it, and what of the following would you need?

• The camera intrinsic parameters
• The mirror's radius