Inverse Projection Problem

Inverse Projection problem is the fact that a particular image on the retina can be created by many different objects. The book states it an easier way which makes more sense to me. It basically says that if we already know an object that we can determine the shape of the object's image on our retina, but that image can be created by a large amount of objects. On page 102 of the book there are two pictures of rocks that when viewed at a certain perspective it looks like they are circular but if you view it from a different angle it is just random shapes. This basically shows that we can make something circular out of a bunch of things that aren't circular at all. We solve this problem by viewing things from different perspectives along with knowledge we have from past experiences.