Re:Some impressive things (Score 2, Interesting)

Step 1) Get lots of photos of a given subject

Step 2) Process these photos and find "similar points"

Step 3) Start correlating points on separate photograps

With enough points in common on two or more photographs, you can begin to get an idea of the 3D relationship between the points, and also the cameras taking the photographs.

There are applications that allow you to do Step 2 manually (the clearest example of the process I found was http://www.3dphoto.dk/UK/technique-UK.htm), but Photosynth appears to do it automagically, which is the cool part.