P3D 3D perception and animals

[Deb <vrx@xxxxxxxxxxxxx>]

There are many ways of sensing depth or 3D.  These include "shape from
shading", prior knowledge, occlusion of far objects by near objects,
relative motions of objects when the observation pit changes, and of
course stereo views.

I think the relative motion is why birds move their heads so much when
they are looking at things.

I know that computer vision people have also sensed depth from one
camera moving forward, such as looking out the cockpit of a jet.  It
turns out that the position and velocity of objects in the image
determine their distance.

I suspect that birds use this to see in 3D even though they don't have
an overlap in their field of view.

They must have a very effect 3D because they come into a tree at high
speed and find a branch to perch on in a split second.

Al



------------------------------