Drag the mouse above the applet to move around the world ...
And click any key to toggle the state of the applet and drag the point M around ...
Things become interesting with a second viewpoint.
If we know m the projection of a point M onto a camera,
its corresponding point in
the other camera is contrained to lie on a line. This line is called
the epipolar line, and the correspondence between m and this line is
described by the Fundamental matrix.
The epipolar lines are the trace of the plane (C1,C2,M) in the
retinal planes.
Notice that the points e-c1c2 and e-c2c1 don't move as you drag M arround.
They are called the epipoles. It is where one camera is seen from the
other camera.
Lets consider a third camera. In each camera, the epipolar lines related to the 2 others cameras are now crossing at a point. If a point M is registered within two images, its projection in the third one is uniquely defined, through the Trifocal tensor . Notice how the two epipolar lines merge into one when the point M approches the plane (C1,C2,C3) called the trifocal plane.