Example 1: Converging cameras
Example 2: Near parallel cameras
In general epipolar lines are not parallel.
Degrees of Freedom
Epipolar geometry depends only on the relative pose (position and orientation) and internal parameters of the two cameras, i.e. the position of the optical centres and image planes. It does not depend on structure (3D points external to the camera).
There are 7 degrees of freedom:
The fundamental matrix is the algebraic representation of epipolar geometry.