Two cameras are pointed slightly toward each other, like your eyes when you fixate on a nearby object. The green plane is the epipolar plane defined by both camera centers and the moving 3D point.
Cyan dots mark the camera centers and epipoles, magenta lines are epipolar lines, red dots show the projected point, the green transparent sheet is the epipolar plane, and the dashed green line is the baseline across both cameras.
Each magenta epipolar line lies on a sensor and passes through the epipole. As the point moves, its image is constrained to slide along this line—never leaving it.
Follow the green plane: it always contains both camera centers and the moving point. The red projections stay on magenta epipolar lines that all originate at the cyan epipoles. Pause the animation if you want to examine a specific position.
The cyan dot on each sensor marks where the baseline meets that sensor. All epipolar lines radiate from this spot.
The red dots are the projections of the moving 3D point onto each sensor. They always remain on their corresponding epipolar lines and share the same epipolar plane.