Load a clip of an LBW appeal from before DRS existed, mark the pitch and the ball by hand, and the ball-tracking geometry is solved from that single camera — pitching, impact, and whether it was going on to hit the stumps.
Awaiting marks
Click a label, then click that exact spot in the frame. Mark everything you can see at both ends — the bowler's-end stumps are the most valuable marks on the screen, because without a height reference far down the pitch the lens is unconstrained.
Step frame by frame and click the centre of the ball. Mark the flight before it pitches as well as after — that long arc is what fixes the ball's speed, and speed is what fixes its depth down the pitch.
Rendered from the solved trajectory on a fixed virtual camera, so every clip produces the same framing. Screenshot or copy this for the video.
Ball centre inside the stump lines is hitting; centre outside but the ball still clipping is umpire’s call.
The corridor is the width of the stumps extended down the pitch.