Lucas Kanade Optical Flow, Direction Vector

Question

I am working on optical flow, and based on the lecture notes here and some samples on the Internet, I wrote this Python code.

All code and sample images are there as wel

Answer 1

@belisarius says "LK uses a first order approximation, and so (u,v) should be ideally << 1, if not, higher order terms dominate the behavior and you are toast. ".