Wrong flow on human limbs

[gengshan-y]

Hi, sorry for duplicating. I opened an issue with the same title in the original repo of gamehook_gtav, and decided to bring it here just for visibility since the original repo seems to be out-dated.

The details are here. The code works great for optical flow of rigid background and cars, but not perfect on the human. It would be great if you could look into this issue or share your thoughts on how to debug it. Thanks!