How to understand cos window (motion model)?

Hi,foolwood!
Thanks for your Openning source code about Siammask first. And I am very interested in it. But when I read the code, It seems I cannot understand the real meaning of variable "penalty_k " and "window_influence " in tracker_config.py. I think maybe I do not understand cos window(motion model).

Start with tracker_config.py and trace where penalty_k and window_influence are used in the tracking pipeline. Compare those uses with the cosine-window and motion-model terminology; done means providing a clear explanation of both variables and how they affect tracking behavior.

Written by the indexing model from the issue text.