An example of polar based optical flow algorithm can be found here .
For details see A polar representation of motion and implications for optical flow , In the Proceedings of the IEEE International Conference on Computer Vision and Pattern Recognition (CVPR),, Colorado Springs, USA, June, pp. 1145-1152, 2011.
The polar based optical flow was implemented as an additional class in the Sun optical flow package.
See [D. Sun, S. Roth, and M. Black: Secrets of optical flow estimation and their principles, CVPR 2010] paper and Sun's home page ).