title: OpenCV calcOpticalFlowFarneback source code
body: <p>Where can I find the Python source code for OpenCV calcOpticalFlowFarneback (<a href="https://docs.opencv.org/3.0-alpha/modules/video/doc/motion_analysis_and_object_tracking.html" rel="nofollow noreferrer">https://docs.opencv.org/3.0-alpha/modules/video/doc/motion_analysis_and_object_tracking.html</a>)? 
  I tried looking up various sources and documentations but I couldn't find a reference to the code. I also browsed through OpenCV github repository but was unable to find it. 
  Can some please refer me to it?</p>
  
  <p>Basically, I want to know if there is any 3D implementation of Optical Flow Farneback or any other dense optical flow. I have realized that OpenCV calcOpticalFlowFarneback  is only applicable for 2D images.</p>