The output optical flow vectors are velocity vectors or displacement vectors?

I am working on a project with optical flow (HS and LK), but I need to understand if the output flow indicate velocity vectors or displacement. Does anyone know?

Thank you very much

Answer 1

[Binaya]

Hi Nicole, 

 

Based on the provided description, it seems that you would like to understand what the output object of the optical flow signifies.

Please go through the following explanation to your query:

1. Optical flow methods such as Horn-Schunck(HS) and Lucas-Kanade(LK) estimate the motion of every pixel between two consecutive frames in a video.
2. The vectors generated in the optical flow field are velocity vectors that store direction and speed of a moving object.
3. As the two images used for calculating the optical flow field are separated in a given time frame, the optical flow output is interpreted as velocity vectors.

Please refer to the following documentation to learn more about the opticalFlow:

1. opticalFlow: https://www.mathworks.com/help/vision/ref/opticalflowobject.html

 

I hope this helps. 

Regards  

Binaya  

[NICOLE LONGHI]

Thank you very much! So the vectors are velocity vectors, and now the question is, how does the optical flow draw the vectors on a frame? Why those directions? Are they velocity directions? is not very clear to me