title: Output of cv2.findHomography in OpenCV (Python)
body: <p>I'm using OpenCV's findHomography function (with RANSAC) in Python to find the transformation between two sets of points.</p>
  
  <p>Looking at the <a href="http://docs.opencv.org/modules/calib3d/doc/camera_calibration_and_3d_reconstruction.html" rel="noreferrer">documentation</a>, the output is a mask and a transformation matrix.</p>
  
  <p>The documentation is not clear about what the mask represents, and how the matrix is structured.</p>
  
  <p>Is a 1 in the output mask a point that fits the found transformation or a point that was ignored?
  And could you explain the makeup of the 3x3 output transformation matrix?</p>
  
  <p>Thanks in advance and sorry if I missed some documentation which explains this.</p>