title: How to determinite orientation of camera whout OpenCV recoverPose() method?
body: <p>I want to determine the orientation of the camera for each frame in a video. I'm looking at the <code>cv2.recoverPose()</code> method, but I have found two personal issues with it:</p>
  <ol>
  <li>It requires the Essential matrix. The only way to find E with openCV is by passing 5 points to <code>cv2.findEssentialMat()</code> which is a lot of points! I would rather have just 2 points to find the orientation. I believe there are other ways of estimating it but that leads me to my second problem.</li>
  <li>These &quot;recovered poses&quot; seem to be estimations and not all that accurate. Maybe I'm wrong. How accurate is it?</li>
  </ol>
  <p>One unique thing about my circumstance is that I know the 3d position of both the center of projection of the camera and any reference points that the camera may be looking at. I know what your thinking: if I have the 3d location why can't I determine the orientation? Just assume that its not reasonable to do so. I think that I could use <code>cv2.projectPoints()</code> or some similar method to determine the orientation of the camera, but I'm not exactly sure how.</p>
  <p>Anyone have ideas?</p>