title: OpenCV Explanation solvenpn
body: <p>Can anyone give me more explanation about the opencv function <code>solvepnp()</code>? 
  The opencv documentation says </p>
  
  <pre><code>bool cv::solvePnP   (
          InputArray      objectPoints,
          InputArray      imagePoints,
          InputArray      cameraMatrix,
          InputArray      distCoeffs,
          OutputArray     rvec,
          OutputArray     tvec,
          bool            useExtrinsicGuess = false,
          int             flags = SOLVEPNP_ITERATIVE)
  </code></pre>
  
  <p>I'm wondering what the <code>objectPoints</code>, <code>imagePoints</code> and <code>cameraMatrix</code> are. I have once calibrated my camera and have a parameter xml file from it, can i use this? </p>