title: PointCloud from two undistorted images
body: <p>I want to do some Structure from Motion using OpenCV. This should happen on Android.
  Currently I am  having the cameraMatrix (intrinsic parameters) and the distortion coefficients from the camera calibration. </p>
  
  <p>The user should now take 2 images from building and the app should generate a pointcloud. 
  Note: the user maybe also rotates the camera of the smartphone a little bit as he moves along one side of the building...</p>
  
  <p>At the current point, I have the following information:</p>
  
  <ul>
  <li>the undistorted left image</li>
  <li>the undistorted right image</li>
  <li>a list of good matches using SIFT</li>
  <li>the homography matrix</li>
  <li>the fundamental matrix</li>
  </ul>
  
  <p>I've searched the internet and now I am very confused how I should proceed...
  Some say I need to use stereoRectify for getting Q and use Q with  reprojectImageTo3D() for getting the pointCloud.</p>
  
  <p>Others say that I need to use stereoRectifyUncalibrated and use H1 and H2 from this method to fill all the parameters of triangulatePoints.
  In triangulatePoints I need the projectionMatrix of each camera/image but from my understanding this seems definitly wrong.</p>
  
  <p>So for me there are some problems:</p>
  
  <ul>
  <li>How do I get R and T (Rotation and Translation) from all the information I already have</li>
  <li>If I use stereoRectify, the first 4 parameters are cameraMatrix1, distortionCoeff1, cameraMatrix2, distortionCoeff2) - If I do not have a stereoCamera like Kinect, are the ameraMatrix1 and cameraMatrix2 equals for my setup (mono camera on a smartphone)</li>
  <li>How can I obtain Q (guess if I have R and T I can get it from stereoRectify)</li>
  <li>Is there anonther way of getting the projectioMatrices for each camera so I can use the triangulationmethod provided by OpenCV</li>
  </ul>
  
  <p>I know this are a lot of questions, but googeling confused me so I need to get this straight. I hope someone can help me with my problems.</p>
  
  <p>Thanks</p>
  
  <p>PS as this are more theoretical questions I did not post some code. If you want / need to see code or the values of my camera calibration, just ask and I will add them to my posting.</p>