title: Mapping a 3D rectangle to a 2D screen
body: <p>I've searched SO but I just can't figure this out. The other questions didn't help or I didn't understand them.</p>
  
  <p>The problem is, I have a bunch of points in a 3D image. The points are for a rectangle, which doesn't look like a rectangle from the 3d camera's view because of perspective. The task is to map the points from that rectangle to the screen. I've seen some ways which some call "quad to quad transformations" but most of them are for mapping a 2d quadrilateral to another one. But I've got the X, Y <strong>and Z</strong> coordinates of the rectangle in the real world so I'm looking for some easier ways. Does anyone know any practical algorithm or method of doing this?</p>
  
  <p>If it helps, my 3d camera is actually a Kinect device with OpenNI and NITE middlewares, and I'm using WPF.</p>
  
  <p>Thanks in advance.</p>
  
  <p><strong>edit:</strong>
  I also found the 3d-projection page on Wikipedia that used angles and cosines but that seems to be a difficult way (finding angles in the 3d image) and I'm not sure if it's the real solution or not.</p>