title: Intersection of a line with the infinity plane
body: <p>I would like to compute the intersection of a 3D line with the plane at infinity. I suspect it would be the same as taking the 3D direction of the line and setting the 4th vector coordinate to 0.</p>
  
  <p>However, this is not enough. I would like to know the 2D position of the intersection in screen coordinates after the line is transformed and projected by a perspective camera.</p>
  
  <p>This problem is equivalent to finding the vanishing point in a 2D image.</p>