title: 2d pixel to 3d point conversion with known depth?
body: <p>I gone through some similar post for this problem like this,</p>
  
  <p>@RafazZ</p>
  
  <p><a href="https://stackoverflow.com/questions/51272055/opencv-unproject-2d-points-to-3d-with-known-depth-z/56985565#56985565">OpenCV unproject 2D points to 3D with known depth `Z`</a></p>
  
  <p><a href="https://stackoverflow.com/questions/38909696/2d-coordinate-to-3d-world-coordinate">2D Coordinate to 3D world coordinate</a></p>
  
  <p>as doing 2d to 3d conversion in camera_frame they have removed R,T matrix from calculation and only using like this,</p>
  
  <pre><code>x = (u-cx)/fx
  y= (v-cy)/fy
  
  actual (X,Y,Z)
  X= x * depth.at(u,v)
  Y= y * depth.at(u,v)
  Z = depth.at(u,v)
  </code></pre>
  
  <p>so, I want to understand why we can remove R,t from calculation like this when doing 2d-->3d in camera_frame?</p>