2 Replies Latest reply on Nov 26, 2015 1:33 PM by trey38647

    Why render background and foreground elements in separate passes in a 3D CGI animated scene?

    trey38647

      Imagine a 3D CGI animated scene (not a stereoscopic scene where you need the glasses but a regular 3D CGI scene).

      '

      In the scene there is a main area (let us call this the background element) and the foreground area or foreground element.  The background element in the scene has a car driving on the road in the countryside.  The foreground element consists of trees and shrubs growing on the trees. The shot is for 4 seconds and the camera move is a simple camera tilt upwards, where the the camera is located up at the crown of a tree and behind that tree and the camera tilts from down to up as it looks at the car driving in the background.

       

      It is recommended to render elements (background, foreground etc.) in separate passes and composite them in post-production.

       

      The question is:

       

      Why is it advisable to render background and foreground elements in separate passes in a 3D CGI animated scene? In the shot example above, why not render the background and foreground together in the same pass?

       

      To boost this argument, I read somewhere online from an excerpt from a book that said the below:

       

      "Moreover, it is also common to render components of 3D animated scenes, such

      as the background and foreground elements, in separate passes to be composited

      in post."

       

      Why is it common to render the components separately in the animated scene?

       

      Thanks!