Check with whoever made the picture you were looking at.  I haven't seen  where you got the original idea so I don't know exactly what they were doing. 
      Back 15 or 20 years ago I had a copy of a small program that was more than amazing for a home computer for the time.  What it did was allow you to give it 2 pictures then select points that were similar spots on both photos or images.  Such as each corner of the mouth would be selected, the corners of the eyes and so on.  Things that define the shapes and sizes related to the two faces.  Once enough points were selected you could tell the program to run the morph and it would morph the one face or figure into the other.
  What you saw if it wasn't a professional film and had the subject stay in one place could have been done with a modern version of just such a program rather than with Poser or DS.