@lyndamcg It was pretty straightforward really Linda. It's done using layers in Elements. Firstly you decide where to put your door. Copy your original and cut out your door oblong in your copy and place it on the original. Then using the Image Transform tool, stretch the outer edges of the door using the Distort or Perspective tool and then make another layer for the side edge of the door using the same technique. If you Google Geometric Landscapes there are some amazing images there. Hope this helps!
Sooo .. impressive. It hurts my mind a bit too - trying to work out what is what and what came from where but knowing that it all somehow looks so naturally believable. I love your virtual sculpture.