The sky was not randomly selected. I wanted enough clouds threatening, dark but with a gleam.

Thus placed it in bottom of the image

I found this photograph interesting, because it had a good prospect, and then could seem to be a carcass of completely destroyed building, I thus integrated it. Found on: http://www.imageafter.com

Then I added a smoke on the top of the image using the brush with a very light flow.



Best moment, in any case for me, the research of the debris for the tower. And those are placed behind the building. These also find out in google image search.



Then I started to draw the prospects, to place the best possible debris. There are two solutions, either trace them, while following the edges of the building, or you can create a grid with vertical & horizontal features, For the debris of the right part, I recopied a part of the ruins of the tower, then reverse the direction.

Remove the line of bicycles and a part of ground of the 3rd stage of the car park; I select the zone with the polygonal lasso tool. I took again the necessary details with the polygonal lasso (a little read high in the tower), which I recopied at the good places.



For the most important zone, lots of patience required because the placement is a little delicate.

Voila, here is the final scene :)



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