There is something that I really like to practice. Something between collage, retouche and a bit of 3D. One of my clients wanted me to produce a quick raw image to explain his intention and its visual impact for a shopping mall project. Of course you have no time to construct the whole place in 3D with all its necessary lightning and details. To start the work I have a photo and a plan showing where the new elements would be.
First I made a quick copy of the original jpg, saved it in Maxwell as an HDRI and used it as a light source and a background image. Then, I positioned my camera to fit the new escalator in my scene like this…
The rendering is then extracted from its background, placed in the original image and edited with some new elements like logos, people ect… and here you get the result, a 3D graphic mix made in two days of work.
It has a different flair than pure CG work which had taken a week or so but still makes a nice illustration.