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Often times when a client is trying to select wallpaper, they get only a single iteration of the pattern, sometimes not even full-sized. Many quality suppliers will be able to provide a photograph of a room with the wallpaper in use - but even then, usually only in one particular color even if the style comes in many colors.
A combination of GIMP/Photoshop, and 3ds Max can give a client not only a good idea of how the wallpaper will look in use, but how it will look in the particular room and location they want it.
Sunflower Ogee
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One of my first 3D renderings for a client on the left, the finished
room on the right. The furniture and wardrobe were all custom
designed by Brendon Koo of Brenko Design.