Think of the most impressive, memorable video games of the last 40 years and they tend to have one thing in common: unity of vision. From the sludgy corridors of Doom to the vast art deco chambers of Bioshock, great games take place in intricately realised worlds where every aspect – from armour to architecture – reflects a consistent visual theme. As in the movie industry, the creation of detailed virtual worlds often involves the production of concept art – reams of sketches and paintings, based on early script drafts and discussions, fashioned to provide a target look for designers, artists and coders. "The idea is to establish the big picture of the game, like a visual pitch, not only for artists and designers, but pretty much everyone on the team," says Emmanuel Petit, lead visual designer at Arkane Studios. "I believe this helps in keeping us energised, and gives us something concrete and exciting to work towards."