The art director for a game is essentially the one who decides what the game you’re playing will look like, in a nutshell. But this means being responsible in some way for each and every element in a scene, how they come together, which elements to use, and what those elements are in the first place.
Of course, this requires a lot of interaction with the rest of the team, and the ones who will be actually making the items and scenery in question. The art director is basically the one who takes the ideas of the game designer, and organises them into something visual; he or she has the final say in everything visual that goes into the final product. If the designer says s/he wants the first level to be a rainforest full of life and energy, the job of the art director is to see the designers vision as clearly as possible, translate that rainforest into visual form, and ask themselves firstly, ‘What does a rainforest look like? What types of trees and plantlife would one find? What is the ground like?’, and secondly, ‘How can we put that life and energy into the level?’ Maybe they will decide to fill the area with movement from every direction; ‘Rainforests are full of insects and animals, so the background needs to be full of…?’ And so they do the research to find out exactly what insects and animals one would expect to find in a rainforest. ‘So, this rainforest needs tropical butterflies, hummingbirds, treesnakes, etc. But will they be static or animated? Sprites or 3D models? Maybe if the player leaves their character standing still for too long, insects will gather around him. Aha, maybe if this happens, the character swats them away.’ So already, the art director is telling the lead artist s/he needs x number of different models for Cacao Trees, Cecropia Trees, and Canopy Trees, at least one static model for an iguana, several hummingbird models (fully animated), a treesnake model (also animated), an animated sprite of insects, and a new idle animation for the main character.
However, the designer may well say s/he wants to scrap the rainforest and go with a desert instead, but it still needs to keep the feeling of life. This is a more difficult; ‘How do I put life into a desert?’. Firstly, they consider what can be reused from the original scene. ‘Maybe that model of a snake could be retextured to make it a rattlesnake? Perhaps some of the more ambiguous shrubbery could be reused around an oasis?’.The art director is responsible for how the final result turns out. Once a task is completed, it’s run by the art director, who must give the go-ahead for it to be used in-game. So if the wrong trees are used, or if the texture of the ground mismatches the environment, or even if the plantlife is too green for the designers vision, the art director is the one who takes responsibility.