Gamasutra interviews Ocean Quigely from the Maxis team on SimCity:

Ocean Quigley has been at Maxis since 1995. In that time, he’s been an artist and art director, and now serves as creative director on the company’s newest SimCity title — which is due to be released next year, simply under the title SimCity.
This game marks a new horizon for the series: For the first time, computing power has increased to the point where the simulation can be built from the ground up, with individual simulation elements (Sim citizens, buildings, vehicles) able to react to one another to produce a full city simulation. Previous games in the series faked granular detail.
As an artist, Quigley wants the game to visually portray information to the player as much as possible — to instantly represent decisions in the world itself, rather than forcing the player to look at charts, graphs, and menus.
Quigley explains the work he and others at Maxis have done to achieve this, and how the team makes creative decisions that impact not only the simulation, but also bring forth satisfying decisions for players and also accurately reflect the ways in which these systems interact in the real world.
You’ve talked about tilt-shift as a visual trademark for the new game, and how aesthetics can convey information. How important is it that the aesthetic choices you make in the game also convey information to the player?
Ocean Quigley: Let me answer that a couple different ways. One answer is that in previous games like SimCity 4, for example, we had an aesthetic of piled-on detail, without necessarily giving it meaning or giving it context. So, for this SimCity, basically, the simulation is sophisticated enough and complex enough that if we don’t take every moment, if we don’t take every opportunity to tell the player what’s going on in their city, then, basically, the art’s not doing its job. The simulation would be difficult to parse.

So, I’ve got a big slide, aesthetic commandment for all the visuals in the game: that if we can assign meaning to something, then we assign meaning to it. We really try not to put anything in the game at all that doesn’t serve as a UI function to tell the player what’s going on in their world.
So, you look at it and you think, “This is a city.” You’re looking at a city, you’re looking at architecture, you’re looking at buildings, and all that is true but what you’re really doing is you’re looking at UI that’s telling you the state of the simulation. The UI is just aesthetically stylized to look like the city.
To quickly touch on this idea of meaning, is all the information you convey via the game just about the state of the world? In other words, is all the meaning that comes — other shades of meaning — does that all come from the player?
OQ: So, of course the player is going to be projecting their own story and their own imagination on it. I don’t know enough about what the player is thinking to anticipate that. All I can do with integrity, or all I can do with legitimacy, is faithfully represent the state of the world at any given moment.
So, for example, if you see a car parked in front of a building, it’s because there’s somebody inside that building. And if there wasn’t anybody inside that building, the car wouldn’t be there. Or if the lights are on in the building, it means that the power is on, and that there’s somebody inside that building. Or if you see green terrain, it’s because that terrain is watered. Or if you see a house with graffiti on it, it’s because a crime has occurred there, and so forth. Right?
So, what I’ve got to drive the meaning in the game is the actions, the behavior, the state of the simulation. That’s what has to come out in the surface.
Of course, there are a lot of choices about what the simulator is doing that are happening at a deeper level, and there are aesthetics to that as well. But assuming you’re primarily talking about the visual aesthetics, they’re there to communicate to a player the state of the world that they’re creating.
Is there such a thing as a simulation aesthetic, or an aesthetic of simulation?
OQ: Yeah, yeah. Of course. It’s really about the cause-and-effect relationships between things and how you want to bind it together, those causes and effects.
So, for example, we could have people in a house get sick for no reason. They go to the hospital and get cured, but that’s kind of unsatisfying. You’d rather bind the fact that they got sick to something that is in principle, and hopefully in practice, understandable and parse-able by the player, right?
If they got sick, maybe they got sick because a patient zero came into the city and carried a disease with them. Or maybe they got sick because they drank polluted water. Or maybe they got sick because they lived downwind from the toxic chemicals of an industrial plant.
And so the simulation aesthetic is about drawing the cause-and-effect relationships between things and giving them integrity the player can understand, and not just doing things as smoke-and-mirrors, but having it be like a watch, where all the gears visibly move the other gears forward and the whole thing has got an integrity — almost a mechanical integrity of all the pieces stacking into each other and moving each other in a way that the player can understand.
And then, of course, it’s up to you as the designer of the game to figure out how you want to make those relationships work. You want to have crime be a function of education, or lack of education, or crime be a function of employment, or do you want crime to be a function of pollution of the environment, do you want crime to be intrinsic to people, do you want tie crime to class? Those are all the sorts of simulation aesthetic decisions that you make as a designer of a simulation.
And then you try to decide if it makes sense, if it has coherence and integrity, and is it something I can express to the player? And so that’s kind of what simulation aesthetics is. It’s the art’s job to express that to the player. Of course, there’s a feedback loop there, because, if you want to express something that’s so abstract that you can’t surface to the player, then there’s really not a whole lot of point to do it. So the aesthetics that you make in the simulation are constrained, let’s say, and not entirely bound, but constrained, by what you can transparently present to the player.

Read more over at Gamasutra