SimCity’s Glassbox Simulation Engine Details -- Sophistication Through Simplicity


Posted March 9, 2012 - By Jake Gaskill


Leading up to GDC 2012, one of the big rumors as far as reveals was that EA and Maxis would unveil a new SimCity game. Well, as you’ve probably seen by now, that’s exactly what happened. However, despite holding a special press event to officially unveil the game, neither EA nor Maxis talked at all about the game itself or provide any details regarding its development, aside from showing a pre-rendered target concept/SimCity announcement trailer.

Instead, EA relegated said info that people wanted to a lately added panel entitled "Inside the Glassbox,” a largely technical-based presentation about Maxis’ new simulation engine that powers the SimCity. For someone like me (i.e. someone with zero understanding of the inner workings of a computer simulation engine), it was a rather dense discussion to wade through.

Thankfully, the elegance and conciseness of the Glassbox engine itself, and the fundamental building blocks that drive it, made the presentation of the simulation elements, and even the code behind it, actually quite entertaining and educational. Better still, it made me genuinely excited about SimCity, a franchise that has held little appeal for me since I first played the original way back when.

Now, as you’d expect from a, as Maxis describes it, “next-generation simulation,” the nuts and bolts driving the various components in the game are incredibly sophisticated but intentionally simplistic at the same time. So while it’s easy to grasp things like, “agents carry resources from one place to another or paths (roads, pipes, etc.) guide people, resources, and such to destinations,” once you start combining them all and multiply the scale by factors of 1,000, things start to get a bit more complicated.

Sim City Game Engine Preview Video »

At one point during the presentation, Maxis used the example of a path with a house, a factory (job/destination), and some sims on it to demonstrate on the engine’s more rudimentary but essential functions. A fairly straightforward setup, but bringing this scenario to life requires several moving parts that must dynamically work together to achieve the final result.

To make the development and implementation of this delivery system as easy and effective as possible, Maxis has streamlined yet evolved the process of, as in this example, getting people or resources from one place to another (sims from home to work, water from pump to houses, etc.) while also giving the user the ability to incorporate new additions into the flow without interrupting the original system or requiring an entirely new one to replace it.

This particular feature also works in tandem with something called the Virtual Distance Field, which basically helps the agents assess where they want to go based on their position relative to their destination and whether it will be worth the “cost” of traveling there. So in this case, because there are five job slots open at the factory, the sims hop in their cars and head to fill those positions.

SimCity’s Glassbox Simulation Engine Details -- Sophistication Through Simplicity

Along the way though, a new factory is placed in between their homes and the first factory. Two sims had managed to reach the first factory before the second one was placed, so when the stragglers came along, they branched off and headed for the second factory because it was closer and had the most chances for placement since it had five open slots instead of three.

While similar simulation engines no doubt feature something akin to this, Maxis has made it a point to ensure Glassbox not only includes this functionality but is able to incorporate it in such a way that it can work dynamically with the other systems and features without the need for a lot of other systems to pull it off. This pretty much sums up Maxis’ entire approach with Glassbox and its design approach with SimCity as well: simplicity in, complexity out.

Another area where Maxis has focused a lot of attention has been on the consequences of actions with relation to natural resources. Not only are natural resources limited—as is the real world—how you handle those resources once you have them will have serious consequences on your city and its inhabitants.


To demonstrate this, we watched a scenario where a water pump was placed outside a zone consisting of a residential area and an industrial district. At the start, everything was peachy. The water pump supplied houses with clean water, the factory pumped out its goods, and the residence were happy. But after a while, the factory started seeping pollution underground, contaminating the water supply. Because the water pump wasn’t equipped with the proper filtration systems, the polluted water was then pumped to the buildings around the city. Workers in the factories started getting sick so they were sent home (and they aren’t able to return to work for a day), which meant there weren’t people to operate the factories, so production was brought to a grinding halt.

Again, it might sound simple enough (and in fact Maxis told the audience that we should be genuinely surprised by how simple it seems), but that’s only because the underlying systems have been designed in such a clear and concise way that once the designers start building them on top of one another, they are able to achieve incredibly elaborate yet totally logical results.

Here were some of the other big takeaways with regards to what Glassbox is allowing Maxis to achieve with SimCity:

  • Everything in the game is physics based now (i.e. people, buildings, vehicles, etc.).
  • “What you see is what you sim” and vice versa. Each sim in the world is an individual person. Instead of traffic density to represent cars, the game shows individual cars. You can see sims in their houses, at their jobs, going about their lives.
  • The level of detail the engine is capable of producing will make your cities feel alive and more tactile than ever before.
  • The engine is built with an eye on the future, and scalability is a major part of that vision, as it will allow the game to move from PC to mobile devices and back again without sacrificing the original quality.
  • Because the engine and game will include such a solid online infrastructure, it will allow Maxis to deploy updates and tweaks directly into the game very quickly; it’s also what allows the cloud save system to work so well, even if the Maxis servers take a dive.

We’ve obviously only just begun to see what Maxis has cooking with SimCity, but even from this somewhat heady introduction to the technology behind it, it’s clear Maxis sees it as a true benchmark for what a simulation game can be. And we’re just seeing a sliver of what’s going into the final product, and they have at least year’s more worth of work to do on it. That’s impressive (simpressive?TM).

SimCity’s Glassbox Simulation Engine Details -- Sophistication Through Simplicity


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