GDC 2014

GDC 2014 Session Scheduler

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Concurrent Interactions in The Sims 4

Peter Ingebretson  |  Senior Software Engineer, Electronic Arts (Maxis)
Max Rebuschatis  |  Software Engineer III, Electronic Arts (Maxis)

Location: Room 304, South Hall

Format: Session
Track: Programming
Vault Recording: Video

In real life, people often do several things at the same time, but games typically limit agents to performing actions sequentially. For The Sims 4, we developed a system for authoring interactions that allows simulated people (called Sims) to express multiple concurrent behaviors. Interactions are largely data-driven and are defined in terms of constraints, which specify the state a Sim must be in to perform the interaction. Constraints are used to test whether interactions are compatible, and to drive decisions that Sims make about whether, how and where to perform an interaction. This system allows Sims in The Sims 4 to convincingly eat, watch TV, chat with other Sims, express emotion, and perform many more behaviors simultaneously. We believe that this powerful and simple technique could be applied to a similar effect in your game too.


Attendees will learn a powerful and practical technique for defining composable behaviors using constraints. Constraints can drive decision-making and allow multiple behaviors to be expressed simultaneously. This technique allows characters in The Sims 4 to eat, watch TV, and socialize with other Sims, all while sitting, expressing anger, and much more.

Intended Audience

The main audience for this presentation will consist of software engineers who are curious to learn a new technique to add to their toolboxes. The presentation will also be of interest to designers and producers, who should be inspired by the possibilities that are unlocked by constraint-driven behaviors. This presentation has no prerequisites.