Overview:

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.