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'Knockout City's' Parallel, Deterministic, and Rewindable Entity System

Chris McEvoy  (Chief Programmer, Velan Studios)

Pass Type: All Access Pass, Core Pass - Get your pass now!

Topic: Programming

Format: Session

Vault Recording: TBD

Audience Level: No

We present a general-purpose game entity system that supports deterministic, parallel computation and the ability to rewind world state within a time window. Such a system can be used to support robust client-side prediction in a networked game, world state scrubbing at development time, and effective utilization of processing power on multi-core hardware. We discuss how the entity system, working together with our scripting language, ensures concurrent, deterministic, and efficient data flow, in a way that is largely transparent to users of the system. We show how this system was used on "Knockout City", an online multiplayer action game with dodgeball mechanics, to author everything from core gameplay to user interface and player progression.


An entity system is essentially a data organization problem coupled with a scheduling problem. While attendees will learn how we solved our data visibility, data lifetime, and compute scheduling challenges in the specific, the lessons described in this talk should be applicable to entity-data problems attendees will encounter elsewhere.

Intended Audience

Programmers interested in entity systems. A working understanding of data visibility in a multithreaded context will be helpful for portions of the talk.