Threading Successes of Popular PC Games and

Engines

Paul Lindberg and Brad WerthIntel Corporation

GDC 2008

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What’s this all about?

•Last year we had a great turnout for our hands-on tutorial on game threading.

•This year we want to focus on current commercial products and future pathfinding efforts.

•We’ll cover performance and feature enhancements from threading.

•This is a half day tutorial!

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What we’ll hit today

•Introduction•Supreme Commander•Gamebryo Element Engine•Hellgate: London

– Break!

•Intel’s n-core engine experiment•Allegorithmic’s Substance•Wrap-up

– Food!

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Why threading?

•GHz era – so over.•Multi-core is ubiquitous in gaming platforms.•Consumers demand validation of their purchase.

•Threading is still an unsolved problem for games.

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Let’s look at common threading themes for games

•Task (on a thread)

•Control Transition– Lock protecting shared data– Data copied to local data– Operation on local data

Task

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Render Split works well, but gains are limited

•Copy data necessary for calls to rendering APIs•Make all rendering calls from the same thread•Render one frame behind the simulation

Render

The Rest

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Work Crew or Pipeline moves a lot of data around

•Apply the Render Split concept everywhere

Render

Physics

Particles

Animation

Render

Physics

Particles Particles Particles Particles

Physics Physics

Animation

AI

Animation Animation

AI

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Operation Queue keeps data localized, and bandwidth down

•Keep the data in one place, but queue up operations on it• In a perfect world, reads are immediate, free, and consistent

QueueAI

Service

Animation

Physics

Render

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How are games today targeting multi-core?•Thread for performance

– Framerate– Load times– Easier path to smooth framerates, compared to time-slicing– Now very common

•Thread for features– Many possible CPU-intensive effects– Just starting to appear

•Use threaded middleware– Does whatever it does, and scales it out– Common, but how well do they work together?