Threading Successes of Popular PC Games and Engines

1
Threading Successes of Popular PC Games and
Engines

• Paul Lindberg and Brad Werth
• Intel Corporation
• GDC 2008

2
Whats 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.
• Well cover performance and feature enhancements
  from threading.
• This is a half day tutorial!

3
What well hit today

• Introduction
• Supreme Commander
• Gamebryo Element Engine
• Hellgate London
• Break!
• Intels n-core engine experiment
• Allegorithmics Substance
• Wrap-up
• Food!

4
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.

5
Lets look at common threading themes for games
Task

• Task (on a thread)
• Control Transition
• Lock protecting shared data
• Data copied to local data
• Operation on local data

6
Render Split works well, but gains are limited
Render
The Rest

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

7
Work Crew or Pipeline moves a lot of data around
Render
Render
Particles
Particles
Particles
Particles
Particles
Animation
Animation
Animation
Animation
Physics
Physics
Physics
Physics
AI
AI

• Apply the Render Split concept everywhere

8
Operation Queue keeps data localized, and
bandwidth down
Physics
AI
Render
Queue
Service
Animation

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

9
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?