At last week’s Game Developers’ Conference I delivered a talk titled “AI-driven Dynamic Dialog”, describing the dialog system used in Left4Dead, Dota, and basically all of Valve’s games since The Orange Box.Summary graphic of voice-rules database

A PDF export of the slides for my talk is now available here. I’ve also created a support page where I’ll gather all information, bibliography, and followup associated with that particular talk.

I’ve also posted the the videos mentioned in the slides (since obviously they can’t be embedded into a PDF):

  1. Two Bots: Environment-Aware Speech
  2. Two Bots: Starting a Conversation
  3. Two Bots: Memory and Context
  4. Left4Dead2: Variety
  5. Left4Dead2: Automatic Barks
  6. Left4Dead2: Environmentally Triggered Dialog

Thanks to everyone who stuck with me through late flights and laptop failures to the last session of GDC 2012!


  1. Ed Macauley says:

    Awesome stuff. Thanks for an entertaining and informative talk.

  2. Zvi Effron says:

    Wins my vote for best talk of GDC. I’m also seeing a lot of interesting ways to use this system for things outside of dialog.

  3. Elan says:

    That’s great to hear, thanks! We’re thinking of using it to drive behavior and things like the L4D director as well. It’s only occurred to us recently that the system we built for dialog might have other applications.

  4. Charles Zapata says:

    +1 on best talk at GDC. Really compelling content and dynamic presentation. Great to see simple, powerful systems in action.

    (And I wasn’t really going to play L4D before this – now I’m going to give it a shot.)

  5. Phrontisterion, and some more thoughts about tools and the art | Emily Short's Interactive Storytelling says:

    [...] Yang comparing Varytale and specifically the structure of Bee to the rule-based dialogue work presented by Elan Ruskin at GDC 2012: both are looking for the most specific event they can trigger. I hadn’t thought of that line [...]

  6. Jimmy Gorham says:

    Hi Elan, wanted to post to thank you for spreading this fantastic information. I am a game designer who was tasked with designing a conversation engine from scratch and after beating my head against the wall for a bit I stumbled upon this post via Valve’s website. First of all, THANK YOU. Second, it is remarkable and inspiring that you choose to take information of this caliber and spread it to the world rather than hold onto it as some private treasure. You have done a great service to the gaming community, one that I hope to repay someday. Thanks.

Leave a Reply