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Posts Tagged ‘LOD’

Promised AI Count in Halo Reach

Sunday, February 14th, 2010

I was looking at my daily barrage of Google alerts on “game AI” (which tend to contain an annoying number of links to stories about Alan Iverson) and this article blurb from the Bitbag happened to catch my eye. It’s a preview of Halo Reach and seems to be a fairly thorough treatment. They talk about a lot of the different gameplay elements and how they differ from prior games in the franchise. They go into great detail about a lot of things. There was only a little bit of info about the AI, however. It said:

Bungie wants this game to feel a lot like Combat Evolved. They want Reach to be filled with open environments filled with enemies and allow you to figure out how you want to deal with the situation. There will be corridor battles like what we’ve seen in past Halos, but that will be balanced with the terrain of Reach. Reach will have a full weather system as well as Bungie saying they will have “40 AI and 20 vehicles” on screen at a time.

I thought that was kind of interesting simply because my first reaction was “is that all?” After a moment’s reflection, I realized that the number of AI on the screen in prior Halo games – and even in other shooters – is usually along the lines of a dozen… not 2 score.

On the other hand, it a game like Assassin’s Creed (my Post-Play’em observations), there were plenty of AI on-screen. However, the majority of them were just the citizens who, for the most part, weren’t doing much beyond animation and local steering (until you engaged them for some reason). The question about Bungie’s promise above, then, is how much level of detail scaling will there be with those 40 on-screen AI characters?

Typical LOD scaling has a tiered system such as:
  • Directly engaged with the player
  • On-screen but not engaged
  • Off-screen but nearby
  • On-screen but distant
  • Off-screen and distant

Each of those levels (in order of decreasing AI processing demand) has a list of things that it must pay attention to or a different timer for how long to wait between updates. How much of this is Bungie tapping into with Reach, or all they all running at the same LOD?
I know that the AI guys at Bungie are pretty sharp and go out of their way to pull of nifty stuff. In fact, ex-Bungie AI lead, Damián Isla just did an interview with AIGameDev on blackboard architectures (my writeup) where he explained how a lot of the Halo 2 and 3 AI was streamlined to allow for better processing of many characters. I’m quite sure that much of that architecture survives in Halo Reach.
Anyway, I just thought it was interesting to see the promised numbers. It will be even more interesting to see how the marketing blurb actually plays out on the screen in the final product.
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