This 3rd edition is set to be the most controversial — yet fascinating — Annual Awards for Game AI! Let me clarify. The whole procedure, including the nominations and the voting, is done by the community here at AiGameDev.com. Of course, there's a certain editorial process involved in picking the nominees, but the rest is mechanical and just a question of collecting the results.
Typically, I've been able to predict the winners... mostly. This year, however, that wasn't the case! I speculate this could be due to the following reasons:
It's been a very constructive year for Game AI, more games deserve the spotlight, and it's harder to separate the candidates.
The community is by definition self-selecting and this reflects in the way its best games are chosen...
I'm getting older, my taste in games is changing, and everyone voting in the awards thinks radically differently than I do. :-)
It's probably a combination of the three, but the bottom line is that I've decided to include as "Editor's Pick" along with the "Vote Winner" for each award. If anything, I hope this helps shine a spotlight onto more games that are worthy of attention.
Anyway, without further ado...
Best AI in a AAA Game
THE SIMS 3
The third major version of EA's money-making franchise hit the streets in February 2009. Don't be fooled by the numerous expansion packs that preceeded it, this release was a radical departure from THE SIMS 2 in almost every way, not least in the character AI department. The Sims' new personality traits, their ability to interact socially and behave autonomously within living neighborhoods all combine to make this a very unique simulation game.
A series of blog posts about Alice and Kev which was featured in mainstream media earlier this year is a perfect example of the kind of emergent storytelling made possible thanks to the game's new mechanics. This example alone classifies it as a significant milestone for AI characters in games. From the site, here's the description of the experiment:
“This is an experiment in playing a homeless family in The Sims 3. I created two Sims, moved them in to a place made to look like an abandoned park, removed all of their remaining money, and then attempted to help them survive without taking any of the game’s unrealistically easy cash routes.”
Richard Evans, the man behind THE SIMS 3 and also the AI from BLACK & WHITE at Lionhead, told me at the GDC last year that he managed to get "only" 80% of his ideas implemented in the game. I told him that any portion of his ideas was still probably better by 8x than anyone else would have done! His influence shows in the game, and only time will tell how the ideas behind this game will affect the industry as a whole or whether this is a series unique to Electronic Arts and the high production values it put into the game.
The combat AI that Guerrilla Games built over the past 7-8 years since Shellshock: Nam '67, including Killzone 1 for the PS2 and Killzone: Liberation for the PSP has arguably become the best in industry with this latest iteration. The enemy behaviors are dynamic and adaptive, showing off both linear sections and large open areas of the game thanks to its tactical reasoning.
The AI in KILLZONE 2 in particular shines in the Skirmish mode where you can play with computer-controlled bots in large open maps designed for multiplayer, and free of scripts and trigger boxes. The bots were intended for offline play where you have 7 bots on your side against 8 enemies, but you can also compete online with your friends against various combinations of bots. Not only were the bots fun to play against, according many reviewers including to Ryan O'Donnell of Area5.TV, but they even passed an informal Turing test with journalists from the CO-OP show (season 2, episode 1) and others:
“The bot thing is pretty amazing. I was telling you earlier that I was playing it and it was behaving in such a particularly clever way in this one area that I had to check that I wasn't play online.”
— John Davison, WhatTheyPlay.com
Some reviewers even speculated that Skirmish and multiplayer bots were included simply to emphasize the strength of the combat AI. You can watch some High Quality videos of matches against the bots in the Salmun Market or the Radec Academy.
Cooperative buddy AI that accompany you through the game (while actually fighting alongside you) is generally a hard problem that nobody has got entirely right to-date, and there's still room for improvement in Killzone 2's buddies. However, it's one of the best attempts yet and given the underlying engine there's even more potential. In particular, there's a balance to be found between the aggressiveness that can save you in tricky situations vs. buddies playing safe so you don't need to revive them too often.
Best Non-Player Character
Morrigan in DRAGON AGE
Because many different characters are required to set the scene in DRAGON AGE, individually the characters may not seem as polished as other games. However, as Kevin Dill points out, overall the characters make for a very compelling role-playing experience.
- The overall production values are outstanding. There is a wealth of high quality animation and voice acting that really brings the characters to life, as well as solid assets and rendering.
- Reasonably good facial animation, including expressions, gestures, and so forth. Nothing groundbreaking here, but a state-of-the-art execution of a very challenging set of problems.
- The level of detail in the social interactions. Responses vary on all sorts of features, so that if you replay the game with a different character, and do things in different ways or in a different order you will get very different interactions with the various NPCs. This does a lot for believability.
All this goes a long way towards explaining how games last 60 to 80 hours!
Chloe in UNCHARTED 2: AMONG THIEVES
In terms of quality and sheer polish, the characters in UNCHARTED 2 are unmatched. From the animation and motion capture to the voice acting and in-game dialog lines, including the AI behaviors. Everything fits together to create an entirely compelling character that not accompanies Drake around the world as he engages in combat, but also provides gameplay moments on cue.
Naughty Dog have done an impressive job with all the characters in the game, but Chloe in particular seems to have captured the attention of many gamers — and without the use of excess nudity!
Best AI in an Independent Game
AI War was the clear winner of the Best AI in an Independent Game Award. The game has become famous for its huge battles and over 30,000 active ships in the universe, but innovates on the RTS design front as well with its procedural population.
GALACTIC ARMS RACE
Ken Stanley's team are not only leading academic research in game AI, but they're setting an example by also building games around their ideas. In particular, they chose to tackle the problem of content generation using neural networks and evolutionary algorithms. Galactic Arms Race is a space combat and exploration game, as well as an application of NEAT technology to generate diverse weapon behaviors. The game is free to play and you can download it from the homepage.
Design Innovation in Game AI
Procedural Geometry in LEFT 4 DEAD 2
The original LEFT 4 DEAD won the Best AI Award last year, and the community voting felt the next iteration should win the design innovation award thanks to version 2.0 of its AI Director controlling changes in levels.
The Animals in WORLD OF ZOO
This game was suggested by Kevin Dill. Here's how he described the game:
“Although this isn't a game that most of us would play (it's target market is much younger), the characters are extremely well realized and, frankly, lovable. The team responsible for creating them was headed by Bruce Blumberg, who did some of the foremost research on believable agents while he was at MIT, and the quality of the result reflects his influence.”
Kevin continues with what makes this an important milestone for AI design:
“Their integration of tools made it possible for much of the AI development for their characters to be done directly by the animators and designers. In addition, a large part of their success in crafting so much compelling behavior for so many different types of animals in such a short time resulted directly from the tight integration between animation, engineering, and design, and their flexibility in working together to solve problems. Often a problem that was hard to solve with AI (for example) was easy for animators — or vice versa.”
AI Technology in a Supporting Role
The City in ASSASSIN'S CREED 2
Two years ago, the original ASSASSIN'S CREED won the award for Technical Innovation in game AI thanks to its crowds, and with the sequel Ubisoft has managed to raise the bar even further. The various cities in the game have come to life thanks to the various different pedestrians: their behaviors, their animations and their interactions. Each of these features add to the overall feeling of the game's environment.
Most significantly, the development team did an amazing job integrating the various elements of the city into the gameplay. The concept of social stealth remains, but you can now also leverage the thieves and courtesans to help with your missions — for instance to sneak past the guards. With the new pocket picking mechanic, walking through a crowd becomes more fun in the process as well!
The AI Director in LEFT 4 DEAD 2
This year's edition of LEFT 4 DEAD brought a few key innovations, including the ability for the AI Director to control the path that survivors have to take by blocking doors and alleyways, but also support for changing the weather patterns. The final scores in the voting suggests that both Valve's design is on the pulse of its gamers, but also that the marketing strategy is still working wonders!
Technical Innovation in Game AI
Combat AI in KILLZONE 2
If you take a look at the extensive list of articles on this site about KILLZONE 2's AI technology, there's little doubt that Guerrilla Games is not only a very open studio about what it does, but it's also very focused on pushing the technology that goes into its games. In particular, this is the first documented application of an HTN planner in a real-time action combat game, as well as a use of AI strategy that's essentially bridged the gap between RTS and FPS technology.
Knowing how the team, and it's Lead AI Programmer Remco Straatman, is keen to reuse and improve upon its existing technology, this makes for a very fascinating prospect for upcoming games from Guerrilla Games!
- Waypoint Cover Maps and Efficient Raycasts on PS3 in KILLZONE 2 (Insiders)
- Not in My Line of Fire! Sensible Combat Behaviors using SPU Jobs (Insiders)
- Where Did That Enemy Go? Threat Prediction and Reasoning in KILLZONE 2 (Insiders)
- The AI in KILLZONE 2's Bots: Architecture and HTN Planning with Remco Straatman (Premium)
- From Squad Tactics to Real-time Strategy: High-Level Multiplayer Bot AI in KILLZONE 2 (Premium)
Hero Planner in DEMIGOD
DEMIGOD was the most controversial nomination of them all. It generated instant love or hate responses on our official IRC channel and even on Twitter when I brought it up. However, the game is among those I played the most this year, and I only competed against the AI in its offline Skirmish mode. It turns out over 70% of players only experienced the game offline, possibly due to the networking issues the game faced at launch.
Either way, the AI opponents are nothing short of an incredible achievement. The game is a complex strategy game where the hero Demigod's persist over the duration of the game and make RPG-style decisions, and in other moments require RTS-style strategy to decide how to achieve gameplay objectives. Given the scope of the problem, and the way the team at Gas Powered Games solved it using a hybrid planning/optimization algorithm, I think this is quite an achievement!
- DEMIGOD's AI from Role-Playing to Real-Time Strategy with Dru Staltman (Premium)
- Goal-Based Action Optimization and the Hybrid Hero AI in DEMIGOD (Premium)
Most Influential Published Research
Multi-Agent Control in Adversarial Games
Over the past few years, animation research has become more and more relevant for character AI as it's been moving into the domain of control systems — for example how to create an optimal policy to traverse a motion graph using reinforcement learning. Such techniques are not only fascinating since they blur the gap between the low-level motion capture and the high-level goals, but they address a real-world need of being able to make trade-offs between these two opposing sides.
This particular paper builds on previous work in the field by tying in the traversal policy of motion clips together with gameplay dynamics of two player games. Sometimes there simply is no optimal policy and playing randomly withing known distributions is the safest bet. See the paper and its accompanying video for more details!
Multi-Agent Control in Adversarial Games Download PDF
An Architecture for Game Behavior AI: Behavior Multi-Queues
This paper elegantly avoids the common pitfalls of game AI research by tackling a problem that's relevant to developers, by respectfully citing recent work from the games industry, and building on commonly used techniques. That's quite a noteworthy achievement in itself, which few other papers from 2009 manage to equal.
On top of that, the solution is elegant and not very far from what developers are using in industry. Behavior trees are a great architecture to build at the base of any game AI architecture to help connect different components together, and being able to support coordination (one increasingly important problem) is an added bonus.
An Architecture for Game Behavior AI: Behavior Multi-Queues Download PDF
Also check the following articles on the topic of behavior trees and coordination:
- Behavior Trees for Next-Gen Game AI (Insider)
- Coordinating Agents using Behavior Trees with Ricardo Pillosu (Premium)
Both objectively from my coverage of the games and their technology this year, and subjectively via my involvement with KILLZONE 2*, I feel this has been a great year for game AI as a whole — even compared to last year. It makes for a very promising decade ahead!
On a more personal note, I've now been working full time (and more) on AiGameDev.com for over a year now. From the many links and references scattered around this article, I hope it's obvious to what extent we've tracked down and documented the great applications of game AI this year. This is a huge part of why we exist, so thank you for your support and best wishes for 2010!
*: Yes, that means all the votes were rigged. Not. :)
If you have any thoughts or comments, don't hesitate to post them in the forum thread...