Ok... this really isn't observations on the AI of Team Fortress 2. It is one of my weekly columns that I write for AIGameDev.com entitled "Play First... Code AI Later". In it, I talk about how observing other players online (especially the bad ones) really helps make me a better AI designer and programmer. There is much to learn from watching the differences between how the good players approach things when compared to the less-than-stellar tacticians. Most of it is on a tactical level... not anything to do with pathfinding, aiming, etc. This is more about how to think as a soldier (or engineer in this case).

Anyway, hop on over... it's actually rather long. Yeah... there's definately a rant tone to it at times. *shrug* Sorry...

Labels: AIGameDev, TF2

I will preface this commentary with three things:

A) We got a copy of Tenchu Z for free.
B) My 13-year old step-daughter (a black belt in taekwondo) is enamored with ninjas and the like - which is the only reason why I even broke the seal on this game.
C) I didn't get too far into the game - so if it gets better as it goes along, I missed out.

I can write off the game design itself as perhaps being "not my style", but from an AI standpoint, this game is just plain bad. Even my step-daughter, with her rudimentary knowledge of game AI (just from being in the same room with me often enough) was pointing out the obvious issues it has.

Advertising States

First off, welcome to the land of plainly exposed finite state machines. The enemies may have well been traffic lights since they were broadcasting the very few states that they had. I haven't touched the game in a few weeks, but off the top of my head, they were... Pace, alarmed, sniff (yeah, sniff), chase, fight, panic, die. Sure, there were some sub-states in there, but those were pretty much just to animate the characters.

What's more, some of the states were not even necessarily dependent on the environment. I watched two guards arrive together at a point, stop, give a brief salute wave to each other, chat, turn and go back to pacing. I thought that was at least minimally cool. But then, one of the guards got distracted and was behind the pace of the other quite a bit. Well, being a stealth game, I was fully comfortable sitting in the bush and watching. When guard B came back to the previous meeting point, once again he waved, just like he had when he had been face-to-face with Guard A. After the predetermined period of time, he walked off again. Who the heck was he waving to? My guess was that the "meeting point with wave" was either embedded in the map or, more likely was just part of the patrol pattern of that guard. This is based entirely on the premise that the patrol patterns were timed so that they would meet up. Nice try... but dude looked kinda stupid.

Machine Forgetting

Never mind "machine learning"... how about "machine forgetting?" The premise of a stealth game is that, if you arouse someone's suspicions, they will investigate. However, if you go dancing around in the open and people see you, the gig is probably up. Not so, in Tenchu Z. Apparently, a little-known fact about ninjas is that they possesses the ability to perform the Jedi Mind Trick. (I link this only because I was startled that it had its own Wikipedia entry. Wow.) You can literally mow down half the compound, run around the corner, and all remaining sentient beings will cease to remember your existence. In fact, you can come up just short of killing someone and even he will forget from whence he received his wounds. It's like someone spiked their sake with GHB.

Also, they don't bother to really look for you in more than 2 dimensions. You can leap onto a roof in full view of an entire legion of samurai, and in 60 seconds they won't even consider the idea that you could still be up there. If you crawl under a building in front of everyone, they can have the building surrounded but will refuse to bend over and look under the building. Oh... and then they will leave so you can get out from under the building that they had you completely trapped under. Spectacular.

Now I suppose that some of this may have been a design decision so as to make the game a little more accessible to the "Dragon Ball Z"/"Naruto" crowd, but it is so striking that it is laughable.

Sensory Stimulus?

I'm not sure exactly what they are using for a sensory system. There is a light meter that shows how illumnated you are. That would be an easy coefficient to apply to a detection rate after LOS has been established. You can move quietly which implies that sound transmits - but I'm not sure if it is just a strict radial decay or if there are environmental factors. Of course, rice paper walls transmit sound through them like a drum head. There's some sort of "smell factor" which is probably also just a distance factor as well. I did get a kick out of how the guards are so demonstrative in their sniffing (you can fall into nasty stuff and smell bad until you wash it off)... but the doggies that occasionally appear in the game can't track you in a freakin' bush 2 feet away.

Animation

The combat animation is very schlocky. Maybe I'm just not good at hack and slash games on the console, but it quickly turned into a button mash for me since I wasn't entirely sure that anything I did was more impressive than anything else. The actual contact of a sword stroke was vague and there seemed to be pre-defined kill animations that involved the positioning of both characters. Let's just say you should stick with the stealth because the combat system is less than stellar.

The Solution?

When I started writing this blog, I wanted to make sure that I offered up solutions to problems that I noticed. However, I don't know if that is in order here. One of the major improving points would have been to simply spend more time on it. There are plenty of resources available to get past these issues. Many of them could easily have been addressed.

It is at times like this that I wonder if I can truly blame the AI programmer. Again, as I mentioned before, it may have been a design decision that the experience was not going to be deep and/or challenging. It also may have been a production decision based on time and budget. I can't think that it would have been based on available clock cycles since their graphics don't look like they came close to taxing the 360. So... it either comes down to a low-priority item for them a sub-par effort by an AI guy.

Labels: Tenchu Z

As much as I hate to admit it, there are times when no AI is perfectly OK. I finally got around to playing Portal last week. I figured I would find out what all the fuss was about. Like many people, I thought it was very amusing and disturbingly addicting. It held my attention. It challenged me. It made me mad at times. It made me feel triumphant at others. I was captivated by the characters (such as they are). And then it hit me.

The AI in the game was pretty much minimialistic. The computer AI was entirely scripted, of course. (But the commentary was more than entertaining.) About the only true "AI" in the game sense was the cute little turrets... and even those had about as much AI as could be found 15 to 20 years ago: an obvious state machine (idle, scan, fire, scan, idle), and some ray casting. And yet the cute little buggers were a perfect match for the game in which they were placed. (A first-person version of Peggle? *shrug*)

And that is my observation of the AI of Portal. Almost non-existant... yet perfectly matched to the game. Anything more would have been distracting away from the main charm of the title.

Well done, folks.

Labels: Portal

Ok folks, I know this is getting old. I have been having horrible problems with my ISP since early April. I won't name the ISP yet, but you can look it up for yourself, I suppose. I have been with this company for 6 years and things started fairly well. However, in recent years, especially since a buyout, things have been a little more dicey. Well, this latest issue has to do with a server move gone awry. If the issue persists, I won't hesitate to name them... at about the same time as I go shopping for a new ISP - something I don't want to have to waste time doing.

Because the site has been up and down for 5 weeks, I've been a little hesitant about posting. I have plenty of material I want to put on IA on AI and have been wanting to start putting some new observations on here. I have been assured that the ISP issue will be solved soon (although I was told that over a month ago). However, I think that I may just start writing some of this material anyway. Since I use Blogger, everything is stored on their site first anyway. It wouldn't take me much to republish if I were to lose things.

Anyway, for those of you who have been checking the blogs and finding only errors, I apologize. I appreciate your loyalty nonetheless.

Thank you,

Dave Mark

Labels: IA on AI, web site

Ok... this is kind of a Post-Play'em article. Check out my taped GDC interview with John Abercrombie, AI Lead on Bioshock over at IA on AI.

As I play further into the game, I will eventually post actual play observations. My interview has kinda spoiled the purity of my game experience, though. I know what to look for!

Also, I have posted my notes from Soren Johnson's GDC lecture on the AI of Civ 4. It doesn't get hardly at all into the actual mechanics of what they did (which I plan on doing in my Post-Play'em later) but rather covers how he tried to position the AI as somewhere between "good" (real) and "fun".

Stay tuned for the actual Post-Play'em on that one!

Labels: Bioshock, Civ 4, GDC

A month ago, I mentioned that I was going to be doing analyses of Civ 4 and Bioshock. Well, I have decided to wait until after the GDC next week. The reasons are clear...

1) I will be attending a lecture at GDC by none other than the man behind the AI on Civ 4, Soren Johnson entitled Playing to Lose: AI and "CIVILIZATION". From the description of the session:

Artificial intelligence performs a crucial role for any strategy game, providing a compelling opponent for solo play. While many of the challenges of AI development are technical, there are also significant design challenges as well. Can the AI behave like a human? Should it? Should the game design be adjusted to accommodate the limitations of the AI? Should the AI be exposed to modders? How do we make the AI fun? Should the AI cheat? If so, how much? Do we even want the AI to win? [...snip]

And from Soren's own blog, "Designer Notes" on a post entitled "A Farewell to Civ":

Essentially, I will be talking about the difference between thinking of the AI as the player’s opponent and thinking of it as simply an extension of the core game design (what one might call the difference between “good� AI and “fun� AI). There will also be a long section on AI cheating - the bane of my existence for many years - concerning which type of cheats are acceptable to players and which type are not, using Civ as an extensive case study. Further, I hope to prove that, for Civ at least, there is no such thing as - and never could be - a “fair� difficulty level where the AI is playing the same game as the human. Your mileage , of course, might vary.

Given that I will be getting a peek into what he was actually doing in the AI design, I don't want to stick my neck out and make comments about how wonderful this or that was and find out that it was either unintentional or cheating. That would be embarrassing. Also, I'm hoping to have the opportunity to interview him - or at least hang out with him to some extent. That would provide a lot of great material for a Post-Play'em entry.

2) On a similar note, I received this email a few weeks back under the subject of "Bioshock on Post-Play'em":

Hey Dave,

Cool blog (both of 'em). I'm waiting for the Bioshock review though... curious what you think. :)

See ya at GDC (?)

John Abercrombie (AI Lead on Bioshock)

Oh yeah... that wasn't even remotely intimidating!

I've talked to John a bit since that point... he's actually really cool about the whole thing. It's not like I was planning on ripping his work apart anyway. I'm actually quite impressed with some of the things I've seen in the game so far (I'm still not terribly far in.) We are planning on getting together for a while during GDC. I'm very much looking forward to meeting him and talking shop. In fact, I hope to pick his brain a little on some of the much heralded AI in the game.

So that's what's holding me back on doing those two games right now. I hope to be giving you some juicy tidbits... if not next week during GDC, then possibly the week after I get back. Remember to keep an eye on the IA News blog next week as I report from the GDC and let you know all the nifty stuff I see and do (complete with pictures!).

... if I make it home without going into a coma. What a week GDC is!

Labels: Bioshock, cheating, Civ 4, GDC, John Abercrombie, Soren Johnson