IA Logo


IA Information
Communication

Dave Mark's books

Post-Play'em - Observations on Game AI


Archive for the ‘Observations’ Category

Dragon Age: Origins – Don’t Crowd!

Tuesday, May 25th, 2010

OK, so it has been a little longer than “later this week” for getting to Dragon Age: Origins commentary. I can’t believe I wrote my first look post back in late February. Of course what that really means is that I’m burning some serious GameFly time on this one title… and it’s not like I’m playing it much. My son has managed to get all the way through it, however.

Still, there are some things I noticed as I was going through (which, admittedly, is not all that far yet). One was an odd happening in the Ostagar camp. I was cruising around looking at things and talking to people. As I was standing there talking to Duncan (and a couple of others), a camp soldier of some sort came and stood near us. From the looks of it, he was supposed to be dealing with another person there, if I recall correctly. This didn’t really catch my notice until a 2nd soldier came up and attempted to stand in the same spot and talk to the same person. They jostled each other for a bit until the first one walked away – apparently on a random patrol route.

…a 2nd soldier came up and attempted to stand in the same spot…

I believe that it was the random patrol routes that caused this issue in the first place. My guess is that the guard logic simply selects a new destination and heads out in that direction. If, for some reason, there is someone already there, it doesn’t detect this or care… it simply continues to try to get to the node.

There are a few ways to either avoid that or fix it. First, the goal nodes could be reserved and released as they are selected and then left. The problem with this solution is that a goal node would be “out of commission” from the moment someone reserved it to the time they left it. If they were coming from all the way across the map, that node would be off the market for quite some time without actually being used. Additionally, it would prevent someone from heading in that direction until the original occupant actually left.

A lot of work to make the camp “feel alive” went down the drain…

A more realistic solution would be to simply be aware of other people. If there is someone on your “spot”, don’t actually try to move onto it. This could be done by simply stopping short of your intended goal (e.g. stand next to him) or by using some local avoidance. The later is probably better because collision avoidance should be part of the movement scheme anyway for other reasons.

Anyway, the result of this was that it was a jarring cancellation of my suspension of disbelief. Because it was right next to me and in view, I couldn’t help but notice that these two dolts were climbing all over each other. A lot of work to make the camp “feel alive” went down the drain right there.

Dragon Age: Origins – First Look

Monday, February 22nd, 2010

Just sat down with Dragon Age: Origin for a while. I know I won’t get too far into it anytime soon because, for a Bioware game, that usually means a commitment of a few months. I plan on blasting through more soon, but the 360 is on the same 43″ HDTV that the wife wants to watch Olympic stuff on. (I can’t begrudge her that since she usually doesn’t watch enough TV to get in the way of my gaming.)

To give a frame of reference of how far I am, I started as a City Elf and am only just about ready to roll out of town with Duncan. That has, at least, given me plenty of opportunity to go through both peaceful and combative encounters. Also, I haven’t yet dealt with the NPC behavior customization. I imagine that will be more important as I go foward, but for now I just wanted to live by the defaults.
Well Lookie Here!
One of the first things I noticed was when I was in a conversation. While I like fact that people’s eyes move and blink, I would like to see a little more movement. There is so much that can be said by breaking of eye contact, turning the head while still speaking, etc. I have written about this here and there before (and really should write a formal article about it). The point being, what they have done is a start, but it isn’t enough to really sell the character. As an example of dialog scenes that are well done, I point you to Assassin’s Creed (the original at least… haven’t seen AC2 yet). Previously, I wrote about how I liked that, in Assassin’s Creed, not only could you walk around during conversations, but that the NPCs did as well. They looked down, away, etc. I would like to see more of this. The walking around isn’t even quite as important as the head and eye control. Some of those can even be randomized — especially with parameters — so it’s not like it would take a lot of work or resources.

On the subject of head movement, however, one thing I noticed the first time that I was in a conversation with two people was that their head turns are NOT animated by hand but are automated. The reason I know this is that there is a very distinct start and end to the turn and that the turn rate is entirely constant during the whole turn. Put another way, if someone turned from looking at me to the person standing beside them, that 90° turn would go from a rotation rate of 0 straight to n, rotate that 90°, then change rate from n to 0 again. The rate, n, was always the same throughout one turn and on every turn. The overall effect made it look like one of those audio-animatronic characters in a Disneyworld exhibit. It was very mechanical-looking.
While I like the idea behind the technique, I believe a better way would have been to randomize the rate, a rate of change into the turn, and a rate of change out of the turn. This not only changes things up between one turn and the next, but also smooths out the starts and stops so it doesn’t look like little servo motors kicking in.
… one of those audio-animatronic characters in a Disneyworld exhibit.
Also, you don’t always have to look directly at someone. If someone standing next to you is speaking, you can turn your head part of the way and do the rest with your eyes. In fact, it is very common for humans to “split the difference” and look somewhere between the two speakers in that arrangement. Toss in the occasional look at other objects of interest in the environment (especially if you’re nervous, wary, etc.) and you can really sell a conversation without a lot of extra work.
Don’t Mind Me
She never acknowledged that I was even there.
While I appreciate that not every denizen of a place should attack you, I would at least like them to acknowledge my existence. For example, I was a little startled when I was storming the castle. In a couple of the rooms, I came upon a woman scrubbing the floor. She didn’t look up when I entered (if she was a servant, shouldn’t she care to see if it is a boss?), she didn’t look up at I moved around, she didn’t look up as I stood with my boots under her nose. She never acknowledged that I was even there. She didn’t do anything other than scrub the floor. It was a little startling, especially when everyone else in the place (friend or foe) recognized that, as an armed elf, I was seriously out of place. (Incidentally, I got a kick out of the fact that this matched up nicely with the theme of AIGameDev‘s AI Marmelade – their twist on the Global Game Jam. Their coverage of it was sub-titled “on little old cleaning ladies in stealth games.”)
I admit that this is likely a content issue. Developers would love to add more background characters to an area, but then you run into the issue of having them react in meaningful ways. Also, if those reactions are going to involve custom animation or sound, the expense goes up significantly. It would be nice to have a general list of generalized actions and interactions, however. Put people in there moving from place to place, carrying things, tending things, etc. When I come in, at least have them look at me. If I try to engage them, make them politely dismiss me. If I do something flashy like attack people, make them run. That much, at least, puts a little life into the place. Oh well… no one can ever say Bioware skimps on content. They just put it into length of the experience rather than the depth of it, I suppose.
Combat AI – So Far…
I was a little wary going into this first play session because someone I trust on AI commented that he was frustrated with his party members. As I said at the top, I haven’t gotten too deeply into the game and haven’t messed with the customization yet. However, there was nothing that I saw yet that was really “pants-on-head retarded.” I was a fighter as was my buddy. He attacked when I did or when we were attacked. I was too busy trying to do my own gig to see if he used a healing option when he should have. I don’t think he did because he “died” a couple of times during our great castle adventure. I didn’t think to give him a ranged weapon to see if he would switch at appropriate times, though. And now, of course, he is no longer in my party (taking some cool gear into the abyss of retirement with him). My next play session will have me leaving town with Duncan and likely teaming up with some dudes. We’ll see how things go then.
… it looked a lot like a tool that an AI programmer would make for a designer.
I only briefly looked at the customization system. From what I could tell, it looked interesting if you are an AI programmer or a designer. In fact, it looked a lot like a tool that an AI programmer would make for a designer. I would lay money that it’s origin is not too far from that. I can see how it would tend to quell the inevitable gamer uprising that would like more control of the autonomy of their party-members (is there a contradiction in there somewhere?). However, it was said by a few people that you actually have to tweak this system by hand to get people to work together properly. I really don’t like this idea. In my opinion, if it doesn’t work intelligently with the default settings, there is something wrong.
From a technical standpoint, the system looks like it is a parameterized rule-based system of some sort. I’ll have to play with it… for all I know, it is tweaking a behavior tree behind the scenes. Much of my conclusion on what is going on would be based on whether you can sort your rules in a particular order of consideration. Like I said, I only just glanced at it. More on this after I play. In the mean time, I refuse to look up any technical documentation on it just to see if I can figure it out on my own.
The enemies were pretty much standard “fight to the death” fare so far. They were all castle guards and punks, though. That would be right up their alley. I’ll have to see what other types of enemies offer later on.
Anyway, despite their similarities in production, the game is much more enjoyable to me than Mass Effect was — at least for now. I’d be pleased if that stayed the case.
Definitely keep an eye on the rss feed here. I’ll be writing more about this game later in the week.

Brütal Legend: First Look

Sunday, February 14th, 2010

Next on the pre-GDC flush of my GameFly queue is the metal-themed game, Brütal Legend from Double Fine. This one has a little more urgency in it because my friend and AI Game Programmers Guild colleague, Tara Teich, did a lot of the AI for it. She is going to be explaining some of the challenges she faced in her lecture at the 2010 AI Summit at GDC. Specifically, she is going to be talking about marrying some facets of an RTS game (always a little more difficult on a console) with those of a typical brawler game.

Anyway, from a purely thematic standpoint, I have to find myself laughing rather often. It must have taken quite some time for the design team to make a list of every single hard rock and metal sterotype… or should I say stërëötÿpë… and figure out a way to insert it into the game. Anyway… that’s design, not AI, but it was worth noting. Very amusing game so far.

Anyway, from an AI-focussed view, it is certainly in a different ballpark than some of the other games I have been reviewing on here. RTS games like Company of Heroes, RPGs with heavy AI components such as Fable 2, and animation masterpieces like Assassin’s Creed are on a completely different wavelength than something like Brütal Legend. It’s not meant to be complicated, intense or clever. Instead, it’s meant to be accessible.

Give it Away, Give it Away, Give it Away Now…

One thing that I noticed just before I sat down here at the computer was the “tells” during a “boss battle” with a giant metal spider. As is typical in boss battles, the enemy will have a certain list of attacks that it performs on you. Each one of those attacks is preceded by a short preparatory move so that you know it is coming. There’s not a lot of subtlety or guile in boss battle “tells”. That’s the whole point. The other aspect of having tells is that you can pretty much string together attacks in any random order because the only thing the player is looking for is tell -> attack. On the other hand, I thought I detected a distinct pattern of some of the attacks. For those of you who have fought that spider, it seemed like there was a sequence of
  1. release the little spiders
  2. shoot the splashy stuff
  3. the engine gets exposed
It happened enough times that I could eventually put together the sequence of dodging the splashy stuff, tossing off the little spiders, and then shocking the engine.
To be honest, though, I really don’t like this type of combat. I’m not a puzzle-solving kind of gamer. I’m more of an NP-rediculous, react, plan, solve, be creative with how to ass kick, kind of guy. However, that’s a legit design decision for the majority of the gaming public and I’m cool with that.
All Together…

I can see where Tara is going with her idea of merging RTS and brawler features, though. When you start fighting along with the headbangers (some of whom I swear I went to college with), the game introduces you to a few rudimentary commands such as follow me, stay here, attack that, etc. Those aren’t so intriguing from an AI standpoint. A little further on, however, you are introduced to the idea of the “mosh pit” – another wonderful twist on a metal cliché. When you are surrounded by 6 of the headbangers and they form the moving circle around you, it is amusing. When you actually enter combat with this ring of cranium-wielding warriors, it becomes interesting.
I wish I had video of these battles so I could slow it down. I want to see how much intelligence is going on with their respective target selection. It seems like they are doing more than just hitting anything that comes near them. They do go out and find a near-by target, I think. However, do they divvy those targets up or is there occasionally some inefficient overlap where 2 ‘bangers go after the same guy? Dunno… This would have to be done with some sort of sorting and semaphore system — in layman’s terms, each one saying “I got this guy here… find your own”. I simply don’t know if that would be worth going through the trouble, however.

The animation during the cutscenes is nice. The faces (especially Jack/Eddy) are expressive in an amusing way. I have to assume that is hand-done, however. Not much of an AI-fest there.
The rest of the animation is rather typical. Again, they aren’t trying to be Assassin’s Creed here. I’m OK with that.
I think what I’m looking forward to most as I move through the game is more of the group scenes. I want to see how the groups of headbangers (or whomever) deal with larger groups of the enemies. After all, that’s what Tara identified as a challenge of sorts.
In the mean time, I’m just gonna rock out!

Mass Effect: First Look

Friday, January 29th, 2010

I’ve had my copy of Mass Effect (yes, the original) from GameFly for a month or so now. My son played it for a few straight weekends when he was visiting and finally finished it. Seeing how long it took him to go through has convinced me that I do not have the time to ever complete the game. However, I did want to get a feel for what it was like specifically for reference purposes. Here’s a few of my first impressions.

Good Dialog Animation

One thing I noticed that was rather pleasant was that the cut scene dialog animation was reasonably well done. This is even more impressive since there are at least a dozen races that I have encountered so far and all of them look believable when they are speaking. I happen to have a soft spot for ol’ Urdnot Wrex who looks particularly compelling when he speaks. Kudos to BioWare for pulling that off well.

Fixed Cut Scenes
On a down side of that is the fact that I now feel really rooted to the ground during those dialogs. Much of this is by an unfair comparison, however. After playing Assassin’s Creed where I could wander around aimlessly during dialogs, I found myself a little restrained during the Mass Effect ones (of which there are plenty). Which brings me to another point…

Odd Disconnects
Having been a veteran of Neverwinter Nights, I am well familiar with the extent that BioWare can take their contextual dialog trees. While I agree that this is still largely a necessary evil in RPG games, there are times when I am a little alarmed by a continuity disconnect.
For example, upon arriving in Noveria, I had a pleasant chat with the lady Gianna. She tells me upstairs at the security station to come see her to have an appointment with Anoleis. It took me less than a minute to get down to her office where she greeted me with the question, “What do you want?” It was rather startling to have just left her and have her forget that she told me to come ask her something specific. Of course, this is something that can be chalked up in part to poor writing. On the other hand, this is also something that could have been added as a trigger flag in the dialog tree itself. That is, if the player gets to you quickly, acknowledge it and say something appropriate. In this case, it would have been “Ah, you are here. Let me announce you to Anoleis.”
On the other hand, the in-dialog flags seem to be well done. Often, they will remember that I have asked about one topic in another branch of the tree entirely. That is well done. Of course, I was tickled when one character told me off by saying we have already discussed something. On the other hand, I can see how that would be annoying if you were distracted by something and didn’t hear what was said.
Another peculiar interaction was when Gianna met me outside a room after I had finished a combat sequence. (I believe it was outside that one dude’s office.) She told me to talk to her in the hotel bar before I spoke to the guy who sent me on the mission. Uh… OK. The problem was, as soon as the cutscene was over, she was gone. We didn’t get to see her walking away or going to the bar, etc. Not having anything else to do, I went to the bar and found her already there (she’s quick!). Again, this effect is a by-product of having the cutscenes be somewhat de-coupled from the actual live action gameplay. It’s mildly annoying.
Not much of that has to do with AI, however. This next bit does.
Combat AI
In a few of the combats that I have been in, I’ve noticed a peculiar combination of tactics. While I praise the design that puts some enemies behind cover for a while. It seems like they also leave cover for no reason, walk some pre-programmed path while still firing at me, then return to cover. If that doesn’t smack of a shooting gallery, I don’t know what does. Additionally, there have been times when an enemy inexplicably leaves cover and runs right up to me in the open. It seems to be a design decision to “mix things up” however. While mixing things up is fine, it doesn’t really make a lot of sense from a combat standpoint. Because of that, it makes the enemy look dumb. If the enemy looks dumb, people think the AI is dumb. It is unwise to intentionally write something into your enemy AI that people will perceive as being broken – either technically or in the “brain” of the enemy.
All in all, the AI seems to alternate between overly scripted or a sequence of randomly strung together actions. There isn’t that cohesive combat flow that I experience in the likes of Halo 3, Gears of War 2, or F.E.A.R. Interestingly, this makes the battles almost as mundane as the incessant walking (jogging) and driving that you have to do in the game. Where I would hope to have the proverbial minutes of terror to break up the hours of boredom, I don’t even get a rise out of the combat. That’s disappointing.
Anyway, while I don’t plan on finishing the game, I will put a few more hours into it and see if I notice anything else.

Assassin’s Creed: First Look

Sunday, April 26th, 2009

In my latest episode of “finally got around to playing”, I have had a chance to mess with Assassin’s Creed (on X360). As with most people, I was immediately impressed by how visually attractive the game is. However, that has usually been a warning bell in the past. A lot of time “pretty game” has tended to also portend “stupid AI”. This doesn’t seem to be the case with AC.

While this isn’t normally my strong suit, I have to say that the animation model in the game is very well done. Even without the climbing and hoping and dodging, there is a lot of detail that made for convincing depth in the characters. Even just running forward and then rapidly changing to run the other direction prompts a foot plant and skid animation that is really kind of cool. I also like the fact that the transitions between animations are very smooth. Even just something as simple as changing from a walk to run and back to a walk (even on horseback) exposes a gradient of speed that does not have the hard-edged state change feel.

Look at me when I’m talkin’ to ya!

I also like how you can move around during the (long) dialog scenes. You don’t have to, but you can. In fact, I found myself wanting to pace during these conversations because it made it more realistic. Additionally, when your character says something while he is facing away from the listener, he will turn slightly towards him… not to directly face him, but to talk in his general direction. Think about it… don’t we all do this? How often do we actually look directly at the person we are talking to? It’s a nice touch with the animation that makes those plentiful dialog exchanges more livable.

Running, Jumping, and Climbing on Things

It goes without saying that the advanced animations are very well done. The climbing and running and jumping business is ridiculously well done. There are the occasional quirks but those are more of a problem with the control scheme (on the 360) than anything else. I especially like when I get too close to an edge and my dude has to fight to keep his balance.

Excuse me. Pardon me. Move, damnit!

There are ways that they incorporated this into the game design other than all of the building stuff, however. It was a very nice touch to have the character stagger or even fall when he runs into people. That makes the chase scenes through cities very realistic in that you do have to pay a little attention to where everyone is.

Of course, in order to utilize that mechanic, you have to pack the streets full of people going about their business. This was done very well. There are places where it is next to impossible to run through simply because of the press of people. Even walking through them can get annoying. I haven’t bothered to simply watch people to see where they are going, but you don’t get that initial impression of “random walk” that you get from a lot of other games. (One recent transgressor in this effort was when I was playing Oblivion where every person in the city just broadcasted “I am so lost!” I will write up my observations on Oblivion later.)

An even better touch is how the people react to your passing… not just physically, but verbally. If you bump into one of those jar-toting ladies and get them to drop their burden, they will give you a little lip. The same can be said for running into a dude when you are on a horse. I found myself being more careful moving through people just to avoid what should be relatively innocuous confrontations.

The agents in the game, be they friend or foe, do have a pretty obvious state-based behavior pattern. It works for this game, however. I also haven’t seen any situations where the FSM is stuck on stupid. The game mechanic has enough depth that the predictability of the guards is acceptable.

Now serving #43

I guess the only thing I can fault (although it still works well) is the “ninja fight” rules where the enemies tend to come at you one at a time. They do take turns, however, rather than waiting for the one fighting you to die before the next steps in. Again, this was matched well with the game mechanic of being able to grab people and throw them away. When you toss one dude away, his buddy will step right in. It does make the fight more manageable, however. On the other hand, there have been times when I have had more than one guy beating on me at the same time. I haven’t figured out what the difference is in those scenarios, however.

All in all, the game looks pretty good from an AI standpoint. I say that based on the fact that I haven’t noticed anything horrible about it. That’s usually a sign that things are working well. Figure that AI should be like umpires or referees in a sports game. They are necessary for the game to work smoothly, but you shouldn’t really notice that they are there.

I’m returning AC to GameFly tomorrow (although I will probably buy it because my kids are addicted to it) so it will be a bit before I follow up on this post. You can check to see if I have written anything else by clicking the Assassin’s Creed tag below.

Make sure you subscribe to the Post-Play’em feed to see more reviews and analysis.

Interview with AIGameDev re Left 4 Dead

Wednesday, April 15th, 2009

Back on April 5th, Alex Champandard of AIGameDev interviewed me for about 90 minutes for the Members portion of his site. Our topic was how to use behavioral mathematics (such as I cover in my book) to improve the bots in Left 4 Dead. We cover a lot of interesting information in the interview. Some of the examples refer to things I covered in my columns here on the AI in the game.

He has it posted in audio and video formats (although with me rocking back and forth in my office chair, I look like I’m autistic!). I seriously advise that you check it out. (You will need to have access to the members area to view it.) If you are already a member of AIGameDev, you can find the interview here:

Fable 2: First Look

Sunday, March 8th, 2009

Continuing with my pre-GDC blitz of “must at least look at” games, I have just putzed around with Fable 2 for about 90 minutes. I had a look at some of this material back at the 2008 GDC when Peter Molyneux was going through his pre-release hype. (Isn’t he always?) Therefore, I knew some of the things to look for.

Most importantly, on the AI front, is the inclusion of the almost legendary “dog” AI. To hear Peter talk, you would have thought this game was a bigger and better “Nintendogs” game… that the entire purpose of buying it was to play with your doggie and bond with him. While that isn’t exactly the case, I have to admit that the dog is a good point of interest. The dog certainly is convincing in many ways.

My Dog Runs Rings around Me!

I think one of the things that was startling to me was how it moves in a general area around you. Most companion AI tends to lag behind you. For example, my recent mucking about with the companion AI of Left 4 Dead has me convinced that I am the only person in the entire world with any initiative. This is obviously a logistic issue because very rarely can the AI know where you want to go or when. This is sometimes mitigated in linear games where there is only one place to go. In my short experience with Gears of War 2 today, I saw that exact phenomenon. My companions were able to move ahead of me and take up positions specifically because there was no other way to go.

In Fable 2 this is done via the “breadcrumbs” trail. Despite being far more “open world” than other games, if you have selected (or the game has selected) a destination, by extension, the dog knows where you are headed. Of course, if you turn around and backtrack or go off to one side for some reason, the dog has to react and come back to you… but this is what happens in real life anyway.

The result of all this is that the dog will playfully romp or explore ahead, behind, of off to one side or the other in a general “halo” around you. If you stop traveling for a period of time, he will come back and see what’s up. If you stand still for very long, he may even lie down for a bit… all the while keeping an expectant eye on you as if to say “now what?” It’s all very convincing.

I really noticed one particular aspect of the dog’s animation after I put the controller down and switched off the 360. I went to go feed our own dogs and, as I was walking from the food bin to the bowl, one of our dogs was walking a few feet ahead of me. However, he had his head turned slightly back toward me, keeping an excited eye on me and the cup of food that I was carrying. He did that very dog-like routine of glancing forward and then back at me over and over all the way to his bowl. It struck me that this is exactly what the dog in Fable 2 was doing as I walked. As he would criss-cross in front of me, he would keep glancing back as if to make sure that I was coming along with him. It was this sort of attention to detail both on the behavior and the animation AI that really sold me on this dog. I’m looking forward to experimenting more with it soon.

Look at Me When I’m Talking to Ya!

Interestingly, there were times with the villager AI that I felt that the eye-contact issue was the problem rather than a feature. I’m not talking about how, while in conversation, people will glance away or past you. This was a problem with where they were facing in general. If they started their spiel while I was in one place, and then I moved to one side or the other, they would continue to face the spot where I was. Only after a moment (usually after finishing a line of dialog), would they turn to face me again. It was all rather disconcerting. Compare this to how well games like Half Life 2 continued to address you throughout a conversation… even to the point of turning and walking backwards if necessary.

Dialog Pauses

Another problem I had with the villager AI was how many of the scripted dialogs had very unnatural pauses between lines. There was an awkward silence between many of their sentences that left me wondering for a moment if they were finished or not. It was one thing when it was in response to something I had selected. However, when they paused in conversation with each other, it was odd. When they paused between their own lines, it was horrific and very distracting. I have to imagine that this is because each line of dialog needed to be loaded and accessed separately, but I can’t see why this would be a problem.

Both the facing issue and the dialog pause issue may be related to the same root cause, however. It may be a result of waiting for an associated animation to finish and report back that it is done. If a line of dialog (and the code to “face the player”) are associated with a particular animation, they would each have to wait for the other to finish before they both advanced to the next segment. If the animation finishes first, it isn’t as tragic because the animation can sit in idle for that extra second. However, if the voice finishes first, the next line must wait until the animation is done — causing the unnatural pause. This is just speculation on my part for the moment. I figure that if I analyze it a little further I can make the determination down the road.

Individual Individuals

One thing that jumped out at me during the initial city quests was how the group of kids all reacted slightly different to my various gestures, poses, and flatulation. I would get more “love points” (or whatever) from some than I would from others in the group. Upon a little examination, I found that each person had their own likes and dislikes — that is, things that they were more impressed by or didn’t like. It’s one thing to have different “respect ratings” from different people. It’s quite another to have different models of what causes respect on an individual basis.

I found this rather amusing since I am doing a co-lecture on this very subject at GDC in a few weeks. (“Breaking the Cookie Cutter: Modeling Individual Personality, Mood, and Emotion in Characters“) It’s something I would like to see more of in games in the future — although maybe not in quite as transparent a fashion as what appeared on-screen in Fable 2.

Will You Treat Me Different When I’m Famous?

I think it will remain to be seen what happens when I’m more renowned than I am so early in the game. In the original Fable, it got rather annoying that everyone, everywhere wouldn’t shut up about you. The comments that they heaped upon you were not as many in number as there needed to be. (You can only hear “chicken chaser” so many times before you want to crack someone’s head.) With a nod to my friend and colleague, Adam Russell, who did the villager AI for Fable, that isn’t an AI problem as much as it is a content problem. (This is another bit that I will bring up at the AI Summit panel, “Characters Welcome: Next Steps Towards Human AI“… it doesn’t matter how many decisions our AI can generate if we don’t have enough art and sound assets to express it.)

Anyway, this is a bit long for a first look. I will tag on some more as I experience more of the game. On the other hand, I will be shipping this back to GameFly in the next day or so. I need to check out a couple more titles before GDC in a couple of weeks.

If you are just jumping into this one article, make sure you click the tag(s) below to see if I have written anything else about Fable 2.

Gears of War 2: First Look

Sunday, March 8th, 2009

In preparation for the AI Summit that I am helping put on at the 2009 Game Developers Conference, I am rapidly cranking through some of the key games of the year. So, I signed up for GameFly just so I could putz with some games in the short term. I will likely buy some of these games down the road, but the research budget for IA doesn’t cover spending $300 on games in only a few weeks!

Well, the first thing in my queue (along with Fable 2… check back later for that) was Gears of War 2. I had seen a number of the reviews in various places and I was impressed by not only what I saw but by what people were saying about it. Despite having Gears 1 sitting here, I had never really played it. (My son had.) So really, I had no idea what I was getting into.

Ok, wow.

Obviously, it is a very good looking game… but that’s not what this column is about. After watching Yahtzee’s take on the game, I was also fully prepared for plenty of “chest high walls”. Of course, there’s good reason for that given that the cover fire system is an integral part of the game. On the other hand, I have not seen the poor AI quirks that Yahtzee cracks on the same review. (Although I suppose referring to the generally satirical and sarcastic Zero Punctuation blurbs as “reviews” is a bit of a stretch now, isn’t it?)

So far the AI seems pretty solid. Now note that I have only played the opening level up to just past the epic speech (<- unintentional pun for those of you who actually pay attention to the names of the game studios who crank out your entertainment products) so I haven't experienced too much of it. However, what I have seen has been pretty decent for a shooter. The enemies are frustratingly adept at using cover. I have often found myself flanking them just so I can get a shot around whatever “chest high wall”-like object they are behind. What’s more, I have noticed that they will shoot from around different sides of the object. If the baddie is behind a desk, he may pop over it or around the side. This is a nice touch of realism that steps away from the typical method of 1-1 relationships of designer-tagged points. That is, there is no “and at this point, the AI can shoot over the object.” There seems to be simply “here’s a hiding spot… let him do what he needs to do.”

My allies seem to be pretty proficient at using the cover as well. Of course, I haven’t been paying too much attention to what they are doing since I have been concentrating more on saving my own ass. (Nota bene, I’m playing on the hard difficulty level.) However, as we move from battle to battle, I do notice that they are very conscientious of taking cover as we go… even when they are simply waiting for me to catch up.

All of this cover-taking is very refreshing in a shooter. I have (for 15 years?) been so tired of enemies (and allies) that simply stand out in the open and either wait to get shot or are so invincible that cover is unnecessary. (Yahtzee suggests this is possible in GoW2, but maybe he was on a different difficulty level than I am.)

For the most part, the animation seems clean. The transitions are pretty decent and any quirks seem to be more a result of the control system than the animation. That’s a hard problem to solve, so I don’t bitch about it too much. A better example is watching the animation of the AI characters rather than of myself. Everything seems smooth as they move, duck, fire, etc. I will pay more attention to that as I go.

I have yet to play enough to see how much of the enemy combat events are scripted and how many are dynamic. For example, early on the Locusts in the hospital are retreating… but that is obviously scripted as I have played through it three times (twice by myself and once in co-op with my son). I understand that. However, as I play on, I would like to see if there are places where the enemy retreats simply because I’m kicking his ass. I saw a lot of this in Halo 3, for example, which was controlled by Damian Isla and Max Dyckhoff’s battle management system. Given the impressive use of cover in Gears, the inclusion of a good fall back or retreat system would be cool. We’ll see.

That about covers it for the moment. More later. If you are jumping into this article, remember to check the Gears tag below to see if I have written anything else about this game.

Left 4 Dead: First Look

Monday, February 23rd, 2009

Ok… half price weekend on Steam finally got me into Left 4 Dead. After watching all my TF2 buddies drifting away to this mysterious “other game”, I needed to jump in and take a look. Also, since it will likely be the buzz of GDC next month, I figured I had better have an idea of what it looked and felt like.

I have to admit that it’s a pretty groovy game. All the stuff we have heard so far is correct. The online, team play is cool. It’s so much better than most team shooters in that it seriously punishes you for separating from your cohorts too much. Also, because there is such a significantly different array of tactics that are necessary for playing as the infected, the versus mode is almost like having a second game. But that’s not what this column is about…

The big AI pull on Left 4 Dead is the “AI Director” that we have all heard so much about. In an interview with Edge Online, Valve’s Gabe Newell talks about all the nifty stuff they tried to take into account. Wikipedia even touches on the AI Director. It’s no secret that this tech was a big deal.

When I finally got to playing it, I was very impressed with it myself. Having played through some of the levels more than once (like No Mercy, for example), I am well aware that I don’t know where anything is going to be next. Compare that to other games where the 2nd time through you already have an idea of what is coming next… by the 3rd or 4th time, you have it down. I don’t like that amount of rigid predictability. With L4D, I have been on my toes at all times.

It does seem like it does a decent job of balancing the flow of the game. There are plenty of times when I’m “on the edge”. Compare this to the rubber banding I suspected in Doom 3 where it just seemed that the lower I got on health, the less damage the enemy did. The result was an (almost) asymptotic approach to 0 health. Exciting? A little. Contrived? Definitely. With L4D, this feeling is much more natural in that it is adjust the pacing of the enemies themselves rather than adjusting the abilities they present. Rather than the confusion of “why is this horrible monster doing very little damage now that I’m almost dead?”, I find myself saying “thank God they aren’t coming after us just now… I need to heal up a little!” It’s a subtle difference, but it is there.

That’s not to say that the game is always winnable in true rubber band fashion. On my first day of play, three friends and I played that last rooftop level of “No Mercy” about 8 times and kept coming up just short. It was exciting each time. Finally, we beat it by only barely dragging our asses into the chopper. Quite the getaway! As we reflected on what had happened (the game was new for all of us), I noted that every single time was different. Different monster placement, different ammo placement, different items, different pacing. We couldn’t do the same thing each time because the computer wasn’t doing the same thing. One time we used gas cans to light fires. The next time, I went looking for the gas cans… only to find that they weren’t there (they were across the level). The next time, there were no gas cans at all… just more propane tanks — which meant a different strategy entirely.

What I have found interesting is, while playing the infected (which I am having trouble getting the hang of), I can watch the other zombies “pop in” as they spawn. It’s kinda fun to see them do that. Oddly, I feel a strange kinship with them at that point. (“Yeah, right here buddy! We’re gonna get ‘em from this closet, right dude? Right? Hey… pay attention to me!”)

The other thing I get to watch as the infected is how their “idle” behaviors work. There are quite a few of them and they blend well. Admittedly, by their nature, zombies don’t have to be terribly engaging, but it is a nice touch to come around a corner or see a group far off actually doing stuff. Sometimes, I feel that the sensory distance is a little short, however. If a little beepy grenade gets every zombie in the same zip code to freak out, why doesn’t my shotgun wake them all out of their staggering stupor as well? Again, people just don’t model the sense of hearing well in games. *sigh*

The AI of your counterparts is pretty decent, for the most part. I’ve seen a couple of odd glitches, however. Therefore, I think I’m going to make that a separate post so I can possibly post some FRAPS-caps of them in action.

(As always, make sure you check the tags below to see what else I may have written about this game.)

Half Life 2: Paying Attention to Me

Tuesday, February 10th, 2009

When I posted my first observation on Half Life 2, “Movement on Rails” the other day my colleague, William van der Sterren commented that one of the cool things that they did in HL2 was making the NPCs acknowledge the player’s position during conversations. While I certainly agreed at the time, I thought this was limited to eye contact and head position. That was just the beginning. I had not experienced the full depth of what they had done in the game.

Last night as I was playing some more, I had some of the extended conversations at Black Mesa East. As Dr. Mossman was walking me through the lab, I was surprised to not only see her turning her head, but even walking backwards (convincingly well) at times so that she could continue to face me. I’m tempted to go through that section again just to mess with her. If I keep moving, does she keep changing?


Anyone who has coached kids playing baseball has probably taught the drill of how to watch the ball as you are running backwards. Part of that drill is to change sides without turning your head. That is, looking over your left shoulder, then turning your lower body to run with the other shoulder leading so that you are now looking over your right shoulder. I think it would be interesting to watch the NPCs in HL2 react to that sort of situation.

All in all, I agree with William that it was a new point of immersion for a game NPC. More specifically, it worked to not break the suspension of disbelief simply because it looked natural.

Monlogue Breaks

On the other hand, there were awkward pauses in the monologues of the various characters. Sometimes, I figured that they were waiting for me to cross an invisible trigger threshold. That is, as they entered a room, they waited for me to cross through the doorway that they were then going to close behind me. However, the next line of monologue was put into the same queue as the actions such as closing the door. Therefore, they could not proceed with their spiel until such time as I allowed them to close the door. If I had not moved, they would never have continued.

A solution for this would be to have a separate queue for the speaking and the actions. However, the speaking could be superseded by ad hoc lines such as, “Come on through the door so I can close it behind us.” and then continuing on with the monologue. This shouldn’t be too difficult to do with a priority-based system. The insertion of the vocal line “Come on through…” would be a higher priority than the other lines. As each normal line finishes, it triggers the insertion of the subsequent line into the queue with the appropriate priority. If there is nothing else more pressing, it would chain right on the end as per usual.

One of the effects you can pull off with this method is reaction-based stuff. For example, I was dying to fire my pistol into the ceiling during some of the speeches and conversations. Would they have reacted? I don’t know about HL2, but in other games, probably not. However, a priority-based system would override whatever sequence is being dictated with “What the hell are you doing?”, a few follow-ups about shooting weapons in the house (“You’ll put your eye out, kid!”), and the revert back to the regularly scheduled monologue.

Another effect would be acknowledging random people walking by. For example, during the hallway monologue, Dr. Judy could have received an event that a colleague was approaching coming the opposite direction. She could have inserted a slightly higher priority event to say “Hi” to the person in between lines of her monologue. She would say “Hi” at a break between lines and then go back to what she was talking about. Sure, there are caveats that you have to look for, but the inclusion of simple mechanisms like this work in a similar fashion to the head-turning one. They look natural and therefore feel natural to us.

(Remember to check the other Post-Play’em observations on Half Life 2.)

Add to Google Reader or Homepage




Content 2002-2018 by Intrinsic Algorithm L.L.C.

OGDA