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Posts Tagged ‘Gears of War 2’

Gears of War 2: Cover vs. Running Around

Sunday, June 12th, 2011

The recent E3 (2011) reminded me that it was time to catch up on some games. Additionally, it reminded me that I really want to comment on the AI of the games that I play—something that I haven’t been doing as much of lately… at least not on here. So, after having not touched it for a while (2 years!), I picked up my copy of Gears of War 2. (Thanks again to Epic AI Programmer, Matt Tonks, for providing me with a copy of the game.)

Peek-a-boo

The AI in Gears 2 actually uses cover in a reasonably intelligent manner.

It took me a while to get back into the groove of the control system—most notably how to use their cover system. At the time, using cover that way was a fairly fresh idea. It has been utilized in plenty more games since then, of course. Even better was how the AI was using cover. Unlike other games that I have played where the AI either subscribes to the “Doom model” of standing out in the open, or half-heartedly takes cover, the AI in Gears 2 actually uses cover in a reasonably intelligent manner.

For example, compared to how the AI in Mass Effect used cover as two ends of a shooting gallery path, the AI in Gears 2 seems to take advantageous cover and keep it. This really adds some nice depth to the game in that, often, the only way to solve the resulting stalemate is to flank them so that their cover is less useful.

I can’t just sit there and play Whack-a-Mole.

Their “pop-outs” to fire on me are quite unpredictable which is frustrating (in a good way). Additionally, if the cover is long enough for them to move behind it, they seem to do so. Again, this is one of those things that, unless I was running a video recording, it would really be hard to discern in the middle of a firefight. What I do know, is that I can’t just sit there and play Whack-a-Mole with someone who is in cover—waiting with my cursor positioned perfectly so that when they pop up, I can pop them. That has always been a tactic that my slow thumbs relished because it was so simple to defeat. If the enemies are moving and popping up at unpredictable intervals, I either can’t anticipate where or when they will do so, or I simply get anxious and move on to another target that is visible.

As a follow -up to that last point, it is often hard to switch from one target to another in time because their exposure is so limited. They truly do only “pop out” rather than “come out and remain a really obvious, easy-to-hit target.” All of this serves to create a very frenetic atmosphere in the combat… even the “trench warfare” combat that could normally get pretty stale.

Round-and-Round

Unfortunately, there is some issue I take with the combat AI. Sometimes, both friend and foe seem to get into a mode where they are dashing around in odd ways. This seems related both to target selection (and by this I mean not just who to shoot but where to go) and idle situation positioning. In the former, it seems similar to what I experienced with Dragon Age: Origins. In that case, enemies would run past one of my allies—completely ignoring them—in order to get to me.

It simply doesn’t make tactical sense to leave your group like that.

In this situation, it isn’t necessarily limited to the enemy having an unhealthy preoccupation with me. My allies will run off into combat way out in front of what are obviously established lines. This surprises me quite a bit when I’m looking way downrange from our location (even sniping) and suddenly see one of my allies appear in my scope. It’s not as if I am holding back—often there is combat happening directly in front of us. In a game where one of the mechanics is being “revived” by one of your allies, it is disturbing when one of them runs so far afield. Even without that mechanic, the nature of this game is one of squad tactics. It simply doesn’t make tactical sense to leave your group and go deep into a group of enemies like that.

The issue (both friend and foe) could be solved by a better decision selection algorithm that takes into account proximity better. This could be achieved in two ways — first by scoring individual choices better (e.g. including better opportunity cost for cover points), or on the whole by including influence mapping. Certainly, influence mapping would then be rolled up into the decision-making process, but you could manage better mathematical decisions without necessarily inducing the overhead of an influence map.

There is no concept of “personal space“.

When the characters are supposed to be idle, I’ve had a number of situations occur where my allies were simply not paying attention to me or other allies. They will bump into me in an open area obviously trying to get to a spot on which I’m already standing or at least near to it. There is no concept of “personal space” even to the point of them trying to be in my space.

Sure, much of this could be solved by the inclusion of simple steering and separation algos, but I have to wonder if the decision of where to go isn’t being locked in too early and therefore overriding the sensibility of how to get there. What was a legitimate destination when you started there became a poor choice by the time you were half-way. Therefore, you either look like an idiot going there in the first place or, once you get there, you immediately change your mind and go someplace else. This would certainly lead to some of the “running around” behaviors as well. The solution partially lays in updating your target location often. Sometimes, changing your target location is really not that big of a deal anyway. If your goal is simply a random walk, your destination is unknown to the observer and largely irrelevant anyway.

Working Together

One thing that I haven’t seen (yet?) is a good sense that the enemy is working together. I mentioned this in my First Look post on the game over 2 years ago. Having played plenty of Halo 3 and Halo: Reach, I’m used to seeing the “organized fall-back” behavior that was built into their enemy AI. Not seeing it here in Gears 2 is actually kind of startling by its absence. Certainly building in that kind of behavior goes beyond the AI brain of the characters. It needs to be designed into the levels, etc. That may not have even been an option for the Gears team much less a consideration. I just wanted to point out that I “felt” it not being there.

Anyway, I’m not done with Gears of War 2, so if anything else comes up, you will see it here.

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.

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