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An Alternative to Aggro
by Bart Stewart on 09/02/09 02:18:00 am   Featured Blogs

The following blog post, unless otherwise noted, was written by a member of Gamasutra’s community.
The thoughts and opinions expressed are those of the writer and not Gamasutra or its parent company.

 

I'm on record as opposing the mindless cloning of the "aggro" mechanic into new MMORPGs.

The expense of real-time collision detection was why the aggro hack was invented. Without it, NPCs could simply walk through burly front-line player characters in order to get at the chewy nougat center of the weaker characters behind them. So "aggro" was created as a quick and dirty gameplay mechanic that would allow front-line players to get NPCs to focus on them. It solved a problem by adding active gameplay content -- what could go wrong?

What went wrong was that the concept of the "fighter" was transmogrified into the tank role. Once that decision was made, it seemed perfectly natural to convert mages into damage-dealers and clerics into healers with crowd-control and buff/debuff support abilities.

And then other developers copied this mechanic for their games. They even "improved" on it to the point that aggro management has come to dominate not only character class/ability designs, it's now the default model for the combat play experience. A PvE fight in one of today's MMORPGs is not about smart tactical use of the local gameworld environment; it's about using character skills (like /taunt) that were explicitly created to "manage aggro."

So how does implementing this system in every new MMORPG make sense now that the technical limitations that led to that mechanic no longer exist? I believe it doesn't. With today's technology, proper collision detection and, more importantly, better combat AI can be implemented. The aggro mechanic survives now only through cargo cult game design, copying it because other developers have copies it, then rationalizing that decision by pointing to gamers who -- because they've been offered nothing else -- now believe and assert (loudly) that it's mandatory.

It's not. It's a convention, nothing more.

All that said, opposing something is easy. If I'm against aggro, what am I for? If I favor getting rid of it, what should replace it?

Until now I haven't really taken the time to suggest an alternative, which I think is a necessary element of constructive criticism. So this essay is an attempt to draft such an alternative. I don't think it's a complete solution, and I know it's not perfect. It's just one possible starting point.

AGGRO MANAGEMENT IS NOT COMBAT

"Aggro," for those new to this issue, is a combat AI mechanic used in most online games (MMORPGs in particular) to allow non-player characters (NPCs) to decide which player character to attack.

Aggro (defined as hate on Wikipedia) works basically like this: when an NPC needs to choose which character should be attacked next from a group of player characters, it consults an internal list of "aggression" values. For each player character in the group, the attacking NPC calculates an aggression value based on various qualities of and/or actions by that PC. It then aims its next attack at the PC with the highest aggression value. That player character is then said to have "aggro'ed" the attacking NPC.

The natural outgrowth of this aggro concept is that players will want to be able to do things to "manage" the aggro of attacking NPCs. The "tank" role comes first, because it's obvious that if players can control who gets aggro'ed, they'll want that aggro to stick to the character with the best defenses, leaving weaker characters unharmed and free to do other things like apply damage to the NPC or heal the tank. Group combat, then, gets defined in terms of role-based aggro management -- carefully choosing and timing actions to do as much harm to the enemy or as much help to one's group as possible without shifting aggro away from the tank PC.

My question is: when did people start confusing "managing aggro" with having an interesting tactical combat experience?

What in the world does "managing aggro" have to do with letting a group of players make intelligent and cooperative use of a rich set of environmental phenomena to achieve tactical superiority? How does the artificial and arbitrary gameplay of "aggro management" make any use whatsoever of the IP, the setting, on which a MMORPG is based? How is "performing actions intended to control the internal aggro calculation of an NPC" anything like "combat?"

If people think they like the aggro game, that's fine. People are free to like what they like. But the fact that some people like one particular solution to a game design question does not imply that it's the only possible solution. As gamers, we should be expecting game developers to look for more enjoyable solutions to game design questions, to try to create new and better solutions, not to merely clone mechanics that might work for some other gameworld. Importing the "aggro" mechanic from ground-based fantasy combat games into new games -- including even science fiction games -- presents the appearance of laziness.

So instead of aggro, I'd like to propose an alternative approach to NPC combat decision-making, which for lack of a better name I'm calling "cultural tactics."

CULTURAL TACTICS

Cultural tactics assumes the existence of a story. When there's a background story providing opportunities for narrative development, that story can and should be used to inform the behaviors of intelligent NPCs.

This is done by assigning cultural qualities to every non-player aggressor (NPA), such a non-player character or a tank or a spaceship. All individual NPAs will be defined as belonging to a primary culture. While some individual variation may be possible, those cultural qualities will tend to determine the choices that an individual NPA makes in any situation. Those choices may be about combat actions, or they may be about diplomatic actions or anything else the NPA is able to do. All possible forms of interaction with player characters would be produced by a goal-generating system whose rules would take as inputs the cultural attributes of the decision-making NPA, unique (probably randomized) attributes of the NPA, relevant aspects of the local environment (including perceptions of player character resources), and a desired goal state.

What's important to see here is what's not listed as an input to this decision-making system: player character actions. Getting good combat behavior out of an NPA actor does not require allowing players to directly manipulate that decision-making process. It might benefit from it in extended interactions, such as strategic-level conflict, but the typical short tactical fight does not require NPAs to use player actions as decision-making inputs.

As for offering that capability because it provides gameplay (e.g., aggro management), that's true, it does... but when that gameplay takes over, completely shifting the attention of players from interacting with elements of the gameworld to the manipulation of arbitrary rules that have nothing whatsoever to do with combat, then if that mechanic isn't required, it does not need to be implemented.

Cultural tactics would allow NPAs to have an appropriate and interesting degree of autonomy. Instead of being the pawns of players in gameplay that distracts from the gameworld, NPAs whose actions are based on attributes of the story-based culture to which they belong would choose combat targets in a way that tells us something interesting about who they are.

In a space game, for example, an NPA from a mindlessly aggressive culture might simply target the nearest ship. (Maneuvering into and out of an NPA enemy's range would thus be a viable combat tactic for groups of player characters up against ships commanded by members of such cultures.) An NPA honor culture might always try to target and destroy the strongest (however that's defined) player ship; a ship commanded by an NPA from a victory-at-any-cost culture might seek to destroy the weakest ships first.

A nasty pirate might go after the ship that appears to have the most/best weapons. A daring privateer could be culturally inclined to attack the ship that might carry the most interesting advanced technology. Members of a cybernetically enhanced culture that shares a hive-mind (you know who you are!) might simply attack randomly -- they're big enough not to care what the typical opponent looks like -- or they might look for whichever ship acted like the leader in order to disable the target group's command hierarchy.

LIFE AFTER AGGRO

The point behind all these examples is to show that aggro is irrelevant. Aggro is not necessary for non-player aggressors to be able to make interesting choices about whom to target. And getting rid of aggro serves the useful function of eliminating the bizarre focus of players on withholding their gameplay actions in order to avoid being noticed by a vastly stronger NPA foe, who then hammers their characters into pulp most instantly.

Without being forced to play the Aggro Management Game, players are free to engage in actual combat-relevant tactical decision-making: should I try to maneuver to my target's rear facing, or would it be better to try an alpha strike now? Can I use the particles in the nearby nebula in some interesting way? Is there something cool I can do with one of my weapons right now instead of having to hold my fire because it might make an NPA mad at me?

In summary, if the aggro mechanic works for other games, fine, but it is not required for every game. It can be discarded with no loss, and with considerable gain, since not having to withhold one's combat actions for fear of attracting damage-dealing attention allows more players to participate more frequently in the fun.

It also means they don't have to have all of their actions squeezed into the subset considered appropriate by some developer for a particular and narrowly-defined combat role like "tank" or "crowd control." That permits players much more freedom to play the combat game in the way that's most enjoyable to them.

Roles are still possible; the beauty of getting rid of aggro is that those roles can then be defined in ways that make more sense for the setting of a particular MMORPG. And even without aggro, NPAs are fully capable of selecting their targets in fun and meaningful ways.

If all that is accepted, then yes, I find it disappointing that MMORPG designers continue to clone the aggro mechanic for their games. If they really believe it's necessary, that's a shame. If they don't, it's a wasted opportunity to do something better. Either way, the concept of "aggro" is long overdue for retirement.

CONCLUSION

I'm under no illusion at this point that the producers/designers of any MMORPG under development will read this and think, "Say, you know, he has a point -- right, everybody stop what you're doing; we're going to re-do combat even if it means shipping four months later than planned!" I assume that the aggro mechanic and its tank/DPS/support handmaidens will be the default choice for the core combat model of every new MMORPG for years to come.

The point of proposing and explaining this alternative is therefore not to try to change the minds of big-studio game designers who clone MMORPG conventions as a risk-reduction technique, but to suggest to the newcomers that there's room for innovation here. By all means, look closely at the aggro management model of combat, analyze it, consider its first-order features and second-order effects within the context of your other game design choices, and use it if it makes sense for you... but also feel free to go with something else if aggro management doesn't feel right for your game.

Big-budget games that try to play it safe don't always succeed. So why not take a few carefully-considered risks and try something different, such as deep-sixing aggro in favor of a combat model that's actually related to combat? It's not like your odds of success will be much worse than those of the play-it-safe developer. :)

In fact, given the wealth of conventional MMORPGs available currently, this might be exactly the right time to break away from the pack in a few key areas of design.

Why not start with aggro?


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Comments


Timothy Ryan
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Aggro has its roots in non-MMORPG games. Ever played Double Dragon? Aggro is almost as old as the health meter. Aggro is based on a very human-like response to threat, which makes it easier to predict how the AI is going to react to player actions.



Every game with AI that has choices on whom to attack has had its own system for choosing targets. In the case of MMO's, there is a very real concern about lag which makes knowing the exact position and facing of combatants imprecise. That makes "real combat" reactions based on arc etc. very muddy. The amount of damage and the use of specific abilities to grab aggro is much more controllable and predictable for players.



The games still use combat arc to factor in damage - either by reducing or eliminating dodge and blocks from attacks that come from the rear, or by awarding extra damage (backstabbing) to attacks from the rear, or similarly making certain moves only function in certain arcs.



If you REALLY want to tackle something worthy of a make-over, it's not the aggro mechanic. Tackle the spawning and wandering AI, who seem as unrealistically convenient to kill as crops are to farming. MMORPG's need to look back at the AD&D playbook to see how monster encounters should be staged. Remember when the DM would say, "Your elven ears are picking up some movement in the brush, or your half-orc eyes see the infra-red outline of a grotesque shape closing in on you. Roll the dice for initiative to determine if you're surprised." There's no surprise in MMORPG when the creatures just spawn and wander about for seeming no reason other than to pose a threat on the horizon.

lee cummings
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I'm not sure about this - aggro mechanics are present in games for very solid reasons.



Yeah, its interesting to suggest that in an encounter a specific type of enemy relentlessly attacks the weakest member of a group (say a healer in an RPG), but how much fun is that if you're the healer? Or the tank, who's adding nothing to the fight outside of lousy damage output? What does that enemy AI add to that encounter in terms of game play? The healers are spam healing a weaker character more, as opposed to just healing the "tank".



Having aggro modification abilities are there not only to make gameplay somewhat predictable, but in more complex encounters it adds more complexity and challenge, and puts necessary limitations on some classes. Offensive casters can't just nuke happily until the cows come home, tanks need to act in very specific ways at specific points during encounters to hold / regain aggro, etc)



What you propose seems to be simply adding storyline reasons for certain enemy behaviors to exist, however these behaviors are already out there. Almost every single example can be seen in an MMO on the market today, they just don't have storylines to back them up (Cazic Thule being completely insane and deathtouching people randomly, the Hateful Strike mechanic in WoW, etc)



Adding stronger in-story reasons for these enemies behaving the way they do would certainly add to the depth of the encounter, however these behaviors as game mechanics will still work the same way for 99% of players, especially in battles of smaller importance - they engage, work out what the enemy is doing, and respond. On top of depth the only advantage storyline would have is being able to put the player in a slightly stronger position at the start of that battle.



Aggro in many games is simply a way to display an enemy's AI state numerically, so it can be altered by numerous factors. In your examples "aggro" still exists, it's simply more fixed and less flexible.

Kim Pittman
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Discussion is always a good thing.



I still see aggro numbers in the examples you have given. They are just more specific and have logic behind them as opposed to understood numbers. I think that the use of things that change the aggro mechanic for a fight is interesting and changes the strategy enough to make it interesting. More ways of doing this, such as your examples, are needed and would make games more interesting from a strategic standpoint.



I would argue against removing aggro entirely because this would require classes and players to all be able to survive a few hits from a boss. That means more health, more armor for all, and suddenly you have lost the delicate balance of dps/tank. Class homogenization takes a valuable facet away from the game and the strategy that is needed in these games to make them more than just a grind. This is especially apparent if you have ever run an instance in WoW with 5 Death Knights. It quickly goes from strategy (sheep/silence the healer, this kill order, etc) to hack and slash, keep moving.



Even pen and paper games have a form of aggro mechanic to prevent the glass cannons from being smashed.

Andre Gagne
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@ lee



It is my understanding that without an aggro-mechanic the role of "tank" or "healer" would be less set in stone.

With a different type of AI the combat itself would fundamentally change and be, potentially, more interesting.



Your comment on how aggro limits some classes is interesting, as that would mean that something new would have to go through lots of prototyping to make sure you don't get an uber class. perhaps a change to spawning mechanics (and hiding mechanics) would help. Hidden mobs would be interesting.

Joshua McDonald
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Improving the aggro/group roles system has been on my mind for some time, now. I like this post, partly for the suggestions it offers and partly because you're challenging something that needs it.



One thing that you brought up but I think you could have spent more time on is the collision thing. A tank, for example, instead of (or at least as a complement to) taunting abilities could have a large footprint, and a powerful "free hit" ability on any unit trying to disengage from him, whether it succeeded or failed (AI, of course, would have to have some intelligence in choosing when to try doing this). That would stop the tank's job from being mindless like it is now and also put limitations on the tank where he simply can't be expected to hold every enemy. Fragile characters would often have to rely on the tank, while tougher ones would usually need to fend a bit more for themselves or sometimes even help him in his role.



This would also loosen up the group roles a bit from their current state. Hybrid characters would actually become important again. A tank's damage dealing might become important enough to trade off a little durability, new roles may arise, etc.



Before people criticize this, keep in mind that you couldn't just drop this sytem into an existing MMO unchanged. Numbers would have to be substantially different than they are in the current crop, and the pacing of fights would need adjusted (what does Kel'thuzud care if the tank gets a few free hits against his millions of hit points when he attempts to bypass him).



Also, this is not the complete system, just a small portion. I like Bart's cultural tactics, which would go very well with what I described, and I still support some player manipulation of aggro (but in a tactical way, instead of a mindless repetitive way, as you see in the current scene).

Aaron Casillas
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"A PvE fight in one of today's MMORPGs is not about smart tactical use of the local gameworld environment;"



This is the key thing to keep in mind, the order of combat should be dictated by the shape, language and geography of the world; concealment, cover, height and natural borders. Otherwise its like shipping a game of chess without the chessboard. Although aggro pull and push systems keep the notion of distance, they normally lack the notion of bio-geographical strategic/tactical nuances and topographical advantages.

Maxime Doucet
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I totally agree with the original blog post in that aggro has been used throughly in MMOs for the past 15 years and it's time for a change. The solutions brought forward are interesting, and I think part of the answer lie in the behavior of the players themselves in a PvP environment.



For instance, we've all seen PvP combat enough to realize that tanks usually represent the lesser threats; mages, archers and healers are usually the primary targets while the tanks get busy at hindering their enemies' progress with move debuffs and stuns. So if a group of NPCs mindlessly aimed for the group's "soft core" of robe-wearing casters and healers, it would make the gamers' experience unpleasant and even more predictable. (The AI should at least be able to compare both possibilities: should I attempt to take down the tank who's standing in front of me, or should I try bypassing him and aim for the healer, who's 20 yards behind him?)



A good solution, then, would be some kind of "cued predictability" system whereas mobs will somehow announce their next targets, using an audio and/or visual cue. For instance, a race of undead might have a natural hatred towards all holy magics; they will therefore charge into battle yelling "Death to all clerics!", giving the PC group a chance to organize accordingly, using terrain, paths and collision formation and brace for impact.



This can be done at the beginning of a fight or during a fight, as mobs could switch target at random or following certain events.



In certain games, PvP encounters happen in which the class and powers of the players were kept hidden, making it hard for our opponents to properly prioritize targets (i.e. Thanes and Healers in Dark Age of Camelot). But then, as soon as the Healer casts a healing spell, he becomes target #1. This kind of behavior could also be used with AI. A player could be perfectly safe in a fight until he performs a certain action. Casting a fireball could anger a water elemental, raising the dead could do the same with a druid or cleric.



This would make the whole PvE encounters much less predictable and more adventurous, and way interesting for an experienced player as well, as the players would encounter mixed groups of different kinds of mobs with widely different AI behaviors and triggers.

Lance Rund
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Asheron's Call (1999) had (has, actually, it's still up) collision and the concept of "holding the line" as a major gameplay mechanic. The side effects that weren't so desirable were that variable network latency could destroy otherwise excellent combat mechanics, and that griefer players could block choke points or disrupt formations. We now live in a low-latency broadband age, though, and the playing field is significantly more level.



If a mob can only attack one person at a time, the AI has to have some basis for sorting available targets. No matter what you call it... it's aggro. The problems associated with aggro, as described in the article, are really twofold:



1. It's called out specifically in player combat moves (can we make the man behind the curtain a little more obvious, please?) and there is therefore a direct link right to the aggro numbers. Some games even have built-in "threat meters", not from players making estimations on how the mechanics work, but straight from the game server itself.



2. Aggro is easy to reverse-engineer on games that don't directly publish it. A few hours of experiments, some curve-fitting and spreadsheet work, and there you have it. Maneuver X gives Y points of aggro, maneuver Z gives Q. Event A causes the aggro table to reset. Aggro mechanics are too simple.



Aggro management as the basis for combat in multiplayer games exists for a reason, though. It provides players with an axis of skill. "If we do X and Y and Z, we can manage the damage incoming, and therefore win." Players like to win because of their skill (or at least believe that it was their skill!). It also prevents frustration. If the players get it into their head that there is too much of a random factor in who the bad guy attacks, they're going to be quite upset.



So yeah, it's a tightrope to walk. The fact that aggro is now part of the axioms of MMOs doesn't make it any easier... people like newness less than they say they do. Whoever comes up with a more interesting system that doesn't alienate players with expectations set by previous games is going to be rich.

Johannes Smidelov
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An interesting aspect in this comment thread so far has been that some defend the aggro-mechanic as it would disturb the balance of tank/dps/healer if it wasn't there, which is a bit like defending mouse-look in a FPS because it would be difficult to fire the Rocket Launcer without it. And, indeed, it would be difficult, but the Rocket Launcher in this case is the result of mouse-look, not the other way around (bad example, but it makes the point clear).



And although discarding the aggro-system as a whole may not be necessary, it does need some twists. Like Maxime suggests, some classes may be more frustrated by certain abilities (or even classes!) then others or, like Bart suggests in the original post, certain cultures may behave differently. Or perhaps someone standing in line-of-sight gets a percentage higher aggro then someone who doesn't, which changed as you move in and out of it... there's a lot of modifyers you could experiment with, and making the aggro less uniform would likely make fights interesting in a "how do we fight this?"-way instead of "what's its abilities and how do we counter it?"-way.

Thomas Whitfield
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I won't say it is easy to get rid of, but this idea is another nail in the coffin of class /role systems as they stand.



WE can do without tank/dps/healer model.



If we even out the HP and DPS, it won't matter which PC the baddies hit. Class becomes a style choice rather than a role choice.



Warriors mitigate damage with armor, do damage with weapons, mages mitigate with dodges and shielding, damage w/ spells, etc.etc. If everyone does similar damage, and can take/not take a beating with equal efficiency, then combat based on geography and AI can take place much more easily.



Everything you can do becomes style rather than a pigeonhole.

Christopher Wragg
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Well I think the dropping of "aggro" an imprecise concept. Technically any kind of targeting rationale is an aggro management scheme, just of varying complexity. You have to determine how your foe chooses it's target somehow and aggro isn't a bad rationale. What ought to be changed is how each opponent generates aggro. I'd create a bunch of personality types, which assign a set of simple aggro rules and reactions, and a simple set of methods for combining personalities, so Coward(2):MageHater(1), basically rationalising that aggro is generated mostly from the coward side of things, and in any situation the AI has to choose between actions, it picks the coward action. Then maintain a list of Ability Aggro values. These things determine where special skills get used, and they reset after use, so many skills might simply use a generic aggro value, but an AoE skill might generate aggro for allies that stay close to one another, like for instance all the melee around the boss. It then simply uses generic aggro to make a choice when all else is equal.



So for instance a goblin mage (Coward(2):Caster(1) personality) might run away from the enemy with the highest aggro, enemies generate aggro faster than their peers for merely being close, but when nothing is close the thing that hits hardest is the focus. The mage has a silence skill and a blind skill, he'll use them on the most threatening mage and ranged character, while maintaining distance from everyone, he'll use his aoe attack when several people are closest together. Otherwise he throws little fireballs at the weakest target. It's easy, it's simple and it's aggro, it leads to interesting engaging combat, and if you want to make use of another factors (terrain and sight values) there's always room to add them.

Enrique Dryere
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I'm all for rethinking the mechanisms of aggro, as it is a vital step in breaking the tank, healer, DPS mold, which is a must.



I believe the way to actually do this is present in the boss battles of single player games, which can generally be beaten without taking damage, if the player is skilled and elusive enough. Somewhere along the way, MMORPG devs forgot this was a possibility for bosses. If there is no need for constant damage output, that means every attack could possibly be avoided by any class in some way.

Matt Kane
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Aggro is simplistic and limiting.



Unfortunately many of the solutions you present, even if implemented in the "cultural" cornucopia you propose are even more simplistic.



You would have to assume the variety of AIs would lose most of its effectiveness to enhance the challenge and depth of gameplay after only a short period of time since players would quickly learn the ins and outs of identifying AI archetypes in enemy NPCs. So now you are in a situation where instead of managing the few simple nuances of 3rd generation aggro mechanics, the player is managing perhaps even simpler mechanics that may be more predictable. Removing threat capping for dps won't necessarily open the door wide open for more engaging gameplay either, although it may diminish the role of healing.





The real culprit here is the design of typical raid encounters. 1 big raid boss sitting still for 5 years picking his nose waiting for a group of 4-50 random guys to come and hack at his shins for 10 minutes and 24 seconds til he suddenly dies of congestive heart failure.



The boss has no goals. If you wouldn't have come along with your group of buddies, he would have probably continued to pick his nose for another 5 years.



So designers compensate for the fact that they develop enemies and encounters with no purpose by imposing standardized, shallow enemy motivation.



Instead of attempting to conquer the world, your terrifying end boss to the dungeon you've been trudging through for hours is actually playing whack-a-mole with one of your UI elements.



A good start to solving boss mechanics would be endowing bosses with motivation and purpose (beyond dialogue text).

Harold Myles
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Even though I agree with some of what you say in this post. I think a few of your premises are a bit off.



First, there is nothing preventing the 'solutions' that you present from being incorporated along side an aggro system. As well, your proposed 'solutions' don't actually provide most of the things aggro tends to provide: role definition, and a clear set of rules that the players can know in advance (which is usually good for most games), in addition to some technical features like minimal load on AI processing, among others you mentioned.



Secondly, without getting too deep into semantics about genre's and mechanics etc.., aggro can be viewed as a game in itself. A game people obviously enjoy playing. Saying lets stop making aggro games is like saying lets stop making block-stacking games, tower defense games, or bridge construction games.



As long as there is some innovation then there is nothing wrong with reusing and expanding what came before.



No one is forced to incorporate aggro or base a game off the mechanic. But proposing it be thrown away, considered irrelevant, or discounted because you would prefer a different game is a bit off. Go play a different game, or go make a different game, but don't be too disappointed when people keep playing with aggro.



On a side note. There already exists a solution for the portion of audience in an mMo (emphasis on multi-player) most interested in 'Combat'. Its called PvP.

Jamie Mann
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So... there's a problem because players have figured out the targetting criteria being used by NPCs? I'm not sure there's any real solution to this. barring the evolution of significantly more powerful AI.



(Also: I have to admit, I'm not a MMORPG fan, but I'd assumed that NPC aggro was tailored on a per-class basis - is this not the case?)



The best solution would be to design co-operative NPC behaviour - for instance, long-range snipers could choose whether to target the tank attacking their boss or the healers backing up the tank...



However, a better question would be: is this a solution looking for a problem? What we're basically talking about is making the gameplay more complex, which in turn means that players will have to expend significantly more effort in overcoming the obstacles.



This may not be a bad thing - and I know a lot of people who enjoy coordinating complex battle scenarios. However, I also know a lot of people who wouldn't enjoy it.



Finally, as Harold has already pointed out, there's a solution for people who do want complex, non-deterministic gameplay. PvP...

Andrea Di Stefano
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In my opinion, aggro systems aren't flawed "per se", it's their usage that poses a problem. In a way, aggro is a fairly realistic mechanic: imagine finding yourself in a street brawl, chances are that you will be managing your opponent's aggro as a part of the fight dynamic!



As games tend to replicate fights with "realistic" dynamics, I think the aggro mechanic is bound to stay. But its inner workings are bound to evolve greatly, with environmental (cover possibilities, etc.) parameters playing a greater role.



More importantly, as long as the players are able to crack the aggro system and learn to manipulate it, aggro management will survive as a play style.



Maybe a more "organic" approach would be effective? A system defined by a series of player/opponent parameters, themselves influenced by other environmental parameters...in the end, the aggro system would depend on enough variables to prevent it from being predictable...

Owain abArawn
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Agro isn't the problem as much as class implementation and simplistic AI are related problems. In the example given of the tank, yes lack of collision detection does give rise to artificial mechanisms like Taunt, but the fact remains that the mob probably really does want to go after the mage or the healer first because from a dps point of view, the warrior isn't the biggest threat (which is a design flaw in itself, to my mind). Without collision detection, to justify the existance of the warrior at all, you need artificial agro generators, such as Taunt, or Challenge, or whatever you want to call it.



Where it really gets absurd is when you are fighting multiple mobs. The smart group will have the nukers hang back until the tank effectively gets all the mobs under his wing. So the tank attacks/taunts/AOE taunts all mobs in the group, ensuring everyone is securely locked on him, and then the call goes out. "LET THE FACE MELTING COMMENCE," and it's pyrotechnic time. Every tank class guide I've read from multiple games have variations on this theme, and even if there were collision detection, one tank shouldn't be able to engage multiple mobs. At best, he could handle one or two, and the remainder, IF THEY HAD AN EFFECTIVE AI THAT WAS WORTH A DAMN, would bypass him in order to get to guys shooting sheets of flame at them.



So, as I have maintained elsewhere in these forums, classes by themselves are not the sole problem, nor is the lack of an effective combat model (no collision detection), nor is poor AI, but rather it is the combination of all these defects that I object to. If you had effective collision detection, and intelligent AI, then when people start looking for a group (LFG), the standard 1 tank, maybe an off tank, a healer, and a bunch of nukers will no longer cut it if you expect to enounter large numbers of mobs. If you want to protect the squishies, you will now need a formation of warriors and a shield wall, which would certainly be far more realistic.



"To the everlasting glory of the Infantry..."

Harold Myles
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Sorry I have to comment again. The original post and many of the comments are under the impression that somehow players having direct or semi direct control of AI is a bad thing, or wrong, or some sin of game design. Player control over AI (an aspect of Aggro) has deep roots in gaming and is a perfectly valid mechanic. Some examples:



1. Lode Runner: From the original (1983) to the newer release on XBox Live, a principle aspect of this game is that the player can completely determine how AI reacts to stimuli and can/must manipulate them. The majority of the puzzle levels for this game employ this mechanic.



2. Donkey Kong: For those players in the Deep gameplay, knowing how to manipulate the various enemies is what keeps good players alive. The designers might not have planned it that way, but this mechanic is what gives Donkey Kong its staying power. Without it the game would probably be virtually unbeatable.



3. Geometry Wars 2: Pacifism Mode. Unbelievably deep for how simple it is. This is the pinnacle of game design IMO. A circle and some diamonds. You can move and the diamonds chase you. How simple is that and people play for hours, days, weeks, months. The AI is completely deterministic and you have control over it; you move and they come to you. The key is getting them to do what you want.



As I mentioned before, if you don't like Aggro that means you personally don't like that particular game or game style. And your personal taste don't invalidate it as a game or as good mechanic. You might be bored or tired of it, but it is still relevant and waiting to be expanded on, merged with other game styles, or simply used just like all the other stuff in the toolbox.

Maxime Doucet
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I don't agree with the last couple points. Provided most of the comments are from players who have played MMOs extensively, it's become easy to imagine better systems, namely for random battle events and spawning mechanisms.



I do agree that Aggro as a threat-assessing system for AI should still be used in certain situations - when caster A and caster B are positioned the same way on a battle field, caster A should be a primary target if he inflicts more damage - but it should not be the main mechanism onto which all other sub-mechanisms depend.



There should be a whole series of triggers to adress specific situations, such as the originally proposed "cultural tactics" or the way PCs and NPCs are situated in a battle. How is it that, in 2009, players are still stacking mobs onto a single spot to AoE melt their collective faces? There should at least be a simple trigger to avoid such situations.



LoS is also now common ground in MMOs, so why can't the AI use obstacles and other terrain features and formulate simple group strategies, much the same way they do in first-person shooters and strategy games? As it was pointed out before, we're now on very high broadband Internet, with relatively low in-game latencies.



Also, random events should be generated throughout encounters. In World of Warcraft, mobs will usually start running when they're at 10% health; but why can't they start running earlier if they see there's no way the fight can be won? A diminishing return mechanism as a penalty for engaging battle against weaker foes. A mob should have a list of possible moves he can perform in a battle - instead of just using a Disarm, he should have Bleed style, Sprinting Escape and Armor Debuff styles available as well, which would be performed at random throughout the fight.



Perhaps the only reason MMOs are still using old mechanics is simply to attract the same old crowd?

Timothy Ryan
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The most fascinating discussion has erupted over this simple topic. While I didn't agree with the author at first, I can now see how strongly opinionated the hard-core MMORPG players are particularly in regard to traditional player class roles. I concede that aggro (acquiring it/maintaining it/manipulating it) has probably become much more complex and taken a far greater part of combat than is necessary. Do we really want the game to be about the best way to pick a fight with a boss monster instead of what combination of spells/powers and combined tactics a group uses?

Luke Bergeron
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I'm not defending traditional aggro mechanics or decrying them, but there is something to be said for the traditional group roles.



For a long time I played an MMO as a ranged damaged dealer. It was a easy job, I sat in the back and fired my bow, joked with my raid members, killed bosses and went home. After doing that for 3.5 years, I switched roles from ranged DPS to a tank. It was a huge change, because now the focus of the entire raid was ON ME. I used to hang out in the back, now I'm up front. That change, which I hadn't counted on, made the game completely different for me.



The strange thing about the traditional class roles, and why they remain so effective with players, is that some people want to play integral roles and some people don't. The player that chooses to play a tank or a healer does so because they want that extra responsibility (or they move on to a different class), and the player that chooses a DPS class does so because they don't want to be in the limelight.



Changing aggro mechanics to make new and interesting games is great: I'm all for that. Innovation needs to happen or we're just making the same game over and over with better graphics. However, a system needs to cater to what players want, and some players never want to get aggro because they don't want the focus of the raid on them. They LIKE sitting in the back, shooting some fireballs, and going home. That's the way they want to play and the successful game needs to support that.



So, any reworking of the aggro system has to still give players an option to not get aggro (or very rarely), yet still maintain a functional group role.

Owain abArawn
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Upon my first reading, I was skeptical about the cultural approach to agro, but upon reflection, perhaps it's not that far from the mark, but with respect to mobs, again, I think the emphasis should be on AI, and not a simplistic mechanism such as agro. In that regard, I agree, agro, as a game mechanism is severely lacking.



Cultural variation in tactics/AI is realistic. For example, in western nations, particularly democracies like the US, the culture is risk averse. So, where as in WWII, US Marines suffered nearly 26,000 casualties in 36 days of combat on Iwo Jima, but that was considered acceptable, where as from Mar 2003 to Sep 2009, total US casualties in Iraq numbered only a little more than 30,000. http://www.globalsecurity.org/military/ops/iraq_casualties.htm



That's a significant cultural shift, and as a result, western military doctrine uses massive firepower and advanced technology as a means of limiting the number of casualties. Contrast that with Japanese banzai charges in WWII, or the Iranian practice during the Iran/Iraq war of clearing mine fields by marching children locked arm in arm through the mine fields with the promise of guaranteed entrance into Heaven as a martyr. Cultural differences, indeed. http://www.ahwaz.org.uk/war.pdf



So, I could see in a traditional fantasy based MMO, orcs might employ berserker tactics, hurling themselves at the closest enemy available, where as elves might use hit and run guerrilla tactics, and dwarves would employ an infantry phalanx, and humans might prefer combined infantry/cavalry methods, but even within these boundaries, there should be a degree of semi random variation from one encounter to another so that nothing is entirely predictable. In that way player groups can't just use static tactics. You want to be a warrior? You adapt. You overcome. You improvise.



What is best?

"To crush your enemies, see them driven before you, and to hear the lamentation of the women!"

Owain abArawn
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Luke said, "So, any reworking of the aggro system has to still give players an option to not get aggro (or very rarely), yet still maintain a functional group role."



Very true. I dislike class based games, yet I still play MMOs as a warrior almost exclusively. I like the role of the warrior, but I dislike how it is implemented in most class/level games. The question is, how should games handle AI with respect to mobs in combat?



The mob should be interested in it's own survival, so threat has to be a consideration, but it can't be the only consideration. As an archer, yes you may be raining death down on the mobs, and they might dearly love an opportunity to kill you, but they should still have to take the warrior into account, blocking the way, screaming, "YOU SHALL NOT PASS!!!"



The question is, from a game design point of view, how should that be accomplished? In current MMOs, there is an artificial taunt skill that generates false agro because typically the warrior is too weak offensively to generate significant threat otherwise (whose brilliant idea was THAT, anyway?), and no way to physically block the mob either.



So, how much more satisfying is it, from a game play point of view, to preserve the idea of character roles in an MMO, but make it so the warrior protects the archer by skill, strenth of arms, physical denial of access, and the threat of certain death, and not by such puny artificial means as a Taunt skill to make up for piss poor game design.

Bart Stewart
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Thanks for the very thoughtful comments, pro and con. Some quick responses to a few of the key points:



@Andre: Yes, replacing the "aggro management" mechanic with some other target selection mechanic means the now-conventional tank/DPS/support roles have considerably less value. But that does not mean a game can't still provide clear role (and classes or skills that define those roles). For example, a game could offer Heavy Gunner, Light/Mobile Gunner, and Indirect Fire roles. Or how about Tactical, Sciences, and Engineering -- who said that all roles must be combat-specific?



@Lance: Predictability and unpredictability are both desirable in NPAs -- that's part of what makes designing these kinds of games so much fun. :) I would say that something like "cultural tactics" might offer a workable balance between those two competing goods: it provides recognizable patterns of behavior at a high level (cunning, sneaky, direct, brute-force, cowardly, etc.) while still permitting interesting variation in behavior based on the NPA's recognition and use of local environmental phenomena.



@Harold: I should probably have said more clearly that I'm not calling for the utter and permanent elimination of the aggro management mechanic in all games. What I'm trying to encourage is some movement toward providing alternative systems for tactical combat gameplay... and then let's see what players really prefer.



Ultimately, I agree that aggro management is a valid play mechanic for representing tactical combat. That does not, however, imply that it's the *best* (or should be the only) mechanic available to MMOG players.

Thomas Langston
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I think that collision detection is an unessential addition to many games. Instead by merely giving defensive characters the ability to slow, stop, and push nearby opponents the feel of a defensive line can be achieved without watching players bounce around each other.



If your goal is to remove taunts, the defensive characters could have more abilities to slow, intercept, or interrupt attacks, increase nearby players defenses, or by greatly increasing the defensive character's offensive abilities if they aren't attacked. Ranged attacks in particular should be difficult with a defensive character in melee range for a taunt-less system to work. In general the effect is the same, the enemies attacks are less effective useless unless they are directed at the defensive character.

Dave Mark
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I will be giving a lecture next week at GDC Austin on how better AI in MMOs can encourage better community gameplay. Rather than respond to 20 different people here and on other similar posts on this subject, I posted a mass response to my own Expert Blog.



AI and MMOs - The Controversy

http://www.gamasutra.com/blogs/DaveMark/20090906/2942/AI_and_MMOs
__The_Controver

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Christopher Wragg
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I've always liked emergent state based AI personally. It's easy enough to declare a combination of states and then a resolution hierarchy. For instance set up 4 really simple states, attack, defend, retreat, under attack, then simply write a set of rules for each enemy class type (healer, mage, warrior, rogue), that define the generic behaviour of a class in that state. Add a simple aggro rationale for each class type that determines state changes, then give abilities a descriptor, self defense, ally defense, ranged attack, melee attack, attack skill, heal, aoe, aoe heal. The rules use these ability descriptors to describe the rules. For instance an attack rule for a warrior type might read; "if meleeAttackSkill = available". Then for each enemy in your game all you need to do is write stats, class type, and skills, then during combat they each get resolved by the state engine. Now if you want really morphable entities you could even write a rationale for group combat that upon loosing class type, another character attempts to act like it (effectively switching state engine).



Ultimately really simple tactics like this don't take too much thinking about, and actually lead to some really emergent enemy tactics, especially if you give skills that do things like reduce or increase the aggro generated by a player to mobs. Like a warrior attack skill that damages armor might have a (hidden from the players) modifier of rogueAggro = 2, so that character now generates double aggro to rogue types (because they're more vulnerable to attack). In a group of warriors you might have all the other warriors try to separate their wounded comrade from the enemy simply by each warrior type trying to get between their wounded ally and enemies during their defence state.



True state based engines of course can get quite expensive (to run) across hundreds of units, but if you're dealing with only 10-20 enemies with simplistic states it shouldn't be hard to do something along these lines, could be wrong though....

Adam Logghe
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The AI in say World of Warcraft is really not noticeably improved from the AI I fought in Ultima 1 in 1981ish.



Distance based aggro that leads to an attack rotation.... seriously? 2009?



AI really does needs radical improvement in MMOs.



I'd like to see a system in which there was some morale and motivation system in the mobs.



If the mob sees you in your shiny epics he decides you are too much of a threat and gets allies perhaps?



If you are even more obviously too tough the mobs should flee from you as you ride through their camp.



I agree that traditional dumb aggro should die though, as you point out its mostly a cheap mechanism that is outmoded regardless of its "ease" for game designers.



People shield blocking physically the mob from its intended target "frustrating" it and causing it to perhaps focus more on pushing or circling around versus doing direct damage might be a great strategy and play mode.

Bart Stewart
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Well said, Adam. It would be interesting to see the environment (terrain, ambient weather effects, etc.) play a larger role in tactical gameplay.



Basically I find it bizarre that people not only seem satisfied with the artificial minigame of "aggro management" rather than tactical combat, but some will actually defend aggro management merely because they've never known anything else.



Still, I'm hopeful that some developer someday will prove that games can succeed even if they don't let players magically dictate whom NPCs will attack....


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