Walk and Think like a Skeleton – Part II

Posted on by in Development, AI

You already know what kind of problems with the enemy AI we encountered in the early stages of development. Now it’s time to go into details about how we’ve improved and expanded the AI of one of Hellraid’s many enemy types: the Skeleton hordes.

The first step was to create probable battle situations. If the player is surrounded by groups of Skeletons, one of possible scenarios is that the strongest units attack first. Or, another strategy, a number of weaker units engage the player in combat, while the rest block the escape route or hunt the remaining cooperative players.


The Skeletons have to be able to evaluate which strategy will be the most effective against the player(s). They need to consider such factor as the terrain configuration, their headcount, and the player’s equipment and skill level. Then the AI decides if it’s best to make a massive frontal attack, lay an ambush, or perhaps wear the player down in a series of duels and smaller skirmishes (1vs1, 1vs2, 1vs3).

The expanded AI created a need for new animations. Consequently, we added evasions and dodges, counter and parrying animations, sneaking and encircling, and finally taunting, which is characteristic for units not directly involved in the fight at the moment. It also makes the gameplay more varied and dynamic.

Right now, out testers are hard at work trying to “break” the game and find holes in the new AI of the Skeletons. The testers set up traps, attack the poor Skeletons from all sides simultaneously, or drop heavy objects on their heads. This way, we create new situations to which the Skeletons should be able to adapt with the help of our HTN Planner.

One of the most basic problems was how to stop the Skeletons from getting in each other’s way. One unit evading the player’s attack would often bump into another unit, who happened to try to join the fight. We’ve solved this problem by introducing a new condition that cancels an evasion if there’s another AI character in the way. While we were at that, we also fixed path finding as to prevent the Skeletons from approaching the player from behind the backs of their AI comrades.

Another problem, which we’re dealing with now, is detection of dynamic objects on the map (such as corpses or destroyed objects) that may block the AI’s paths. We’re also in the middle of eliminating “synchronized dances”, as we call it.

A synchronized dance is a case when many enemies choose the same attack pattern at the same time, which looks like a group of clowns mocking each other. To avoid this, we improve not only the group AI coordination, but also create new variants of attacks and reactions, expanding the range of available behaviors.

We’ve still got much work ahead. We haven’t finished refining the elements we added to the AI yet but we’re already planning to introduce new conditions and behavior patterns that will make the combat in Hellraid a truly unforgettable experience.

To give this blog update a nice closure, we have a question to you: what kinds of behavior, beyond what we mentioned above, do you expect from the AI-controlled Skeletons?

Comments (34)

This is actually my first time ever writing something on a forum. I just want to say I am soooo excited for this game. Extremely impressed with how you have taken the ideas and opinions of your future gaming audience. It's nice to see a developer be so involved and so committed to its gamers. I wish you much success with HellRaid, it's all my friends and I are talking about. We are trying to come up with some hopefully helpful ideas that maybe will considered. Thank you once again for your true commitment to HellRaid's success.

Oh, and the biggest thing in any game, that without it makes any game boring as hell no matter how great it is otherwise. Enemy and boss variety. If you can easily list all the enemies and bosses in your head without trying, there are too few.

One of the most frustrating things about Bioshock was. Oh a splicer, so it's a guy with a weapon and power depending. Different splicers = different guys different load out, ok sure. That's all there was though, all just men with different weapons.
Even Skyrim had a boring amount of enemy types. Again, something Dark Souls did right, tons of different bosses, different enemy types, good. All very very different too. Aim for that or more. The premise of this game looks excellent, and I've been following it closely for quite some time. All too often developers go with the safe approach and don't take 'big risks' although that's not what it ends up amounting to. You guys really have the chance to change the industry and become wildly successful from it at the same time. Do us proud, exceed expectations. Loving the community input being taken seriously. Great job so far, much respect here, and I never say that.

Looks great, has there been any clue as to a planned release date? Even a quarter or some such perhaps?

As far as the specific question, tactics expected or desired. What about specific tactical maneuvers for the AI. Not literally this but, how the greeks and vikings did things like shield walls, or they backed up to give an impression of retreat and then switched to alternative weapons(such as spears) and charged knocking their enemies down.
Also in the picture shown, what about similar to I believe, that Zulu warrior strategy where they separated to the sides (like a flanking move) but they strongly reinforced the sides 2 3 each if you were against a wall, and then sent the majority of their force down the center at you all at once. I wish I could draw this all out sports marker on a whiteboard style. Definitely look at military tactics in people's that utilized weapons associated with games like this. One of the most powerful historical weapons was I believe the Francisca, a throwing axe that was according to experts quite devastating. It was thrown with such force and the physics involved sent it hurtling with deadly force and the way it worked was so efficient it either removed a limb, struck a deadly blow, or caused significant blunt force damage. It rarely did nothing.

AI and tactics is one area where games should always be beyond unforgiving, they should be impossibly hard given equal power ratings for both sides. Making a game unfair involves imbalance in statistics. Players will always be able to learn to overcome AI, so if you aim for AI that is so difficult it seems like it can't be beaten, you'll probably end up around (Very Hard) instead of impossible. Look at dark souls, people were used to win buttons since the time after 'Nintendo and Sega = Hard' now everything is 'carebear' and 'Nerf'. Be one of those developers that makes things punishingly hard tactically, so we all feel like we really earned it when we eventually win.

i have another QUESTION: what about the armor?? if for example a skeleton wears armor at one part of his body... will then be his whole defense bigger or just at the part of his body where the armor is?? and can you also see this stats about enemies??

and could you make a five minute video of just gameplay without any work on it ..that would be great

Oh yeah and skellies should be able to keep fighting if they have had arms, legs or heads cut off. Always nice to be attacked by crawling legless skellies or headless berserker skellies. Skellies with both arms lopped off should try to bite you with their clicking, champing jaws.

If you hit a skellie really hard, you should be able to knock him into another skellie, and have them both fall down. Then, if you do a power attack on a prone skellie it should become a special 'fatality' strike with some cool animation that finishes them off.

i have a QUESTION: will there be information about the weapons like how much damage it does and how fast it is and tips like if its good agains some enemies but bad against otheres ???

Weapon stats will be displayed in your Invetory.

What really interests me is whether the game will run on 32 bit systems?

We will reveal final system specs closer to the release date. Right now it's too early to say.

when the player knocks down but doesn't kill one the nearest non engaged skeleton should help the other back up,as it wouldn't make sense to let your friend eat dirt while you're just standing there taunting the enemy.

enemys should drop weapons once in a blue moon if get hit hard enuf just get there weapons knocked out of there hands and have to pic them up to continue fighting or fleaing

Scott Joy applauds this update, and looks forward to crushing his enemies and driving them before him.

Scott Joy wants enemies to be able to calculate when the odds against them are overwhelming and they attempt to retreat to a more defensible position or even seek reinforcements that Scott joy can also crush and drive before him.

Scott Joy is invincible.

quite nice work there if that all is true what you guys are developing. Is the sneaking system going to rely on shadows or darkness? What about sounds or armor? If I wear heavy armor is the sneaking any more difficult?

Hi devs^^ every thing is all right on your steam page ?

I can see all the hub post be delete or moving !

Can't click on the hub page :(

That mean you prepare the release of the game :D You clean all to get new interface hub^^.

I hope a lot for a released start april, but please, don't make joke the 1st :P

oups, probably steam bug, now i have acces :(

*the aura hammer (left hand) from the bottom and the normal one (in your right hand from the top)

if your special stamina is loaded full you can make things not compared to normal atacking

your warhammer for example starts shining in an misterious turquoise aura (the stone part) and with your other hand you pull an exact copey out of your warhammer made out of this pure aura.

while fighting with two hammers for a short time as your hero move : one aura hammer comes from the bottem and the other from the top and you strike them against each other. then a mighty shockwave is released (that you can also see its turquoise too) and it doeas heavy damage to the enemies in front of you in a 200° arc.

if you dont have enough energy anymore to retain you aura hammer after some time it dissapates fastly

just ideas

That is an with out a doubt, really cool idea. The words on the sword glow lighter the longer you retract an weapon then bam, a powerful strike is released. When your weapon conflicts with the opposing guy's weapon, it creates an epic explosions. And really rare weapons that has an aura of something circling a sword. Also when he unleash a powerful attack. The background noise will tighten and you hear yourself moaning for strength then when you strike. You hear everything normaly and you yell out HAAA! then you hit the enemie and he explodes away.

thank you Wander and i like your ideas too !

you have this ideas by start thinking EPIC

yeah if you special stamina is loaded full and you have a sword

the blade of it starts tearing and out of the letters/symbols on it are getting (not so deep) cracks that now go across your whole blade... out of the cracks is shining holy blue light ,that is full of energy, and it slowly surrounds the blade of your sword

this surrounding light now allows you to cut almost everything with one hit... also full steel armors and stone. it would even do big damage by only touching the sword now, because the light is so powerfull.

while fighting with this sword a short time as your hero move: you take your sword in both hands (blade points to the earth) and you jump in the air high.... while landing (the right leg in front of you and the left behind you) you are ramming your swordblade into the earth and a big crack goes forward alomst 7 meters through the ground and splits it. out of the crack is also shining the holy blue light but high and it does big damage to anyone touching it and the light also splits enemies above the crack like a sword.

when you dont have enough energy anymore the blue light of your blade is shining weaker and weaker and the cracks go the same way back over the blade of your sword right back into the letters/ symbols the started from.

One thing I'd like to see is weaker skeletons reacting to the death of powerful skeletons. They don't need to run or anything, just recoil and gape at the clattering skull.

i think the death of a stronger ally would cause some hesitation in the rest of the skeletons, or if they are of the lowest class, even routing (running away for you non total war people) although if they are....possessed or whatever then that may not be realistic...would be kind of funny though...

the weak scelletons that are the most should just try to atack because they were made for this as their only task but stronger enemies should be clearly more inteligent. They should for example try to get a wizard or a ranger involved in a clode fight because they are normaly range fighter.

The skeletons should laugh like Skeletor.

Stop torturing innocent skeletons! I'm not going to buy this game until a public apology is delivered!!


I suggest that the weaker skeletons would run away and alert the larger groups of enemies, or lure pursuing players into ambushes.

I really like the thought of making the A.I. a huge factor in the gameplay for once in this genre. Usually you'd find an actually competitive A.I. in the fighting genre, but some cheat their way by reading the player's input AS SOON as its pressed, every single time, which is begs the player to exploit through unconventional means.

So I must suggest above all else, if enemies are to be really reactive towards the player's actions (like last minute dodging, blocking, etc), try to make it as human as possible, with the reaction times being similar, if not slightly slower, than a human can react. You can adjust these different reaction times per monster or not to give each of them a different trait about them (I'm indifferent here, but not so indifferent about the whole each type of monster fighting differently of course).

But one thing I'd really enjoy from you guys, is if the A.I. can detect patterns in when a person swings. It's especially difficult to do this in a hack and slash, so I'd imagine that the lesser mobs shouldn't be able to pick up on patterns. But for duals against formidable opponents, I want to see them learn about you, at least a little, so players can attempt to try different ways of approaching them and actually feel intimidated by them even after fighting the same one before (which will increase replayability).

Thanks for the articles about this part of the system. I love to hear stuff like this in a game, and I anticipate more as we approach release.


Things are looking good, can't wait for the game :)

What do I expect from the AI? The lesser intelligent ones should be able to occasionally make bad swings with a sword, a reckless decision, or a misstep.

Some duelists or agile types should do a last minute consciously made dodge, in which they only care for their own survival, so they might crash into others. Also feints come into mind.

Finally some mastermind like wizard/warlock sounds cool, who orders some of his minions into battle (as a trap/bait/misdirection or cannon fodder), made as a well thought tactical decision.

Hey Guys,

Great work, keep it up :) this is becoming one of my favourite games.

with ai will there be a "stealth system" with the player doing the sneaking, I think that also gives some depth to ai since they react to seeing the player in brighter areas and wont see the player until they are reasonably close in darker areas depending on skill.

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