Invisible Bunnies That Power World of Warcraft (2017)

https://kotaku.com/the-invisible-bunnies-that-power-world-of-warcraft-1791576630

by cpeterso • 3 years ago

123 100 3 years ago

Reminds me of how, for a very long time, almost every effect in league of legends was invisible minion(s) under the hood: https://technology.riotgames.com/news/taxonomy-tech-debt

tetris11• 3 years ago

the more interesting article is linked in the first paragraph, where spectral kittens power radio stations in Fallout 4

TeMPOraL11• 3 years ago

“The cat acts like a settlement radio receiver, and its role is to keep alive the inactive radio station so it continues to the next track even if you’re listening to another station. Just like if it was a settlement receiver somewhere near the player. In normal circumstances the cat doesn’t make sound. It is silenced, it is invisible, and it is deleted from the game world after three seconds.”

What I don't understand there is, why are those cats deleted after 3 seconds? Does it mean the inactive radio station only continues playing the next track for 3 seconds, and then freezes? If so, that sounds like an unfortunate limitation.

actionfromafar• 3 years ago

Probably a cat needs to press next, but then the cat doesn't need to listen to the full track?

SeanAnderson• 3 years ago

I think the prevalence of these sorts of issues is why ECS is such an appealing architecture in game design. OOP seems to always devolve. A new feature is needed for the game, the feature breaks some well established design rule, it's challenging/slow to refactor everything to make sense while considering the new feature, and so a kludge is implemented where existing objects are forced to be more flexible than planned.

Of course, this can happen with ECS, too, but it feels easier to avoid. Systems which are coupled to individual components of entities, rather than whole objects, provide an extreme degree of flexibility as long as the components stay small.

(bonus: another example of this occurring in Fallout 3 - https://www.pcgamer.com/heres-whats-happening-inside-fallout...)

baq3• 3 years ago

ECS is IMHO a logical consequence of observing that game worlds are not object oriented (as it is taught in schools, so class hierarchies etc.) Add a sprinkle of performance requirements and you get what is understood as ECS frameworks.

…but it turns out that the ‘world is not made of class hierarchies’ observation is not limited to games, hence Rust’s and go’s approaches to OOP: ditch inheritance at the language level.

dale_glass• 3 years ago

The world isn't, but some things are. Doesn't Rust have a problem with GUI frameworks because they heavily use inheritance?

seanalltogether• 3 years ago

ECS makes sense in games because OOP enforces lots of rules downstream in your inheritors, which is good for GUIs, but bad for games when producers keep asking for that one npc or boss to do something special that breaks the rules. ECS is just so much more flexible which is good for some design systems and bad for others.

adr1an• 3 years ago

I had to look that up. From Wikipedia: Entity component system (ECS) is a software architectural pattern mostly used in video game development for the representation of game world objects. An ECS comprises entities composed from components of data, with systems which operate on entities' components.

ECS follows the principle of composition over inheritance, meaning that every entity is defined not by a type hierarchy, but by the components that are associated with it. Systems act globally over all entities which have the required components.

DeathArrow2• 3 years ago

ECS is a kind of Data Oriented Programming / Data Oriented Design. In Data Oriented Programming data and code are separated (no encapsulation). This makes changes much easier to do and helps a lot with managing state.

jvanderbot2• 3 years ago

For what it's worth, I'm not aware of anyone who believes inheritance "ontologies" was a good idea, nowadays. Interfaces sure, but composition is just better for this reason. ECS is a formalization of that, and probably even perpetuated the idea, but it's everywhere I look now.

ramses0• 3 years ago

Since ~2007: https://blog.berniesumption.com/software/inheritance-is-evil...

Jedi "has dark powers", not Jedi "is dark jedi".

That way R2D2 can "has dark powers", as well as can "has light powers".

huytersd• 3 years ago

Sounds like it would have the same problems during refactoring if many different entities relied on the same data. You would have to make sure none of the entities’ behavior changes when you’re modifying your data. It also sounds very verbose where you have to compose each entity all over again instead of inheriting and adding an additional property. But that being said, I would take being verbose over weird hidden layers of abstraction any day.

Coder19965• 3 years ago

That just sounds like OOP but without subclassing.

Coder19965• 3 years ago

I asked ChatGPT 4 for an explanation and came up with this analogy,

Imagine all in-game characters have their data in a database. The database might have one or more tables representing an objects ID or another reference, its position, its health points, and image data representing how to draw the object. These three things are "components" and the IDs and references are "entities."

A system is anything that manipulates one of these components. Thus, a function that manipulates a component is a system.

TeMPOraL11• 3 years ago

Ah, ECS. The most ill-defined software pattern since IoC/DI. Everyone seems to have their own understanding of it, usually somewhere on the spectrum between "what if we kept the game state in a relational database"[0] and "what if we put any individual type of information into its own big array, so it's CPU-cache-friendly"[1]. I wrote several such systems for my own toy games, at various points of that spectrum[2], and I still have a bunch of open questions I can't seem to get my head around.

The biggest such question is: how the hell do you handle "cross-cutting concerns" in an ECS architecture, especially in the data-oriented programming version, where "cross-cutting concerns" are basically any kind of logic ("system") that needs to access more than one component of an entity at the time, especially if it does so conditionally? Like e.g.:

- Physics, rendering, animation, and game logic all need to access some subset of the same position, orientation, dimensions, velocity, acceleration, mass, tensor of inertia, etc.

- Any kind of logic that goes like "IF something(component 1) THEN doSomethingTo(component 2) ELSE doSomethingTo(component 3)".

How are you supposed to preserve data locality in such cases? Is it even theoretically possible?

I may have some fundamental misunderstanding about the definitions here[3], but I haven't found any clear answer to the questions above, whether theoretical or practical. Back when I last looked, couple years ago, I couldn't find any non-toy game written ECS-first and with source available to study. Maybe this has changed now.

[0] - Which, as far I recall, was the original idea behind the pattern. It's also a very interesting one in general - if you squint, a lot of code all of us write for our projects is just half-baked attempts at setting up specific indexes and hand-rolling queries to a bunch of vectors, hashmaps, or (gasp) object graphs.

[1] - AKA "data-oriented programming", in this case mostly preferring "Structs of Arrays" over "Arrays of Structs".

[2] - One of them was literally just "let's store all game state in an in-memory SQLite database, because guess what, it's actually fast enough to be queried at 60 FPS!".

[3] - In my defense, most of the guides, tutorials and articles I read back in the day were themselves confused between "SQL approach" and "SoA approach" (see [0]), or worse, mixed in "whatever abomination Unity passed as ECS back then" and even something semi-related from .NET world. It took me a lot of time to understand that everyone's using their own blend of all those ideas, and this left me unsure about what one's really supposed to do.

Joking_Phantom• 3 years ago

I think the answer is that ECS isn't supposed to solve those problems directly. It's just a framework that makes a certain class of problems very easy to solve. But big picture complexity is still up to the developer's skill and wisdom. Knowing which parts of the game should go into ECS, and which parts go somewhere else. Which systems flow from another system. Which system is allowed to manipulate the data directly and which systems are only able to read data reasonably, but not write. And how your design of the game may need to change to suit the limitations of your computer and your ability to program.

ECS is like any other framework. It is a tool or system, for organizing your efforts. Be very liberal with using it in its intended scope. Be judicious when its at the edge of its scope. Be very skeptical when its outside of its scope.

katzenversteher• 3 years ago

I believe Space Station 14 is implemented using an ECS engine. It's open source but quite impressive regarding scale and features. It's also a multiplayer game which brings some extra questions to the usual ECS ambiguities.

ajuc2• 3 years ago

Any kind of logic that goes like "IF something(component 1) THEN doSomethingTo(component 2) ELSE doSomethingTo(component 3)"

What's the problem here? You write a system that queries these 3 components and then call regular functions. In bevy (a rust ECS framework) it would look sth like this:

    fn complex_system(
      query: Query<(&Component1, &Component2, &Component3)>,
     ) {
      for (c1, c2, c3) in query.iter() {
         if condition(c1) {
           doSomethingTo(c2);
         } else {
           doSomethingTo(c3);
         }
      }
     }

I think there's no need to deconstruct everything into smallest possible systems, this level of granularity is ok. You could also make the condition into something that can be selected by the query and remove the if.

    fn complex_system2(
      query: Query<&Component2, With<ConditionFullfiled>>,
     ) {
      for c2 in query.iter() {
           doSomethingTo(c2);
      }
     }
     fn complex_system3(
      query: Query<&Component3, Without<ConditionFullfiled>>,
     ) {
      for c3 in query.iter() {
           doSomethingTo(c3);
      }
     }

But that's only possible if you can make the condition be simply existence of some component in given entity. Could be improved with systems that query based on values of components and indexing could be added, of course, but I haven't seen that kind of ECS yet).

octavius__2• 3 years ago

Physics, rendering, animation, and game logic all need to access some subset of the same position, orientation, dimensions, velocity, acceleration, mass, tensor of inertia, etc.

I wish I knew the solution to this exact problem. IMO this is the central issue that stops pure ECS from being useful.

bob1029• 3 years ago

Thank you for this. I've been waffling on just using SQLite to store all the game state. I will give it a shot. I know it will break down for larger scenes, but I don't think I have those yet. Simplicity is probably way more important than anything else for a solo dev custom engine experience.

Joker_vD• 3 years ago

As for your DB remarks, I've recently read an interesting blog post [1] about using SQLite as a cache in the context of web frontend. Apparently it works Well Enough™.

[1] https://sqlsync.dev/posts/stop-building-databases/

deadbabe3• 3 years ago

You seem to have deep fundamental misunderstandings about ECS systems.

You can absolutely access multiple components in a system, for some reason you think a component and a system must have a one to one relationship, when really it’s many to many.

The only caveat is that you have to think carefully about the order that some of your systems are executing in the game loop, since you want to make sure component data has been updated appropriately for later systems to act on.

ECS is really the best way to make games. It lends itself well to rapid iteration and experimentation of new game concepts.

octavius__2• 3 years ago

Another recent example is from Starfield, where shops inventories are handled by a physical chest hidden underneath the shop. You can use noclip to loot the chest and get shop items for free.

TeMPOraL11• 3 years ago

That kind of makes logical sense, though. Physical hidden chests are, after all, how almost all real life shops implement inventories. Those are typically inaccessible to players, too.

(There is a part of shopping experience where the player grabs items and puts them in their own chest/basket prior to purchase. This works thanks to the security scheme of law enforcement NPCs dragging your ass to jail you can't save-scum your way off, should you steal something. But this is too complex to implement in a game, unless you're making the next GTA.)

Hell, even the bunnies and spectral radio cats make sense, to a degree. This reminds me of the ol' Flash games or Klik&Play/The Games Factory-made games. In all of them, you'd find yourself placing support objects on the scene but outside the screen boundary. I used to laugh at it, but eventually realized it kind of makes sense, if you think of the game as a theatre play - there's lots going on at the edges of the stage, just beyond what the audience can see.

Or think back to RAD tools from Borland (Delphi, C++ Builder) - they had a notion of abstract objects like "Timer" as invisible UI controls that could be placed in the window you're designing. On the one hand, this makes no sense - an abstract timer doesn't have "position" or "size", not at runtime. On the other hand, it was intuitive and convenient at design time.

delecti4• 3 years ago

That's been the case with Creation Engine games for decades, it's also present in Oblivion, Skyrim, and Fallouts 3/4 (and maybe others, that's just all I have experience with). It's amusing that it still works the same even through the iteration of the engine they made for Starfield.

alex_lav• 3 years ago

(Off topic to ECS) This description is kind of funny to me. If you’re using noclip, who cares about how much things cost? You’re already cheating.

sdwvit2• 3 years ago

Been like this since at least Skyrim, maybe earlier

jerf• 3 years ago

I'm not really sure this is an OO vs. ECS vs. any other design architecture thing, as evidenced by a lot of your other replies. I think it's just a general programming pattern that it's very tempting to take a large dependency on in order to get some small bit of functionality. Then, Hyrum's Law takes over [1], and you end up with a few more bits of dependency on the massive bit of code you pulled in. And you pull in a few more massive dependencies for just little bits of functionality, and organically grow a few more attachments to the huge code base. And before you know it, you've got 10 massive dependencies, and you only use vanishing fractions of their functionality, but extracting any of them is a huge pain.

It's true that OO design pushed game engines in this direction; if you need something that only the last "full on NPC" node in the inheritance tree provides, which is very believable, then your designers are going to use it, even if they don't need most of the rest of what it provides. But I think this is something your designers are generally going to do anyhow. They aren't professional programmers and they aren't sitting there worried about long term code quality (especially not in the games industry), they are worried about getting their job done, and under any design it's going to be easier for them to reach for a large stick and pare it down than to reach for the small stick and then laboriously figure out how to attach the extra bit it needs. It doesn't matter how easy it is to attach the extra bit, it's going to be easier for them to grab the big, all-in-one provider. They're going to figure they may need the other stuff later anyhow, and they're reasonably likely to be right so it's hard to even call that irrational.

You can see this pattern all over in programming. I know of multiple codebases where I work that suffer from this pattern without any games being involved. Developers could implement new subsystems either as independent subsystems that they minimally connected into the main product, but have relatively few services provided by default to those subsystems, or they could start from day one fully integrated into the rather massive monolith with all the services it provided, even if it wasn't great with those services. And generally they would choose the latter, making the monolith even larger and the crossing mishmash of dependencies on the large services even bigger and more complicated. Maybe they were even right at the time, but now we've got some fairly large and complicated balls that can't be replaced in a big bang, but also can't hardly be replaced incrementally, because everything depends on everything. Upgrading any portion is a nightmare. They reached for the super complicated, relatively powerful objects that provided all the services even if they just needed a couple things, and now they're all in a spaghetti pile. And there's hardly any OO in sight, this is all really just procedural despite the occasional OO island.

You can see this in the still-growing general understanding in the programming community that dependencies are not free. The benefits you can obtain from a dependency are enormous, immediate, and easy to see. The costs are subtle, to the point that you can be mocked by developers for thinking they even exist (though I see this particular attitude fading, fortunately), but it's easy for them to grow into at least the order-of-magnitude of the benefits, and sometimes exceed them.

[1] https://www.hyrumslaw.com/

wolfendin• 3 years ago

This always became really interesting to see when you had a private server and could view invisible NPCs.

The “bunnies” usually used the default infernal NPC graphic

cedilla• 3 years ago

Are those bunnies leaked or datamined "official" Blizzard bunnies, or where they reimplemented by private server providers?

Vuska• 3 years ago

Datamined probably. Thousands of them can be found in the game files: https://www.wowhead.com/search?q=bunny#npcs

h4kor• 3 years ago

Building custom maps in WarCraft3 also involved a lot of invisible units to create unique spells. Creators generally used toads or sheep for these effects.

I've created a custom map turning the system a round, where you played the invisible critters instead of the hero :D

myfavoritetings• 3 years ago

I wonder if this was the inspiration for the name of the creator of DotA mod, icefrog

Already__Taken• 3 years ago

oh that map was you? I was completely baffled as a kid whatever that map was about

bananamerica6• 3 years ago

Can anyone point to a better source for this so I can't share it with people? Kotaku is the TMZ of gaming and I never share it, but underlying content is good on this article.

delecti4• 3 years ago

This is the original source, reporting on a conversation between the writer and someone involved in the design being described. There can't really be a better source than that. Kotaku's uniquely bad reputation among gaming websites is only a result of people pushing a false agenda.

hnbad2• 3 years ago

Specifically Kotaku's bad reputation primarily stems from GamerGate.

bananamerica6• 3 years ago

I understand that you would think that given the assumed context on this website but I'm not even American and the gamer gate thing was very distant from me, something foreign I read about in the news. I have absolutely no issue with this website's politics or any kind of agenda. Kotaku took a turn for the worse specially after the departure of Jason Schreier. I've read Kotaku for years, and I largely agree with Kotaku's political views and I was never part of any ridiculous gamer gate movement.

It's just a shallow website that is largely made of reposts, low effort sensationalism, poor journalism, and articles that could have been a Tweet. I do not repost it because it is extremely low quality even when it is the original source. But that subject was interesting so I wanted to find another source to share.

jabroni_salad• 3 years ago

I definitely read about this on wowinsider at some point. sadly it has been really annoying to search the stacks since it got turned into just an engadget tag so that AOL could turn their wow.com domain into a failed coupon venture

smcl• 3 years ago

Sometimes you don’t know designers need a kitchen until they’ve made ramen in a flower vase with an iron

Wonderful

DeathArrow2• 3 years ago

OOP at it's finest! I wonder if they have BunnyFactoryFactory.

red_admiral• 3 years ago

Bunnies reproduce just fine without factories :)

stuaxo• 3 years ago

I really need to sort out adblocking on my phone, there are so many half the time it doesn't even show all the content, it's probably ran out of resources.

burke• 3 years ago

Seriously. This was the most abusive reading experience I’ve come across in a while. I also only got to read a couple of paragraphs before endless ads.

toastedwedge• 3 years ago

uBlock Origin on Firefox mobile is enough to not be bothersome. Even if it's not your preferred browser, it could help with ad-riddled sites at least.

nerdile• 3 years ago

For Android, Edge and Opera both have ad blocking built-in. It's comments like these that remind me what I'm (not) missing.

sparrowInHand• 3 years ago

The problem in my opinion is that many game-engines are to focused on the "PerFrame view of the world" statically imagined by the designer and do not architecture for persitent but changing effects or long causal chains that constantly change and are capable of reusing behaviour. Good news though is that most by now, outsource that to scripting languages capable of providing better ways to implement this, but then you end up with parallel implementation of basic behaviour & services like pathfinding or targetting.

Imagine a late-game added lightspell, that is expected to behave like a ball lightning walking ahead of the player. The temptation to reuse the pathfinding, collission and other systems that controll figures will be enormous. But this behaviour needs a sort of CBipedal class to inherit all the behaviours. Voila - enter the hack.

Of course the clean solution would be something like a thrown stone on a lake, it exists as running code only when it changes (certain frames or events). It holds a composition of behaviours without the other ballast (datastructuress for aiming, inventory) etc. and also does not need a pool allocation to the monster/npc pool. (Basically you either have many peasants or many lightballs in the hypothetical as tradeoff).

Cause it aint a object, its a entity with a collection of behaviours, with a minimal data container bound to each behaviour seperatly, that may evaporate at a moments notice, should the player look away or its time run out.

eqvinox• 3 years ago

The only thing that bugs me about this is that they used bunnies rather than making a specific "spell effect/scripting" NPC. (I mean just one type to be used everywhere rather than bunnies, not a new one for each use.)

It's common enough of a pattern in other games, and the #1 bug is that someone forgets to click the "invincible" checkbox somewhere, your scripting 'bunny' dies, and then the game just breaks. If you create a NPC type just for scripting, you can have it default to invincible & invisible (or no model to begin with.)

jimmaswell• 3 years ago

I recall a story where the camera kept "dying" from explosions but I can't find it.

jcalx• 3 years ago

Under "Camera obscura" here: https://www.gamedeveloper.com/design/more-dirty-coding-trick...

alasdair_• 3 years ago

Perhaps the most famous time this happened in an MMO was the assassination of Lord British.

https://en.m.wikipedia.org/wiki/Lord_British

xjay• 3 years ago

The battleground, Strand of the Ancients, was originally started using two invisible NPCs that were hostile to each other; one on each faction's boat and dock. The first boat/NPC to reach the dock would trigger a spell/script when in proximity, starting the first round. [1]

[1] BlizzCon 2016 - WoW Engineering Panel https://www.youtube.com/watch?v=W1y2fdDeSbU&t=227s

VoodooJuJu• 3 years ago

In developing mods for Warcraft 3 using its World Editor, we'd often have to create invisible dummy units for the same reasons, like to cast a spell as part of a more complex custom hero ability. Always felt like a hack, but it's funny, surprising, and validating to learn that Blizzard essentially does the same thing in WoW.

kevdev• 3 years ago

Reminds how in one of the Bethesda Fallout games, they needed a subway train car. Solution? Make an NPC with a train car head that runs really fast.

csours• 3 years ago

Blaine, is that you?

Also, reminds me of the Princess Donut book series.

kemayo• 3 years ago

In a similar vein, WoW has become a lot more dynamic and stateful over the years, and the somewhat-hacky solution used to track what the current character has actually done is invisible quests. It's the exact same system behind the scenes as the more-visible "kill ten rats" quests that NPCs give you, just hidden away so you're not told about them and tracking things like "you've looted this treasure chest in the open-world, so it won't appear for you again" or "you've listened to this ambient NPC conversation".

You can even install an addon that'll show you the quests getting completed in the background, which can occasionally be handy as it basically notifies you "what you just did will be remembered". https://www.curseforge.com/wow/addons/questschanged

Amusingly, these quests still count as completed-quests for the in-game achievement system, so new characters will confusingly get achievements like "10 daily quests completed" despite never having actually completed a visible daily quest.

yett• 3 years ago

Wow thanks for this! I have sometimed wondered how I get 50 quests completed! achievement on a new alt even though I barely did 10 quests

joe-collins• 3 years ago

The burst of quests is, last I checked, mostly stuff about unlocking battle pets and allied races.

omneity• 3 years ago

This feels like a badly implemented homegrown ECS pattern.

ECS is kind of like lisp. Every sufficiently complex game will implement its own bug ridden ECS framework (unless it uses one already)

hutzlibu• 3 years ago

"Why is WoW a front for a morally questionable bunny labor operation? The short version is, programmers’ time is limited, and NPCs’ time is not. Programmer time is extremely valuable, and most of the ‘stuff’ that can be done in a game can be done by NPCs,” said Chapman. “NPCs already have to support things like pathing, casting spells, using weapons, doing various actions to other NPCs, etc. So, while you could in theory have a programmer separately implement every ‘effect’ you wanted in the game with some minor benefit, if you already have a class of thing in a game that can solve your problem, it’s a better use of time to use the existing system.”"

I am sorry, but it still is just bad design, if you have to missuse a different class. So strictly economically speaking yes, after the system was already running, it might have been cheaper to go with it than redesign - but the initial design flaw is still a flaw. But they still made lots of money this flawed system, though, which is a good reminder, that the most important thing for any product is usually, does it work?

TeMPOraL11• 3 years ago

Honestly, I see it as accidentally good design. Take the "laser turret pointer" mentioned earlier. If you're not doing an optics simulation, but engage in the magical thinking (usual in storytelling) and treat the impact point as the entity of interest, then... making the impact point another actor on the scene suddenly makes perfect sense. Between the article and the comments, a lot of things bunnies/spectral cats/minions are known to be used for make perfect sense, and I'd consider explicitly planning for it when designing a new game.

Still:

But they still made lots of money this flawed system, though, which is a good reminder, that the most important thing for any product is usually, does it work?

That is a very good point, especially in videogames/entertainment. Reminds me of the "first law of 3D game graphics" I read somewhere - "if it looks good, it's good - no matter the amount of cheating going on".

sdwvit2• 3 years ago

Invisible creatures have been a hack to make a lot of channeling spells work since Warcraft 3

ben_w• 3 years ago

Back in the day (late 90s), I was heavily into the Marathon series and game engine. The trilogy box set came with a whole bunch of 3rd party levels, including one inspired by Myst. As Marathon was only one step up from Doom and (before getting open sourced and turning into Aleph One) had no actual scripting language, the level creator had to fake lots of things the hard way, one of which was by spawning NPCs to shoot at other NPCs, with weapons whose shots were marked as "can toggle switches" and some switches between shooters and their targets.

alexwasserman• 3 years ago

Reminds me of the subway trains in Fallout 3 being hats on NPCs that walk the track so the trains can move.

Invisible Bunnies That Power World of Warcraft (2017)

Related Stories