The Limitations of Skeletons [Animation]

Skeletons are great for animating models, but there are times I want to push them beyond what they're capable of...
This same concept applies to many other things as well.

[@cassiebelmont993]

Sakurai overcame the limitations of his own skeleton to play with multiple game controllers simultaneously!

[@competitively3315]

We still need a video showcasing how the fuck he does that. It’s legendary

[@realkingofantarctica]

"From the moment I understood the weakness of my skeleton, it disgusted me. I claimed the strength and certainty of rubber. I aspired to the purity of the blessed squash-and-stretch."

[@RJS2003]

"Your kind cling to your skeletons, as though they will not strain and fail you. One day the rigid biomass you call a temple will stiffen, and you will beg my kind to save you."

[@nicocchi]

and thus you became an ARMS character

[@idiotcube]

@@RJS2003 "But I am already saved. For the toon physics are immortal."

[@YoutubeCommonman_Totas]

BioShock sounding ahh

[@rudeboyspodcast]

I fuckin love Mechanicus, dude. So glad we're getting a sequel

[@BluishGreenPro]

The point Sakurai makes about “IK” being used to make sure characters have their legs connect with the ground is just the start! We’re now seeing IK systems that can procedurally blend unique animations for the whole body as a character climbs their way up a surface. I believe that pushing the fidelity of these systems is quite important; any moment where a character clips into the environment mesh can spoil the immersion of the game’s world; you are reminded that objects have no actual mass or rigidity. Of course, this isn’t something you are likely to notice in the middle of gameplay, and it takes a lot of power to exhaustively compute the collisions necessary to prevent clipping, but perhaps we’ll get there some day.

[@danielcogan8205]

You can see a lot of this in Samus’s movements in Metroid Dread. The way she smoothly runs up slopes and pushes off walls while incorporating the arm cannon’s aim is pretty impressive for the Switch

[@ExploDjinn]

It'd be interesting if they implemented this, but made it more pronounced the less serious a character is. FE doesn't bend at all but Banjo is made of full-on rubber.

[@slot9]

Great video! I was very surprised that you had not found a solution or 'hack' to make donkey kong's arm do what you wanted!

[@YoshiAngemon]

I kinda feel like this sort of tutorial might apply to well-known 3D Modelers like JC Thornton, who applies these cartoonish motions to his animal characters of his original project: The Adventuresome Six, Starring Sean Squirrel, Shauna Squirrel, Cooper Cat, Melville Mouse, Roxanne Rabbit, Chelsea Chipmunk, and their boss bird, Ernest Eagle. I feel that the stretching would look weird when done with a character like Monkey D. Luffy of One Piece, since he IS a rubber man and all. For him, you'd need to have special flexes that generate the body stretching motions correctly.

[@NamePending9]

This is something that famous disney animators have been saying since the very start, you want that squash and stretch.

[@JeffreyThrash]

I’m glad that morph targets (or Blend Shapes, depending on the software you use) exist now, allowing me to push beyond what is possible with mere CG bones. I don’t know how many games actually use it, although I’ve heard the Jak and Daxter and the first Sly Cooper actually used morph targets for both more expressive faces and optimizing the rig to run on PS2 hardware. As Sakurai mentioned here, too many bones is actually bad for game optimization.

[@escargoat8552]

No, this is not squash and stretch. Squash and stretch is about the volume of a character. People need to stop throwing around animation terms when they don't know what they mean.

[@NamePending9]

@@escargoat8552 Its more about the mentality, animating something "realistically" is boring, and you can add more flavour by not having rigid skeletons or by changing the volume of a character. Both are trying to achieve the same outcome.

[@Gnarfledarf]

This information will be useful for the skeleton war.

[@lastnamefirstname8655]

great insight and wisdom, thanks sakurai!

[@Deeheeheee]

But mr sakurai, I’ll break my bones if I do that!

[@qw2_yt]

You know how in IK you have a "pole" bone that determines which direction an arm will bend? I'm thinking this problem is solved if you think of the limb's joints as points on a bezier curve, and then add an "extension" joint past the hand, where moving said joint would bend the elbow region without having to impact the hand or shoulder position. Obviously with this method it will require extra effort AND a working real-time IK system to implement real-time and so you'd rather bake the animation, but if you do that you'd have to re-bake all the animations you'd want to change... And with smash being a fighting game that could be very expensive Someone who works in industry probably would have a better/cheaper solution but that's what I came up with Edit: someone mentioned aux/twist bones which is pretty much better than what i was talking about. you learn something new every day

[@hollowbasket]

Surpass your limits, Skeletons!

[@Brods11]

Excellent info👍

[@ThomatoSauce]

Limitations like this are why I appreciate Body-Breaking & Squash-and-Stretch animation styles.

[@frederiknielsen1688]

"Wouldn't it be fun if we break Donkey Kongs arm"

[@Peter_Siri]

it would

[@andrewpotts]

No more throwing barrels for you

[@BJGvideos]

--K. Rool

[@mylescorley1978]

⁠​⁠@@BJGvideostranslation: -Q. Steering wheel

[@Unit102ALPHA]

TFS Android 18- "I'm gonna break his arm."

[@kuromiLayfe]

This is where Aux bones/Twist bones come in, pretty much extra bones that can offset the position and or roll slightly further than the FK/IK can by default.

[@Blackerer]

2:08 You mean this section of the video talking about it?

[@YerkDiff]

out of all the outstanding achievements Sakurai was able to pull off for Smash Ultimate, I’m surprised bendy bones was where he drew the line

[@ConcavePgons]

The Switch could definitely do it, but not at 60fps with up to 8 fighters on screen. Bones have processing costs.

[@someobscuremusicchannel]

@@ConcavePgons Is that really true? Bending a bone in a different direction would cause performance to tank?

[@aquafox4048]

​@@someobscuremusicchannelfor the switch? I wouldn't doubt it

[@KitsuneFaroe]

​@@someobscuremusicchannelThe thing is bones are hardcoded, to be more efficient, so trying to bend the bone beyond what it is capable by default would probably mean break and rebuild the entire skeleton on the fly.

[@danielcogan8205]

You can do cartoon movements on Switch, but I imagine Smash had some _very_ strict performance requirements. Ever see those old videos where people used a bug with Isabelle to summon like 20+ Rathalos on screen at once and the game somehow handled it just fine?

[@Schimnesthai]

I can't believe mr Sakurai is telling me to break my bones in order to achieve greater expressions in my acting career.

[@NedurFrog3D]

it's crazy how Sakurai is mainly a game designer but still have knowledges on other area of the industry

[@Toniz_exe]

It's crazy but super-convenient as a game designer, it makes communication with coworkers easier!

[@ashenbonfire]

Its kinda his job as a director to be able to communicate effectively with his entire team, and be able to push feedback and stepping-stone improvements back and forth up the pipeline to get to the end goal of the vision being realized. "Game design" is a very multi-hat job, particularly if you're working in indies, or near the top of the chain in a company setting.

[@sebc255]

Game design courses will usually teach you to know at least a little bit of everything.

[@corbinmoore96]

when you're the lead producer I'm sure you pick up a lot of things surrounding the trade

[@eltiolavara9]

it's almost as if he was a director

[@MicaiahBaron]

That is a horrifying DK arm. I love it.

[@spindash64]

Expand Range of Motion

[@jellycore1316]

​@@spindash64XD Perfect

[@PhilipMurphyExtra]

Great episode of gaming with bones

[@LegamSSF]

ZZZ is probably the most recent example of "pushing it further" with its skeletons / character models, especially with its cutscenes. Of course there are moments where the animation seems way too exaggerated for the scene (perhaps this is the issue of the English dubbing, maybe the Chinese/Japanese dub aligns their acting with the movement on screen), but it's undoubtedly such a lively game all around. Kind of refreshing to see a game on a "AAA" budget tackle cartoonish CG.

[@joelsandberg5494]

Now that we know the skeletons' weakness, maybe we can finally defeat them.

[@EdKolis]

Inside you is a very spooky skeleton! You must defeat it to claim your true power.

[@chubchib8638]

I, too, wish to break the limitations of my own skeleton

[@blueheart9873]

Meanwhile Kazuya's forward+up normal attack (Hell Sweep) makes him bend his spine over 360°

[@mmking9999]

Hell Sweep! I was thinking about that move while watching this vid.

[@eyeguydojima7131]

Thats been in Tekken since the first game. It'd be weird if it was changed at this point. So, respect for going out of their way to keep it intact.

[@DANNY1TDM]

IN MY EXPERIENCE,AT LEAST,IK IS USUALLY KEPT TO THE LIMBS

[@BronzeAgePepper]

Hellsweep is done from a crouch dash, different move from the triple spin kicks where he goes airborne first. I think both moves still have his infamous, noticeable elastic spine animation, an old product of trying to "sell" the power of what is supposed to be a really difficult and impractical kick in real martial arts.

[@pelicano1987]

Oh God, in 50 seconds Sakurai-san explained FK and IK in a way I finally understood after many, many months.

[@Belbecat]

It may sound silly on paper, but I'll always remember seeing how much they make Link twist when he's doing an air side dodge and how bloody cool it looked.

[@nicnacs9779]

Love seeing Sakurai making videos like this and showing the joys/challenges of gaming. I'm sure stuff like this will help inspire others to explore creative ways of designing games

[@Goldmight]

Safe to say arc system works are kings of stylistic 3D animation that breaks the norm

[@CyberDragon10K]

All the BTS stuff is fascinating to see how they need to break their modeling in order to achieve one _specific_ look from one _specific_ angle. Among other things.

[@Zant5976]

​@@CyberDragon10Ktheir rigs look like nightmares to work with, but the finished product speaks for itself.

[@goranisacson2502]

If Sakurai could one day achieve the same for Smash without necessarily aping ArcSys's anine style, and for 8 characters simultaneously on a very large stage with lots of other objects... that day, we shall reach Gaming Nirvana.

[@BronzeAgePepper]

​@@goranisacson2502 if that's even possible for a game like Smash, Sakurai will have long left the industry by the time the technology catches up to that vision. Smash has too much else going on beyond 1v1 anime fights that such a painstaking method of animation is feasible in the modern development cycle. It'd be pretty cool though, even if Smash has been in a sort of middle ground between cartoony and realistic ever since Melee, and went slightly more stylized for one game just to aid in visibility on the 3DS's smaller screen.

[@GerardMenvussa]

It seems Sakurai has a bone to pick with these skeletons...

[@23Puck666]

This lesson is so important, my biggest fear is to lose my creativity and ability to innovate!

[@Chadius]

1:14 I think that's the longest time we've heard that BGM...

[@Moegivesmelife]

It's went on for that long in several earlier videos as well!

[@nand3kudasai]

Crash bandicoot doesnt use a bone system (during runtime) as an optimization without which it couldn't run. That's how and why they do so much bending (which looks amazing). (Afaik, theres a cool interview on youtube about the tech tricks theyve used)

[@YoutubeCommonman_Totas]

Sakurai is sounding more and more like a BioShock boss

[@JorgeLopez-qj8pu]

Always has been, remember when he Andrew Ryaned the cutscene trees, destroying them all vowing no one gets to enjoy them.

[@YoutubeCommonman_Totas]

​@@JorgeLopez-qj8pu well yeah, but you're making this unfun

[@fuyukaidesu1641]

I've read a paper somewhat related to that a few years ago, it was "The cartoon animation filter" by Jue Wang et al. You can easily find a youtube video on that. It works by post-processing the animation curves, treating it as a signal and applying a convolution to create exaggerations. I did an implementation on a 3D vocaloid dance and it worked ok, it wasn't really good either, but it did have the "bend the joint the other way" effect when the signal processing is applied over quaternions. Though I guess automated animation post-processing has come a long way in 18 years since that paper. I wonder how much research has been done since then, and how much is published.

[@RebelliousTreecko]

Sakurai channeling his inner octopus.

[@gamefreakDX]

It's pretty easy to see 'Breaking the Limb' techniques in 2D animation because strictly focusing on key poses and the like can only do so much, thought it'll at least look good normally. It's sorta rarer or harder to see with 3D, but whenever it does happen, it's always seemed to be met with 'was that an animation error?' I remember when Overwatch animations first went online and people complained about these stretchy arms and it's just like... what? It's just exaggeration and breaking limbs for animation.

[@JeffreyThrash]

I read an interview on Animation World Network from Hotel Transylvania director Genndy Tartavosky (who of course also made things like Dexter’s Lab, Samurai Jack and Primal) and was shocked to learn that, until Sony Animation pushed the boundaries with Cloudy with a Chance of Meatballs and the Hotel Transylvania series, it was apparently considered bad practice in the CG animation industry to do the sort ot “cartoon-y” squash and stretch we’ve long seen in 2D animation. Personally, I think CG animation is far better off now that cartoon-y timing and squash and stretch is the norm. Not a huge fan of gacha games, but I think Zenless Zone Zero particularly benefits from bouncier animation.

[@_Just_Another_Guy]

​@@JeffreyThrash To me, the first Shrek movie looks somewhat stiff compared to the rest of the Shrek movies that released after it. I think the first Shrek didn't have so much squash-and-stretch animations (at least for the humanoid characters) which is what makes it look a bit stiff to me. Same goes for the first Toy Story movie although the rigid animations in that one worked in their favour because they were supposed to be kids' toys so their limbs were posable at severe angles, especially Buzz.

[@JeffreyThrash]

@@_Just_Another_Guy Exactly. The very first Toy Story in 1995 also gets points for working with the limitations of the time in general. Squash and stretch also pretty much happens all the time in real life, too, it's not like the VFX in Marvel movies or other big-budget mostly live-action movies (or ultra-realistic PS5 games) gets a pass from adding some form of squash-and-stretch animation just because live action generally needs to be more subtle about everything.

[@animatrix1490]

⁠@@JeffreyThrash And in some instances, like with humans’ mouths and foreheads, they look way closer to “real” if you actually push that deformation far enough to get it “right.” I hate the overall design (especially creature design) in Callisto Protocol, but near the beginning when they’re surgically inserting a device into the main character guy, his painful expressions on his face look pretty good because you can see how much his face is contorting

[@JustJustin.]

This video couldn't have had more perfect timing. I'm currently working on a project that involves a character without skeletal limitations. Nice to see encouragement from Daddy Sakurai himself!

[@captainphoton1693]

À good way to implement bones that can bend in Ani directions without looking wierd is to have the limbs and other body parts caged in bones. You have the main one in the middle. And every joing is linked to 4 perpendicular cardinal bones. Then like thoses cardinals with bones from joint to joint and you get a cage around the limb. Weight paint the skin to follow the cage bones. And the middle one is just there to move the cage. There are simple way of making it work. But that's the most basic version. You just have to tweak how the cardinals react to both bones in their joints being moved. This let you have less wired elbow déformations. Where it might lose some volume. And if it doesn't work out perfectly. You have access to more bones to do the exact thing that look right. When exporting into the game you might even have a lot of bones that can just be taken out of the equation as they are only here to guide the cage bones. But once the animation is done it might not be need outside of interpolation or real time IK. There is also many way of making a game engine that make it simpler for you to have such a system. Where the bones are very simple. But it move like if there was a cage with some options. And when needed a simple option let you move that cage as you want for a specific animation. And another option let you divide the bone for a single animation to be able to add bends where there shouldn't be bends. Letting you do stretch ands build more power in an animation. The best use cases I've see for that technic tho. Is for character that have extreme movement on cramped places. Like inner legs, butt, shoulders, armpits, and waist. As this technic can be expanded to basicly work as a simpler mulscle simulation. You arnt simulating how skin move on muscle. You are just ringing skin on bones that are in the perfect position to move like if a muscle was under there. For example dorsal muscles and pecs. That extend of the arm puts and are hard to make look right. If you have a bone there that simulate how it looks it's much easier with less polygons and less texture stretch.

[@GamerFunOriginallyAarush]

Now that’s some great animation!

[@zarfa-de1266]

Bones

[@Scorpey]

So true bestie

[@DarkBloodbane]

Thanks for sharing this Mr Sakurai! I thought it was about skeleton animation but turns out it's about pushing beyond limits.

[@JeffreyThrash]

I think he did a more general video in the past about the need to exaggerate and over-act with CG animation to avoid your characters looking like stiff mannequins, using Clock Tower 3’s over-the-top animation as an example. I still agree with that video.

[@cyberrb25]

That sudden cut around 0:16...

[@BeeBN]

doesn't "vertex animation" kind of fix this? its a feature in blender

[@Koushakur]

1:24 But... joints have no such limits? You might want or need to limit them to 180 degrees for a variety of reasons (like the IK rig bending it in unwanted ways), but they're not "naturally" limited by anything

[@aortaplatinum]

I never thought I'd hear the Kirby guy talking about inverse kinematics. Hotel Transylvania found a solution to this in simply ignoring rigging [at least for the Mummy character] and instead morphing and moving groups of vertices into the desired position, letting him do insane things like change the shape of his entire body with appropriate cartoony squash and stretch. It took a lot longer but the results speak for themselves.

[@BobRod-mi8rq]

Wow, it's like the human body. I think that's disgusting But I guess everybody has learned about the human body eventually 😯😯😯😯😊😊😊😊

[@Nekotaku_TV]

I've become familiar with this sort of thing after having worked in Blender and being a VRChatter.

[@someobscuremusicchannel]

Yee

[@ng65gaming]

Thank you for spreading some actually really helpful and real animation advice

[@RPG_Guy-fx8ns]

"One problem we've yet to solve" ... Use an IK- FK switch. Slaps should be done with FK. Or if you want to use IK, add an extra jiggle bone to the elbow. Or maybe if you want a great solution, script your IK-FK system with physics springs, so updating the IK at high speed, doesn't teleport the FK, it controls it with spring forces and conservation momentum. This isn't a limitation of skeletons, its a limitation of your specific implementation of Inverse Kinematics or a limitation of your specific character rig.

[@CymruCreator]

you could have two skeletons. animate IK on one skeleton, then use that data to control the second skeleton, then manually adjust your offsets on that second skeleton. skin your character using the second skeleton.

[@Vectivus.]

1:46 my arm naturally does that. Most people say it's disgusting but I actually like it.

[@JTolmar]

You can get past the limits of skeletons using cage transforms (see Pixar's old Harmonic Coordinates paper) and get around the annoyance of working with cage transforms by controlling the cages with skeletons. Then you can leave the cages in a neutral pose relative to the skeleton until you need an extreme pose, then use both together to go beyond the limits. This also allows per-limb squash and stretch.

[@NameNotNeeded]

That may partly be why Arc System Works have their 3D models break the skeletons far more often: because they're literally animating by key frames rather than interpretation. Breaking the joints is generally an actual problem that has to be avoided due to bugging the entire animation cycle.

[@TKnightcrawler]

So this was never solved for Smash, huh? That's too bad. I can understand why you wanted to do it.

[@connordarvall8482]

Bending a character beyond what is natural from their model has been a staple in animation for decades. it's where the infamous "smear frames" came from and the 3D animation industry is starting to realise their usefulness.

[@_fudgepop01]

Would it be possible to have a toggle for the bones that line up with the Animation Command systems from older games? Maybe the animator could turn it on or off at certain points for certain bones and generate code to reflect that in-game as a sort of metadata for each attack 😮

[@Polmo1997]

Sportsmate in Switch Sport use 2 additional bones on their arms to do more cartoony and stretches poses

[@shawnheatherly]

You always need to let realism get bent a bit for the sake of fun in games.

[@wanderlustwarrior]

Nobody show him a slowed down pitching motion!

[@ajbXYZcool]

I can definitely see, as a mathematician, how expanding the range of joints would interfere with calculations what with the range of the inverse trig functions.

[@Shadowotd]

Brilliant video about animations so informative

[@TheRealBatabii]

Props to the person who drew those goofy contortionists

[@Amonimus]

Or you can disable the skeleton snap temporarily and rotate the limb manually.

[@flavioalbatrozz2557]

Ed boon should watch this vídeo 😂😂😂

[@AlphaOblivion7]

Don't let Chara see this

[@ShinChara]

Too late.

[@contentdesignwizardry2458]

you are right.

[@RH0660]

Cool!

[@IvanTheBikerFromSpace]

fofo

[@gustinex]

"Pushing beyond common sense is what gives animation its greatness." Just like how booba physics works in games. They defy gravity but dang its great

[@ElTaitronAnim]

I agree

[@Schimnesthai]

I totally agree with the last statement, atleast in my channel i have felt comfort in what i'm doing, but i believe that i have to change it constantly, and i have done small changes multiple times, now i even resent a bit the idea of doing "series".

[@candiiheartss625]

Sakurai is my favorite human from nintendo

[@TheHylianBatman]

Sakurai wants us to start breaking bones!

[@vittosphonecollection57289]

Super Smaaaash BROOOOOOOOSSSSS

[@masterofdoom5000]

Oh I thought this was an upload from a necromancer, my apologies. Neat information though!

[@kotlolish]

As someone who went into blender recently... I will say this.. I prefer having a skeleton yes, but I will have most bones in off set so they can move freely.

[@seele_verloren]

[@luckykaaby1629]

💖

[@Buphido]

Wow, I just got out of an oral exam on that exact topic! xD Amazing timing!

[@jackchong5324]

Thank you Sakurai-sama! These are always so insightful.

[@fernandobignardi6716]

Would Blender IK mixed with Bendy Bones work?

[@DestinySeeks]

The new game by miHoYo Zenless Zone Zero has a lot of exaggerated motion in its cutscenes that give the characters more life and personality, It’s a very stylised look and I really like the look of it. As much as games have been moving towards more and more realistic motion and characters, they come with more subdued expression as exaggerating too much will make it seem uncanny, while less realistic artstyles can fully utilise squash and stretch and not be bound by realism. A good game doesn’t need to have AAA graphics.

[@TuangDheandhanoo]

I did master degree in Computer Art. Took alot of classes in animation... I just understand IK today after saw that 20 seconds part of the video... I wish I saw this when I was in school

[@milesfarber]

I wish more game engines supported IK's. Only Blender does so far, and it's not even a game engine, Godot, Unreal Engine, Unity all claim to support IK but they actually don't, and they're never held accountable for false advertisement.

[@ricthething]

Blender at one point had a built-in game engine, but it became deprecated and it was removed

[@Melody-qf5oy]

Why aren't discretional limitations a thing? A software solution that says; "typical joints don't go this direction, but they can if enough force" seems pretty straightforward to me ...

[@kingnull2697]

It's something you only want situationally If a major characters' elbows bent backwards every time he caught a heavy object, players might notice & its' one of those things you just can't unsee. It's a little like the uncanny valley.

[@Micdades]

Behind the scenes of ExpandDong

[@GraceofGod247]

🎉🎉🎉🎉🎉🎉🎉

[@DGFTardin]

Poor DK

[@Howardpower679]

Sonic team PLEASE understand this

[@budgetcoinhunter]

He's using the Octahedron bone style that's common in Blender... this man knows _exactly_ what he's doing.

[@LuigiTheMetal64]

A male skeleton and a female skeleton are important so the characters would have their own animations to tell apart.

[@mercianthane2503]

I always wondered: Sakurai is right now a Game Designer, but from what degree did he graduate from? He obviously had to acquire some knowledge about 3D modelling, rigging, and other things that game designers needed.

[@obtheair]

Donkey Kong maybe a good example for this lesson, but for me, the best example is Dhalsim.

[@Gnarfledarf]

*may be

[@SolitasRuisu]

This is a really timely episode considering Zenless Zone Zero

[@AntiVectorTV]

I wonder if Zenless Zone Zero is what got him thinking about this. Hoyoverse in general are *masters* of this concept!

[@annieabsorbsaqua5793]

Once again reminded that I hate Blender

[@LuigiTheMetal64]

Sprite characters really have no limits since they can be stacked or be like anime character cels scanned into png images. That is how Ayumi Tachibana would appear as a Spirit in SumaBura Special as the artwork during the production can be found from the 1989 Famicom Magazine's Beautiful Girl Chara Contest. Mr. Game & Watch can be a sprite-based character as he is a 2D model than a 3D model.

[@valeriob36]

Mr Game and Watch does utilize a 3d model (in Smash Bros), but it is replaced by a 2d model if you enter photo mode. The easiest way to see it is during Terry's final smash.

[@Eichro]

Hello, after recent events on a certain local tournament, I'd like to suggest that in the next Smash game Sonic's down B be replaced by Megaman's Metal Blade. Thanks.