Jiggle Physics is the art and science of simulating the behaviour of non-rigid objects and materials in a computer. In this respect, it's a sister trope to Ragdoll Physics, which deals with more rigid structures.
The earliest uses of Jiggle Physics were not for simulating anatomy, but rather for hair and clothing. Of course, once more computing power was available, it was adapted to simulate soft anatomy, such as fat and the example which first comes to mind for most people when they hear the term, breasts.
Next time you play a game or watch an all-CGI movie or cartoon, take a look at what bounces and jiggles in reaction to physical stimuli. Whether it's the Badass Longcoat of the hero bouncing and flapping around as he runs, the gelatinous monster wobbling as it's pumped full of plasma fire, or Ms. Fanservice putting on a (perhaps unintentional) show, there's some pretty clever programming behind it.
For a more low-tech, more specific similar trope, see Gainaxing. Examples from sprite-based games should go there as they do not involve physics computations. Implementing Jiggle Physics almost always means an aversion of No Flow in CGI.
- Batman: Arkham City's Catwoman has this. It's very subtle though.
- Interestingly enough, in the previous game (Batman: Arkham Asylum) Harley Quinn doesn't. Her breasts may as well be encased in hardened cement for all they move, even when she is bouncing and turning and doing acrobatic flips.
- The latest of the Tomb Raider games have it, as would seem obvious. The early games show exactly what is wrong with its absence; Lara's chest is literally Barbie-esque in its steely inflexibility, as if she were smuggling a pair of cannonballs in her bodysuit, or a pair of traffic cones if you played the first game. It was only in the cutscenes for Legend and Anniversary; Underworld has it in the gameplay itself. It's very subtle, but it is there. At least unless you use a user-made Jiggle+ PC mod for Underworld, which approaches Gainaxing.
- In the lastest games, the developers actually used the jiggle physics from Dead or Alive, below, for use in Lara's ponytail.
- Rouge the Bat in Sonic Adventure 2 has this. Yes, they seriously used this on the breasts of a cartoon bat in a kid's video game. The titular protagonist and his Evil Doppelganger have this applied to their quills as well.
- In Okami, wood-sprite Sakuya and priestess Rao both take full advantage of a physics system which was designed to show off everything that can bounce and sway. You know, their hair. (And busts.) While Sakuya is an Innocent Fanservice Girl, Rao is most definitely doing it on purpose.
- Overlord II applies this to the scantily clad fairies, mermaids, and elven priestesses. Who are hideously obese.
- In Scott Pilgrim vs. the World: The Video Game, Ramona, Kim, and most of the non-playable females have breasts that jiggle constantly.
- No More Heroes 2: Desperate Struggle has them. However, instead of just being used for breasts, they are also used for things such as Travis beam katanas dangling from his belts, his jacket, and his hair.
- The Legend of Zelda Skyward Sword has this on Peater. You know. The fat guy. Yeah, him.
- And the Moblins. You know. The ones in thongs. Yeah, them.
- There's also some physics applied to long clothing, such as Link's tunic and hat, and some items, such as the bug net. Pretty everything except for women's breasts jiggle.
- The entire selling point of Lula 3D was the "Bouncin' Boobs Technology" prominently advertised on the cover.
- The Dead or Alive series is known for having it, playing with it, and selling the game with it. An age input on the second title actually determined how much the female fighters could bounce. The older your age, the more they did, up to a point that a 99-year-old man probably wouldn't be able to play without a heart attack. Even while standing still they tend to bounce. A later Spin-Off would bring it further to the forefront by transforming the game into a beach volleyball title and eliminating the male competitors. Their hair is also lovingly animated and streams all over the place as the move. Essentially this is one of Tomonobu Itagaki's defining traits of his games and is also highly prevalent in Ninja Gaiden.
- In the Nintendo 3DS version, shaking the system while viewing collectible figurines of female characters will cause their breasts to bounce in relation to how you shook the system. And to think that originally, Nintendo wasn't going to equip the system with motion control at all...
- The PS4 version of Last Round introduced the soft engine, which gives an even more natural movement. Xtreme 3 further improves on it, accurately simulating movement of skin and tissue as objects are pressed against it instead of clipping.
- Dead or Alive Paradise used an over-the-top version (perhaps trying to out-extreme Xtreme 2?). As commented upon in reviews like GamesRadar's here of egging from Nerf NOW!! here.
- The Soul Calibur series displays this, but it is very much downplayed and almost, dare say, "realistic", at least early on in the series. Still, it has many varying examples.
- The ninja Taki, whose breast movements, while they don't bounce too much, appear to be timed one full second behind the rest of her body.
- Xianghua, though, has buttock jiggle physics. So does Talim, and maybe others.
- Disturbingly enough, Astaroth has a chest that jiggles noticeably whenever his onscreen model moves quickly enough. Eeewww....
- Even more disturbing, Voldo's ass jiggles in Soul Calibur 2. Feel free to introduce your mind's eye to a knife.
- Of course this was all thrown out in Soul Calibur 3, in which all female character with the exception of the underaged Talim have been given larger breasts and costumes that allow these to bounce around in a ridiculous manner, such as when you SELECT them in the character selection bit. Astaroth's chest jiggle is still intact. If you leave the shop while one of the storekeepers is gesturing, their boobs jiggle up at a ridiculous height, and then go back to normal.
- By the time of the fourth game, cover-art character Ivy's move with so much momentum it's stunning the rest of her body doesn't follow them into a knock-out when she stops moving. It's considered part of the package deal, alongside destructible clothing.
- Marvel VS Capcom 3: Fate of Two Worlds goes to town applying this trope to Chun-Li, Morrigan, Felicia and Trish (from Capcom's side), as well as Storm, Phoenix, X-23, and She Hulk (on Marvel's side).
- Since Street Fighter IV is the first game in the series proper to use 3D models, it also added jiggle physics. Disturbingly, the most visible wobbling happens on the morbidly obese male Rufus.
- Smackdown vs. Raw 2011 has this with their divas, in both the breast area, and the buttocks region. And it's great.
- In Lightning Legend Daigo no Daibouken, this is the main animation feature of Misa Atago, the resident busty female character, to the point one's can wonder her breasts manage to stay in those Impossibly Low Neckline clothes with all that bouncing. She's also the only female character having those physics, the other girls being the flat-chested Mayu Uzaka and the young Yuki Shirogane.
- UFC Undisputed has this for the ring girls Ariani and Shandella.
- Bloody Roar: Primal Fury was particularly egregious with this. EVERY character had jiggle physics - the women in obvious places, but the men's biceps would bounce as well. Apparently nothing below the neck was actually connected to the characters' skeletons.
First Person Shooter
- Valve added 'jiggle bones' to their Source Engine. Guess what modders commonly use them for?
- Replacing The Scout's bat with Thor the Giant Horse Dong of Death?  (NSFW)
- Or making the Scout's head use jiggle physics?
- Jigglebones were added to the glove on the Pyro's hat. Considering the Pyro is possibly a girl, that's the closest you'll get to Jiggle Physics on a Team Fortress 2 character. Unless you download one of thecharacter mods that converts Pyro into a girl. Well, a less ambiguous 'girl'.
- Some other hats have also received this treatment since, including the Hustlers Hallmark (a pimp hat for the demoman, only for the feather) and the Pyro Brainslug.
- Even some weapons use the feature, such as, of all things, Jarate.
- Actually, Valve has been using this trope since 1998. In the original Half-Life, the female Black Ops Assassins have exaggerated bouncing boobies.
- Not really "physics" though, as they're part of the animation. Makes it even worse seeing those motions had to be specifically programmed in by the animator.
- Left 4 Dead adds jiggle physics to the Boomer, a extremely bloated zombie whose belly has grown out of the shirt. The sequel adds a female version of the Boomer with similar results in the jiggle. It was also used for Zoey's... ponytail.
- It was used on Chell's... hair.
- Duke Nukem Forever. If it existed in 1996, Duke Nukem 3D would have had it. The technology has finally allowed Duke to enjoy jiggling boobage.
- Halo: Reach has subtle jiggle physics on Spartans' rear ends.
- In Resident Evil 5, Excella jiggles. This is rather disturbing at one part as she is on all fours gasping in pain as her cells get ready to turn into giant leech-slugs.
- In Resident Evil 4, Ashley's breasts do a bit of jiggling, but it's most noticeable while on the elevator. Bizarrely, they're bouncier in the US version than in the Japanese version.
- BloodRayne has it, and even has a cheat code to enable increased boob bouncing. The cheat code is Juggy Dance Squad.
- In Resident Evil: Degeneration, this trope is invoked throughout the movie, seeing as the movie itself was animated using CGI. A noteworthy example takes place near the end of the movie, with Angela's hair swaying quite flamboyantly in the wind, although it should be pointed out that Leon's (and Claire's) hair barely moved in the same scene.
- Averted with the female characters in Dead Rising. Where can Jiggle Physics be found, then? On the manboobs and spare tire gut of Larry, a Fat Bastard boss. One order of Brain Bleach, coming up.
- Every time the player stops running in Haunting Ground, the female protagonist's breasts bounce, despite not doing so when she runs. They also jiggle quite a bit even when she turns around. That, coupled with the convenient close-ups of Fiona's upper torso when she falls, makes the game a big dose of Fan Service.
- Seen in Dragon Quest VIII with the character Jessica. She has enormous boobs, which jiggle and bounce whenever she does anything, several different character models of her in skimpy clothing, and even a skill set called "Sex Appeal". Lampshaded in the game, when her mother chastises her for her choice of revealing traveling apparel.
- The game Vampire: The Masquerade Bloodlines has numerous female models for the player to control, depending on what type of vampire he/she chooses. Oddly, only some of these have jiggle physics - others appear to have breasts made of solid metal. This makes sense, once you consider that the game is set in L.A., and that some of those characters have very tight dresses/tops, whereas others Malkavian are more like a loose band of cloth. The "money" cheat lets you edit size, just in case you needed to check. They developed a version of this technology, and were the ones who coined the term, 'Jiggle Physics'.
- In Final Fantasy X, busty gothic lolita-styled mage Lulu had breasts that moved as if they were filled with water. If you ended a battle with her hasted, they appeared to jump like a prodded frog.
- In Final Fantasy XII, Fran's buttocks do this at several points, most notably when she walks away from other Viera in Eryut Village.
- There are a few cutscenes where Tifa does this in Final Fantasy VII. Justified example - Tifa's infamous knockers were caused by rendering limitations on the PlayStation. The original character was supposed to have B- or C-cup breasts (as seen in concept art), but when the graphics programmers realized the issues at hand, it boiled down to huge knockers, or flat as a board. The team chose the former.
- Ironically, the Bioware RPG game Neverwinter Nights had only a single character model with jiggle physics - a female wearing a bare-shouldered Breast Plate. The armour was solid, but apparently the breasts behind it weren't attached to the woman, or snug against the armour. When fan-content added jiggle physics to other character models, even the most rigid steel full plate armour jiggled like a jelly castle. Most fan-made jiggle mods have boobs that jiggle in the wind. Other than that, A Dance With Rogues Jiggle Physics made a bit of sense (all the outfits the character would likely be wearing were rather...exposed).
- Dragon Age 2 has major Jiggle Physics for the breasts of any female character not wearing plate armor, as well as some longer hair.
- World of Warcraft features jiggle physics. Most female playable-characters in the game have some form of jiggle, but Female Tauren and Trolls have it particuarly blatant - their idle animation has them stand there breathing while their huge boobs bounce up and down like they're busy on a trampoline.
- Judith from Tales of Vesperia is guilty of this. In the Play Station 3 remake, when performing her Second Mystic Arte, her animated-cut shows her hunnies jiggling for about a split-second as she throws her spear. Other few Tales characters, like Sheena from Tales of Symphonia, have it too, but it is not obvious unless you watch them move very carefully and up close.
- Any female character who had a noticeable bust in Agarest Senki 2 did these in HD sprites.
- There is a mod that allows this in The Elder Scrolls IV: Oblivion called 'BBB'.
- Star Ocean: The Last Hope has Myuria, whose breasts wobble all around the place even when she's standing still (as evidenced by the cutscene in which she's first fully revealed). This provides an answer to why Reimi keeps her assets so securely bound in place...
- Done in the first Baten Kaitos game...to Geldoblame's One-Winged Angel form. You will want to rip your eyes out.
- Also done to certain shopkeepers in Origins.
- Shadow Hearts Covenant has Karin bouncing along to jiggle physics when she runs, but it's not her chest, it's her hair. The straps on Yuri's bag also seem to have jiggle bones in them and flap along behind him in response to his movements.
- Vindictus takes full advantage of Valve's physics engine to incorporate some rather... ludicrous movements to that area.
- Spore. Oh god... With the right combination of body parts, anything can jiggle.
- Jiggle Physics were recently added to Second Life as well. As with all things Second Life, it can be manipulated and tweaked to your hearts content to create things that occasionally require Brain Bleach.
- Metal Gear Acid 2 came with a pair of 3D goggles allowing you to see the breasts' undulatory movements in gropeable solidarity. To save time, the developers used the same physics set on the ludicrous ammo pouch Snake wore on his own chest. The effect was...well... Not to mention that Venus, when, getting bored or some else, would hop up and down. WHY, HELLO, THERE. Also, due to how avatars are typically added when a new area is loaded everyone's breasts/ammo pouches would simultaneously, spontaneously bounce up and down. To prevent problems with e.g. someone's feet intersecting/sinking into the ground, they are actually created in the air and allowed to drop a short distance to the ground. Rendering can be delayed a second to hide the drop, but the afterjiggle...
- For some really, really well-done Jiggle Physics, look at EVA from Metal Gear Solid 3. Unless you're paying attention, you won't notice - her breasts move exactly like a real person's. Particularly of note is the scene where, clad in her underwear, she crawls hands and knees towards Snake as part of an attempted seduction, and her breasts actually change shape - again, exactly like a real person's. The irony kicks in when it turns out that the woman has had bust enhancement surgery, which, using the techniques from the timeline she's in, would leave her rock solid. Then again, she probably got secret high tech Chinese PATRIOTS grade honey pot implants with technology not commercially released for decades knowing the series.
- Metal Gear Solid 4 takes this to its logical conclusion with interactive jiggle physics. Shaking the motion-sensitive controller while communicating with a female support character or fighting a female boss outside of her suit causes their breasts to bounce.
- Jiggle Physics is Japanese H-game maker Illusion's bread and butter. Depending on which game we're talking about, there may be sliders to adjust the amount of bounciness and the size of the breasts on the female character(s). Depending on the settings you choose, the results can range from subtle and surprisingly realistic to absolutely utterly ridiculous.