Shoot a guard in an older 3D game and he plays his death animation: the same stagger and slump every time, whether he was standing on a staircase or against a wall. A ragdoll replaces that stored animation with a body. The character becomes rigid limbs joined at constrained joints, and the moment it dies the physics engine takes over, so it falls the way the forces dictate: back down the stairs, over the railing, folded against the wall. The word appears in Edge in 1998 as a simile for what such a body does when dropped. By 2002 reviewers used it as a feature name without explanation, and by 2005 the physics vendors were trying to get past it.
Fast facts
- The idea in print: Chris Hecker in Edge, August 1998: build a creature from “bodies and joints” and “you can drop this creature and it will buckle and fall to the ground like a ragdoll”.
- Early shipping use: IO Interactive’s Hitman: Codename 47 (2000), whose corpses fell “in unique ways depending on where they were hit”.
- The showcase: MathEngine’s Karma engine in Unreal Tournament 2003, which Edge called “the first attempt” at ragdoll characters and which PC Gamer said showed off ragdoll deaths “to gratuitous effect”.
- The middleware answer: Havok 2.0 (2003), “up to ten ragdoll models in realtime”.
- The put-down: Gabe Newell’s “flopping-around corpses”.
The word
Edge’s August 1998 feature on character animation gave most of a page to Chris Hecker, “a veteran coder and respected authority on ingame physics”, and his argument against motion capture: it “doesn’t tell you anything about the dynamics of the movement. What does a motion-captured animation do if one of its limbs hits something or gets tied down? Nothing. It either continues the animation and looks stupid, or it stops playing the animation and looks stupid!”
His alternative was the constrained body. Take a lower arm, “constrain it to another body (the upper arm) and set the type of joint between them… a hinge or elbow”, switch on the simulator, and “if I pull on the wrist, the arm straightens out and then drags along after me. Basically, it acts like a real arm.” Build a whole creature that way and, if the simulator handles contact, “you can drop this creature and it will buckle and fall to the ground like a ragdoll.” That sentence describes the whole technique. Hecker was clear that the falling-down part was the easy bit: “the real hard part” was “a controller that acts as the creature’s muscles and makes it stand up and act like it’s alive”. Games would ship the easy bit first.
First bodies
DreamWorks Interactive’s Trespasser: Jurassic Park (1998) had already attempted physics-driven living creatures, with skeletal dinosaurs and simulated muscles. That was a different ambition from making a dead body fall; the physics engines entry follows its development and reception.
The corpses came two years later, in Hitman: Codename 47 (2000). Thomas Jakobsen, who wrote its physics at IO Interactive, described the system in “Advanced Character Physics”, presented at the Game Developers Conference in 2001. It moved cloth and plants, and made “dead human bodies fall in unique ways depending on where they were hit, fully interacting with the environment”. A Hitman corpse was a stick figure: points joined by fixed-length “sticks”, with angular limits for the joints and extra constraints between the knees so that “the legs never cross”. Each stick collided with the scenery as a capped cylinder, and the limbs the player saw were fitted to the points afterwards, “making certain that knees and elbows bend naturally”. The method was cheap because it did not solve the constraints exactly: it nudged each one back into place in turn and let the result settle over a few frames. Jakobsen noted that the press had called the result “lifelike death animations”, which he thought an oxymoron.
Flopping-around corpses
Looking back from 2005, Edge credited “the first attempt” at physics-driven characters to “the integration of MathEngine’s Karma engine into Unreal Tournament 2003 to drive the motion of ragdoll characters”. Hitman had shipped physics-driven bodies two years earlier, so Edge’s “first” is best read as the first time a game sold itself on ragdolls. PC Gamer’s 2002 review found the feature already “much-touted”: Bombing Run’s “spiky girder-filled pits” were “a device that shows off the Math Engine ragdoll physics to gratuitous effect”, and dying meant “a realistic and ghastly sequence” of a body tumbling. It “only modelled the impact of forces and collisions on inanimate skeletons”, in Edge’s words, and that is what Valve’s Gabe Newell would later call “flopping-around corpses”.
The demand was there regardless. Havok’s Steve Collins told Edge in March 2003 that “70 per cent of top ten games are about characters” and that “gamers aren’t happy seeing characters sliding along with their shoulder or arm embedded in the wall anymore”. Havok 2.0 was re-engineered so it could “run the dynamics of up to ten ragdolls” where its predecessor “struggled with just one at a time”, and Remedy was using it for “collision detection and character controllers” in the Max Payne sequel.
In games
Max Payne 2 arrived at the end of 2003 with ragdolls that “may not match the flying limbs and broken faces of Soldier of Fortune”, but whose “throwaway approach to life and death is genuinely shocking”. A year later two games in the same issue of Edge showed where the technique was going. Half-Life 2 was praised as “a game in which physics are more than just an excuse for ragdoll deaths”: the gravity gun that could “drag objects, pick them up and carry them about” was “the core tool”, and the corpses were incidental. FlatOut, “a racing game with physics as a weapon”, went the other way and made the ragdoll the entertainment: bonus events that “involve ejecting your drivers through the windscreen at the optimal moment (and angle) to get them to fly as far or as high as possible. Watching them twist and flop through the air is as hilarious a pleasure as it is a guilty one.”
Beyond the ragdoll
By the Game Developers Conference of 2005 the vendors were describing the ragdoll as a starting point. James Golding, “a one-time MathEngine employee who moved to Epic to help with the initial Karma work” and now worked on physically based animation in the Unreal engine, wanted to “‘direct’ your scene instead of meticulously controlling the movement of every bone”: “Our crates now move as good as they look - it’s time to start doing the same for our creatures.” Havok’s Collins put the target more simply (“We’ve all seen ragdolls being blown up and expect them to be able to get up again”), and the company’s newest product was Havok Animation, “physics-based simulation for believable in-game character motion”. Seven years after Hecker’s interview, the industry was working on his “real hard part”.
Sources
- Edge issue 61, August 1998: character animation feature (Chris Hecker on motion capture, constrained bodies and the ragdoll simile).
- Johnny L. Wilson, Trespasser: Jurassic Park preview, Computer Gaming World issue 152, March 1997: Seamus Blackley’s skeletal dinosaurs with “artificial muscle connections”. Computer Gaming World issue 176, March 1999, review index: the game’s review in the January 1999 issue.
- Thomas Jakobsen, “Advanced Character Physics”, IO Interactive, presented at the Game Developers Conference, March 2001 (web): the physics of Hitman: Codename 47, the stick-figure corpses, their constraints and collisions. https://www.cs.cmu.edu/afs/cs/academic/class/15462-s13/www/lec_slides/Jakobsen.pdf
- Unreal Tournament 2003 review, PC Gamer (UK) issue 115, November 2002: Bombing Run and the “much-touted ragdoll physics”.
- “The next step for physics”, Edge issue 121, March 2003: Havok 2.0 and Steve Collins; Remedy’s Markus Stein on the Max Payne sequel.
- Max Payne 2 review, Edge issue 132, January 2004, p. 104.
- Half-Life 2 review, Edge issue 143, December 2004, p. 102; FlatOut review in the same issue.
- “Beyond the valley of the ragdolls”, Edge issue 149, May 2005, pp. 66–70, with the sidebar “Getting into character”: Unreal Tournament 2003 as “the first attempt”, Newell’s “flopping-around corpses”, James Golding and Havok Animation.