Ragdoll engine

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Ragdoll in an animation from 1997

As ragdoll (also ragdoll engine , ragdoll physics , from English ragdoll : rag doll) are algorithms (in a game engine ) that simulate the movement behavior of injured or dying human bodies and generate corresponding animations . The movement is calculated in real time and is not pre-scripted. Such algorithms are part of the physics engine , which calculates the scene to be represented on the basis of a modeling according to physical laws, as is mainly used in action computer games.

history

Initially, the ragdoll algorithm was very unrealistic due to the still very weak CPU performance and was only limited to dead characters: when a character died, a predefined animation was played. The first attempts with this type of ragdoll engine were made in 1997 by various development studios.

As the computers got faster, the developers were able to implement physics simulations in real time that are now typical for today , with which the physics can be carried out on the respective bodies in real time. The appropriate skeleton is also modeled for the respective modeled figures, which can then be adapted to the circumstances (such as broken bones, dislocated shoulder, etc.) with the help of mathematical calculations.

The first game that had its own ragdoll engine was Jurassic Park: Trespasser , which was released in 1998 and made headlines because of the increased realism it created. However, the game was also criticized negatively because the embedding of the ragdoll engine had crept in many program errors . In addition, the virtual corpses give a sometimes very macabre impression, which is why such games are usually rated at least “ USK 16” due to German youth protection laws. Often the ragdoll behavior is therefore completely removed from the German versions in order to receive either a lower or even a release from the USK. One of the best-known examples of this is Far Cry , which was indicated in the first version (in which the Ragdoll could be reactivated relatively easily). However, most current games are affected by this practice.

Ragdoll Engine Limitations

The ragdoll procedures used in 2007 cannot, however, carry out the following operations, i.e.: With regard to these points, they do not (yet) fully correspond to reality:

  • Very small bones such as fingers or toes are not considered in most cases: they remain rigid. The developers are now trying to achieve useful results with the help of random techniques.
  • In certain cases of falling etc., some bones are not calculated completely realistically. The best example of this is the human knee and the calculation by Ragdoll: In the Ragdoll simulation, the knee is not bent to the right or left in the event of a fall, as it could in reality.

With the help of the Euphoria Engine , which was first used in GTA IV , these limitations were also overcome. The Euphoria Engine is also able to simulate a nervous system for each character in the game. Shots at certain parts of the body cause characteristic twitching. Natural reflexes are also taken into account.

Realism

Ragdoll engines sometimes simulate unrealistic behavior, which was (also) adopted from Hollywood films:

  • If you z. B. shoots an opponent in the chest in first person shooter games, this is sometimes pushed back several meters. The developers intentionally implement such unrealistic behavior with exaggerated effects in the game as it is supposed to look more dramatic and provide more action. The behavior is intended to simulate the impulse caused by the ball hitting it. In reality, such a phenomenon cannot be reconstructed even with powerful rifles: theoretically, based on the law of conservation of momentum, the shooter would have to fly the same distance against the direction of fire (if the shooter and the victim have the same mass). However, the prepared Sagittarius can also absorb the impulse through his body. Most of the weapons used in the games have mechanics that reduce recoil. Even a shotgun with about 2000  joules of muzzle energy fired 40 cm in front of a person does not move the body more than 6 cm from its original position. The result is exactly the same for a rifle that has a muzzle energy of 17,000 joules (roughly the energy required to move 1.7 tons up one meter).
  • With a grazing shot, the opponent sometimes moves very far in the same direction. In reality, this is not the case either.
  • In some games, the ragdoll algorithm simulates physical contortions, which are highly unlikely in reality.

Special engines for ragdoll simulation

  • Euphoria Engine : Also contains additional functions such as simulation of a nervous system
  • Havok
  • Maya (software) : The dynamic simulation plugin known as Bullet also includes a ragdoll option.

See also

Web links

Commons : Ragdoll physics  - collection of images, videos and audio files

Individual evidence

  1. ↑ Jesse Schell: The Art of Game Design: A Book of Lenses . Morgan Kaufmann, Burlington, Massachusetts 2008, ISBN 978-0-12-369496-6 , pp. 408-409 ( online view ).
  2. ^ Stevie Giovanni & Kang Kang Yin: LocoTest: Deploying and Evaluating Physics-Based Locomotion on Multiple Simulation Platforms . In: Jan Allbeck & Petros Faloutsos (eds.): Motion in Games: 4th International Conference, Mig 2011, Edinburgh, Kingdom, November 13-15, 2011, Proceedings . Springer, Heidelberg 2011, ISBN 978-3-642-25089-7 , pp. 228 ( online view ).
  3. ^ Richard Wyckoff: Postmortem: DreamWorks Interactive's Trespasser . In: Game Developer . UBM plc. May 14, 1999. Retrieved May 16, 2012.
  4. ↑ Article on Golem.de