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Ragdoll Physics (Video Game Deaths)



Yet another video game physics blog:

As video games become more and more advanced, naturally, their physics improve as well. Advancements in computing technology allow for more realistic movements in player models - and this leads us into a discussion in something known in the computer physics world as "ragdoll physics".

Anyone who has played a video game involving the death of a character (which is, well, most of them) knows that death animations are anything but static. This is to make them appear more human, by simulating human joint/muscle/bone movements during a fall or collapse of some sort.


(A real-life example of "ragdoll physics" - ouch.)

In the beginning, when video games lacked the processing power to compute accurate "death sequences", manually created animations were used. Basically, the animations would come from one of several sequences of pre-drawn frames. By today's standards, it's primitive, but it was a clever solution.

As computing power increased, though, it was possible to simulate real-time physical simulations. Video games could now include these ragdoll simulations by constraining rigid bodies such that their bones and joints react realistically to their circumstances. These constraints usually cause a lack of muscle stiffness at the moment of death or collapse, so that the model can collapse authentically, hence the term "ragdoll". This can lead to some interesting (and often humorous) results.


(From the ever-popular Grand Theft Auto - this franchise is well-known for its ragdoll physics.)

Finally, some examples of different ragdoll physics:

Inverse kinematics: This involved using a preset animation, but by using kinematics to provide a physical constraint, the character was forced into a possible position after death. Used in the first Halo game.

"Blended" technique: Provided realistic effects by using a preset animation, where the animation was constrained to what that physical system would allow. Used in Halo 2 and 3, Call of Duty 4, Left 4 Dead, and Uncharted.

Video game physics have come a long way. Jurassic Park: Trespasser, while a faulty and buggy game, was a pioneer in the use of ragdoll physics. Just looking at these huge advancements within the course of a couple decades, we can assume that character models in video games will continue to become more and more humanlike.


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