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There are tons of tools and instructions for making 3d models and animations in various software products. My question is: in video-game engines, when would you use a pre-rendered animation, and when would you use armature data in the model to manipulate your model in to the desired action?

Secondary questions: Are there any games that even use the model's rigging, in-game, or is everything pre-rendered?

Are there any human-readable file formats that contain armature data?

Lastly, from a OpenGL-level and up perspective, how would you implement a system for animating something like walking?

I am building an OpenGL graphics engine from scratch as a personal project, so if answers can cater to that context, it would be fantastic.

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  • \$\begingroup\$ That's a lot of questions. \$\endgroup\$ – Trevor Powell Apr 16 '15 at 3:08
  • \$\begingroup\$ I felt that they were all kinda relevant, and making a separate post for each would have been less efficient. \$\endgroup\$ – TaylorE Apr 16 '15 at 4:29
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Yeah, most games use a model's rigging and apply animation tracks to the bones in real time based on things happening in the game or player input. Animations can also be blended between to make new animations or transition from one animation to another. Animations can also be combined such that the lower half of a body is playing one animation and the upper half is playing a different animation. There is also something called parametric animation where a lot more of the animations are derived from a smaller set of animated bone data. There is also various levels of physics based animation such as ragdoll and inverse kinematics. I've specialized as an animation programmer at previous employers, check out this more detailed info based on my experiences and observations: http://blog.demofox.org/2012/09/21/anatomy-of-a-skeletal-animation-system-part-1/

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  • \$\begingroup\$ Cool! ill check it out. \$\endgroup\$ – TaylorE Apr 16 '15 at 4:30
  • \$\begingroup\$ I hope its informative! Skeletal animation is cool stuff \$\endgroup\$ – Alan Wolfe Apr 16 '15 at 4:31
  • \$\begingroup\$ So how does "lot more of the animations are derived from a smaller set of animated bone data" differ from current skeletal animation? \$\endgroup\$ – TaylorE Apr 16 '15 at 4:34
  • \$\begingroup\$ In the usual current type of animation systems, you have to have an animation handmade or motion captured for ever animation you can play on a model. Part of what parametric animation is all about is that it can interpolate and extrapolate entire animation sequences. So like, you give it a few walk animations with specific parameters associated with them (a walk straight forward, a walk up hill 20 degrees or a walk left 30 degrees) and it can use those to make a walk left 15 degrees or a walk up 40 degrees. \$\endgroup\$ – Alan Wolfe Apr 16 '15 at 4:37

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