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Just wondering that how many IK (Inverse Kinematic) bones should you apply to a game character before it starts to go resource hog. Basically should you try to get rid of IK bones and just try to animate without them but using IK bones makes things easier for the animator but might cause unnecessary use of resources and possibly cause bottleneck when calculating bone and mesh translations.

I'm using Blender and couple of animation tutorials are suggesting to use IK controllers and they indeed help a lot but when importing the character into a game they might be plain pointless since they are used only to help the animator.

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I'd expect that they are no costlier than a standard bone to most game engines. The way animations are normally exported is by storing the transform of each bone for every frame of animation (with some optimizations to save on storage space).

The standard skinned animation limitations in game engines tend to be:

  • A maximum of four bones influence each vertex. It'll pick the top four and ignore the rest.
  • The fewer bones the better as the model may need to be subdivided if there's too many due to limitations on older hardware. Aim to stay under about 64 bones where performance is more of an issue than animation quality.
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    \$\begingroup\$ Yep. You can animate it in Blender with as much IK stuff, constraints, etc. as you want, but the IK will be "baked out" when the animation is sampled for export to the game engine. Use of runtime IK would be much more restrictive, limited to e.g. placing a character's feet precisely on sloped ground. \$\endgroup\$ Commented Feb 10, 2013 at 22:52
  • \$\begingroup\$ @NathanReed Great to hear that IK bones will be baked out, didn't know that one at all. Thanks. \$\endgroup\$ Commented Feb 11, 2013 at 9:35
  • \$\begingroup\$ @EmJay Most 3D software doesn't bake out the IK automatically; usually you have to instruct it to do so, before exporting the animation data. \$\endgroup\$ Commented Feb 13, 2013 at 0:16

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