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I'm trying to animate in-between keyframes for skeletal animation but having some issues. Each joint is represented by a quaternion and there is no translation component. When I try to slerp between the orientations at the two key frames, I got a very wacky animation. I know my skinning equation is right because the animation is perfectly fine when the animation is directly on a keyframe rather than in-between two.

I'm using glm's built in mix function to do the slerp, so I don't think there are any problems with the actual slerp implementation.

There's really one thing left that could be wrong here. I must not be in the correct space to do slerp. Right now the orientations are in joint local space. Do I have to be in world space? In some other space along the way? I have the bind pose matrix and world-space transformation matrix at my disposal if those are needed.

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A code snippet may help, possibly with hard numbers showing the quaternion values at two keyframes and the value of the interpolation between the two. – Byte56 Apr 17 '12 at 21:22

Stumbled upon this post:

Interpolation doesn't work too well when the dot product of the two quaternions is less than 0. If this is the case, I just negate one of them and then do the slerp.

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Note: this should be done by you, when you prepare your animation data. All quaternions stored in your animation should have a positive W component; that way, the interpolation will always go the "right" way (ie: the short path). – Nicol Bolas Apr 17 '12 at 23:00

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