Snapping issue in Simple IK rig.
I'm trying to animate with with simple IK rig.
I'm in IK, positioning the arm. And the arm looks twisted like this.
https://prnt.sc/z8_2MGVxyVd3
I snap to FK.
I pose the arm in the correct/natural way.
But if I'm back to work with IK, it turns back to the wrong pose again.
What to do?
And let’s say, I don’t care about the IK, as long in FK it looks good. When I baked, will it use the keyframe I made in FK, or will it use the IK and overide the FK bones keyframe?
Comments (9)
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- changed status to open
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repo owner For some reason the forearm twist bone copied the rotation of the forearm ik bone rather than the hand ik bone. Fixed now.
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repo owner No, that doesn’t work, and it was never implemented. The problem is that the forearm moves around strangely for intermediate values of the ik influence. A local copy rotation constraint is not perfect, but it behaves in a much more stable fashion.
The mhx rig avoids this issue by adding an extra bone. The hand is child of hand0, which shares location with hand and is parallel to the forearm.
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Usually the ik influence is a toggle, that is, either one or zero, it doesn’t have intermediate values. The keyframes for snapping in ik influence should be set as constant interpolation mode, not linear. Linear doesn’t work for snapping. That said, again I don’t use the addon rigs so if you like that design I’ll close as resolved. Let us know.
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repo owner We use influence rather than the mute property for the ik constraints, to make a smooth transition between fk and ik. Then it is bad if intermediate values are off. Although I mainly do stills myself and interpolation is not a problem in that case.
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Mute doesn’t work for animation, influence is right you do have to use it for animation. For snapping you should use constant interpolation because otherwise it doesn’t snap, that is, if there’s intermediate values then it doesn’t snap by definition. I don’t see why “it is bad if intermediate values are off“.
But again if you like it this way we can close as resolved. Let us know.
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- changed status to resolved
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1.7.4.2029
It seems Thomas changed the setup, I don’t know if this is on purpose but this way it doesn’t work. The forearm setup should be as explained in
#1708in point 2 forearm twist, with copy rotation and dumped track on the ik hand, that way the forearm twists automatically when we pose the hand. I do my own rigs and I don’t use the addon rigs myself, though I contributed to them a little, so I don’t check when Thomas changes things.We have to wait for Thomas to reply when he’s back.