I'm confused with this, when I have the arm in my desired position (the rest position A1) the upper arm doesn't bend to meet the IK target bone, see A2.

But with the lower arm rotated in B1, when I move the IK target upwards, the arm bends to meet it, see B2.

pictures of problem

Why is that? What can I do to fix?

  • $\begingroup$ It will be nice to upload the .blend file here if convenient. $\endgroup$ – Leon Cheung Nov 25 '14 at 7:39
  • $\begingroup$ Here's the .blend file: link $\endgroup$ – DSMK2 Nov 25 '14 at 11:50

According to your file, IK limits are defined. You need to unlock related axis, or set appropriate angle ranges for consistency, in order to avoid control conflicts.

enter image description here

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  • $\begingroup$ Control conflicts? Though, if I want to limit joint rotation to just an axis along with a limited range of rotation, use the limit rotation constraint instead? $\endgroup$ – DSMK2 Nov 25 '14 at 14:53
  • $\begingroup$ Maybe I don't fully follow you. In your case, you limite the X rotation from -90 to 0, which means the IK control style, as you expected in your question, cannot work out of this range, by all means. You my try to toggle off the Limit for X axis as shown in my screenshot, then give it a try. $\endgroup$ – Leon Cheung Nov 25 '14 at 15:10
  • $\begingroup$ I've took off the limit for the x axis, making the arm rotate freely to meet the IK target. But I want the arm to only be able to rotate 90 degrees, not freely. $\endgroup$ – DSMK2 Nov 26 '14 at 0:42
  • $\begingroup$ Starting to think that I really can't get around this without having the armature "bent" in the first place. And using rotation constraints won't work because the IK constraint will override it. Thanks though! $\endgroup$ – DSMK2 Nov 26 '14 at 1:44
  • $\begingroup$ In that case, I think you need to limit IK rotation for the parent bone. $\endgroup$ – Leon Cheung Nov 26 '14 at 4:43

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