The Limit Property is not working as expected

posted to: IK Constraint Demo

Hi,

I've set limits for the Thigh bone which is a bone in the IK Chain.


I now selected the Foot bone (a Target bone in the IK Constraint) and moved it and noticed that the Thigh bone is going way past its limits. 


I was wondering if you know why it's happening.

  • chrislim replied

    Hey there,

    I'm still a beginner at all this, but I did some digging around and it seems that when you use a pole target, the limit rotations of the bones in the IK chain are ignored.

    In this demonstration, since we are using a knee pole, it ignores the limit rotations in favor of always pointing the thigh in the direction of the pole angle. If you clear the pole target in the IK constraint, the limit rotations start working as expected.

    I'm still really new to rigging, so more experienced users are more than welcome to chime in.

    2 loves
  • chrislim replied

    One possible workaround to this might be to clear the knee pole from the IK constraint, then instead use a locked track bone constraint on both the thigh and shin (both targeted to the knee pole.)

    This way you still get a "pole-like" behavior from the locked track constraints, while the limit rotation properties are respected in the IK tab.

    I tried this and the "pole" (target of the locked track constraints) seems to work just like a regular pole. However, once you reach the rotation limits you set, the behavior of the "pole" starts to break down in favor of the rotation limits.

    2 loves
  • deepakj replied

    Thank you for the pointers cchrislim.

    1 love
  • Wayne Dixon replied

    Hi Deepak,
    Yes ChrisLim is correct.  Forgive me if I failed to mention that in the course.

    But I do like his solution there, nice on cchrislim

    In my view, you would only use the limits on the IK when rigging something mechanical.  If you added it on something organic (like an arm) you would likely run into a limitation where the animator needed to move it in a direction that is 'limited'.  And it would likely pop or flip when one side of the 'limit' to the other.

    Hope that makes sense.