IK vs FK Rigs

Another Alec class today talking about the common faults in the walk cycles. Luckily none of these were mentioned in my own critic. These were;

  • In the contact pose; the heel roll on the back foot not being used, hips too high
  • In the down pose; the hips actually have to go down
  • The passing pose; the leg in contact is more likely to straighten and the foot roll should correct this
  • Overlapping follow through; swing the hand out a bit more to give the idea of drag, favor the inbetweens to the forward pose more for the shoulder and back for the hand/ elbow. An offset can also be created by moving the elbow/ hand keys forward a few frames each
  • The gimble lock causing arm problems; rectify on the unifeuler or by changing the rotation order.

He also advised us to play about with the IK/FK rig switch. I had mostly kept the FK when doing the walk cycle, however, Alec showed an easier way to do the spine, making it a more curved S shape- something I struggled to get for the jump.

I had a look into the actual meaning behind both of these phrases to understand when to use them.

So, IK stands for Inverse Kinematics. It uses node control rotation of the chain. In other words, if you move the hand, the rest of the arm follows. It is normally used when something has to be planted, for example, a hand against a wall while the rest of the body is animated.


Diagram courtesy of Digital Tutors. (Digital-Tutors Blog, 2013).

FK stands for forward kinematics, in which the joints rotate down a hierarchy. It provides more control than the IK but it means each joint must be moved independently. When animating this, you must start from the top of the arm down to the hand.


Diagram courtesy of Digital Tutors. (Digital-Tutors Blog, 2013).

I will definitely have a look at the IK for when fixing the body mechanic animation that I had blocked already.


Digital-Tutors Blog. (2013). Understanding Inverse and Forward Kinematics. [online] Available at: http://blog.digitaltutors.com/understanding-inverse-and-forward-kinematics/ [Accessed 18 Oct. 2016].


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