Rigging frog leg (multiple joints)


Could someone please help me with the rig of a frog leg? I know the basics of how to create a regular human leg IK rig. However, because the backlegs of my frog has multiple joints I cannot figure out how to make make a working rig.

I have tried the following:

  1. Copy the foot.L bone and call the new bone foot_IK.L and set the parent to the root bone (in the image the foot.L is parented to root, but it should be parented to backleg.L.003).
  2. Set the parent of foot_IK.L to the root bone.
  3. Add an IK-constraint to backleg.L.003 (stupid name, but I will fix this later, should be backleg.003.L)
  4. Finally added a copy rotation on foot.L with target foot_IK.L so that I also controls the foot with the IK-bone.

The problem is that this setup does not give me the possibility to control the leg as I would like. I have also tried setting a pole target to the right in the image and set this as pole target in the IK-constraint of backleg.L.003, but this does not give me the desired result.

The problem seems to be that there are two “knee”-joints. This is much similar to a bird leg I think.

I have tried finding good tutorials for this, but I cannot find anything useful. For example:
seems to be explaining what I would like, but the text is not complete and the full constraints are not explained.

Can someone give me some ideas on how to solve this?

To me that looks like a dog’s leg with different proportions. If this was a dog, backleg.L.003 would be a lot shorter, an extension of the foot, but at the end of the day, it’s still similar.

Use the forum tools at the top and do an advanced search for ‘pedro’ from the user ‘waylow’ in the ‘finished projects’ section. He created and rigged a dog named pedro that I animated with before and it worked very nicely. It used a 2 ik constraint setup with 2 pole targets, one for the knee, and one for your backleg.L.003 bone.

It has a python script for armature controls in the 3d view. This script may need to be updated.


Thank you!
I will try to reverse engineer that rig.