Blender: weird pole bone behavior.

kanga

Hi
Blender 2.9
I am having trouble with inserting a pole bone on the elbow joint. Everything goes well till I make the chain length 1. The bone axis(es) have been unified to face +Y and transform history set to zero.  Am following a tute and studied that part quite a bit but haven't found a solution. Any help appreciated.

RN

In your image the Pole Target is empty. That Bone.040 is acting as the IK target -- where the bones in the IK chain, a single bone in this case, will try to reach. It's not acting as a Pole Target.

The IK constraint, when set to a Chain Length of 1, works the same as a Track To constraint: the single IK chain bone will just point to the target bone. Therefore the IK chain constraint is only useful for chain lengths of more than 1.

I don't know what guide you're following, but in my experience you make both the upper arm and the forearm bones part of the same IK chain. The IK target is then the wrist bone and the pole target is a flying bone near the elbow.

* This pole bone should be placed anywhere on the local +X axis of the base bone of the IK chain. This base bone will usually be the upper arm bone in a 2-bone IK chain that starts with upper arm bone and ends in the forearm bone.