Problem with IK example in docs

Development Character & Animation
1

Hi!

I’m going through this example:

And I don’t understand two things about it:

https://docs.unrealengine.com/latest/images/Engine/Animation/IKSetups/Foot_IK_AnimBP_EventGraph.png

In this part, it only sets the X coord for the Effector Location. I thought it would use Z, since that’s up and down, and the goal is to move the guy’s feet up so they don’t go through something. Also, why after calculating the offset by tracing from the left and right foot does it multiply the right foot offset by -1?

2

I finally found it, after hunting around the demo for several hours.

The X axis of the bone in question points up on one foot, and down on the other. Hence using the X axis for changing the effector, and mutliplying the offset of one by -1.

left.png

right.png

3

Another odd thing about the demo. The docs show

https://docs.unrealengine.com/latest/images/Engine/Animation/IKSetups/IKTrace.jpg

The trace coming from the foot. It doesn’t. I drew red debug lines along the traces:

Untitled.png

It comes from the center of the pawn cylinder in Z, and through the foot bone in X, Y. Which makes sense when you think about it.