Why does my IK foot suddenly twist 180 when I face the other way?

The IK solver picks an ankle twist based on where the Pole Vector lands relative to the limb plane. If the Pole Vector flips sides during a turn, the chosen twist also flips, snapping the foot. Use a Pole Vector that orbits with the character, not a world-space target.

How should I drive the Pole Vector?

Make the Pole Vector a child of the character's pelvis (or local rotation reference). Now it rotates with the character and can't flip sides. For more control, drive it with a virtual bone offset by 30deg outward.

What's Two Bone IK with primary axis?

Two Bone IK in Control Rig has a Primary Axis input that constrains the limb plane orientation. Set to a predictable direction (forward of the character) so plane orientation doesn't suddenly flip.

Fix: Unreal Control Rig IK Foot Roll Flips on Direction Change

Quick answer: Parent the Pole Vector under the character’s pelvis so it rotates with the character. Set Two Bone IK’s Primary Axis to a fixed forward direction. Foot roll stops flipping when the character turns.

Character walks forward, IK feet plant correctly. Character turns 180. Each foot snaps to the wrong twist for one frame, then settles. The Pole Vector swept through the limb plane and the IK solver chose the other valid solution.

The Symptom

IK feet briefly twist 180 (or some other large angle) during direction changes. Or roll smoothly when the character moves but flip during sharp turns. Visible especially on sliding/strafing motion.

The Fix

Step 1: Pole Vector in character space. In Control Rig graph, the Two Bone IK’s Pole Vector control should be parented under the pelvis or a virtual bone that rotates with the character body. World-space pole vectors flip during character turns; character-space ones don’t.

Step 2: Primary Axis. Set the Primary Axis input on the IK node to the character’s forward (Y in UE conventions). This constrains the limb plane to remain forward-oriented.

Step 3: Smooth pole follow. If the pole is animated separately (foot IK rig), interpolate its position toward the target each frame instead of snapping. RemainingMs of 100–200 produces smooth following without lag-induced wobble.

Foot Roll Specifically

Foot roll comes from a separate control rotating the ball-of-foot bone around the heel. If your foot roll node uses a world-space axis, it flips. Use a local axis derived from the foot bone’s current orientation:

FootRoll Output Rotation:
  Axis = LocalUp(FootBone)
  Angle = RollAngleParameter

Verifying

Strafe-rotate the character through 360 degrees. Feet should plant correctly without flipping. Watch for snap; if any direction triggers it, the pole vector or primary axis is still world-space at that angle.

“Character-space pole. Local axis roll. Feet stay planted through turns.”

Related Issues

For Mecanim foot slide, see Mecanim foot. For AnimBP state machine, see AnimBP state machine.

Pole rides with character. Axis local. No flips.