UE 5.8.2 Modular Rig Foot starching problem

[rasel2991]

A simple Base Mesh i have rigged using Auto Rig pro in blender and export via ARP (Auto Rig Pro)'s FBX export Window. After Importing In UE5.8 everything is working fine include Retargeting Fab Animations. Now After I add Control Rig in the sequencer the problem begins.

problem 1) Until i make Control Rig Layered only then i can tweak my animation. Otherwise it’s standing still.

problem 2) Both Foot starching and IK Pole hide inside the knee.

Please can anyone help me.

[ChenDong]

These two symptoms come from the same Control Rig setup, and both are normal with an Auto-Rig Pro skeleton until the rig is told how to read the animation.

Why it stands still unless the track is Layered. A Sequencer Control Rig track that is not layered replaces the whole pose. The clip underneath is thrown away and the rig outputs whatever its controls evaluate to. On a new rig those controls sit at their initial values, so you get the reference pose: standing still. Layered (additive) keeps the animation and only adds your offsets, which is why tweaking suddenly works. That mode is the right one if you only want to nudge an existing clip.

If you want a full Control Rig track instead of layered, the rig needs a Backwards Solve that runs before Forwards Solve and copies the current bones onto the controls: IK goals set from the foot bone locations, FK controls set from the bone rotations, pole placed in front of the knee. Without that, there is nothing to “match” the animation and the forward solve starts from the bind pose. For small tweaks, leave the Sequencer track on Layered and do not also key a full-body solve.

Why the feet stretch and the pole sits inside the knee.

• Stretch is on, and the goal is farther than the chain, or the chain length is wrong. ARP exports often come in with a root scale (100x from Blender meters, or a scale left on the armature). The skeleton looks fine for retargeted playback because that path uses the bones as imported, but Control Rig measures the chain in the rig and the goal in another space, so the leg extends. Apply scale in Blender, export at scale 1, and in the Limb / Basic IK node turn Stretch off until the goal sits on the foot.
• The item chain is too long. Use thigh and calf only. Leave out twist bones, the toe, and ARP’s extra IK/deform bones. Effector is the foot. A chain that includes a zero-length or twist bone solves short and then stretches to reach.
• The pole vector has no offset. If its parent is the knee or the calf and the local translation is zero, the pole is on the joint, the solver has no bend direction, and the control draws inside the knee while the leg flips. Parent the pole to the root, not to the leg, and place it along the knee’s forward axis, clearly in front of the joint, off the thigh-calf line. Do that in the rig’s initial pose, not as a Sequencer offset, or a layered track will keep adding to it.

Retargeted Fab clips playing correctly already tells you the skeleton can deform. The stretch starts when this Control Rig’s IK chain and pole do not match that skeleton. Fix the chain and the pole, disable stretch, and use Layered in Sequencer unless you have a Backwards Solve.