IK Setup Editor

An IK Setup adjusts a 3D skeleton toward a target after its animation pose is evaluated. You can use it to point a head at an Object or place a hand near a handle.

Prerequisites

Use a 3D project and show Advanced resources. Import a Model with a skeleton, then open an IK Setup and choose that Model in Preview Model. A static mesh has no bones for the constraint picker.

Create and Preview a Constraint

1. Add a constraint and give it a distinct name.
2. Choose its type. Two-Bone Reach is for arms or legs; Look at is for a head, eyes, or turret; Chain is for a tail or spine; Ground Legs adjusts feet against the surface.
3. Choose bones from the preview Model. For a two-bone constraint, use a connected root, middle, and end. For Look at, choose the bone and its facing axis.
4. Set the constraint’s weight and target controls. Start with a nearby target so you can distinguish a broken mapping from an unreachable point.
5. Play an imported clip in preview and move the test target. Save and reopen the resource, then select it in the Model Editor’s IK Setup field.

Bone selectors describe the preview Model. Assignment to a different skeleton requires matching names and hierarchy. Recheck constraints after reimporting a Model whose skeleton changed.

Tune the Solver

Two-bone bend controls decide which way the elbow or knee turns. Softness reduces abrupt extension near the reach limit. Weight mixes the correction with the existing pose; zero leaves that pose, while a larger weight applies more correction.

Ground Legs needs Foot Bone and either an explicit Leg Root or an automatic joint count. Body Bone and Body Follows can adjust the pelvis. Lock Feet in Place has speed, lift, and stretch thresholds in its tuning controls. Ground constraints adjust a pose or animation; they do not generate a walking gait.

Longer chains use iterative solving. Increase iterations only when the chain needs them, and check the result at the intended target distance. More iterations cannot make a target reachable beyond the chain’s length.

Check the Game

For a head-tracking check, create a Look at constraint named headLook on the imported Model’s head bone. Select its Forward Axis in preview and set weight to 1. Choose the saved IK Setup in the Model Editor’s IK Setup field.

Place one Object named Character using that Model and one visible Object named Look Target near its face. Create a Logic Component named Track Head, set its dimension to 3D in Details, and attach it once to Character.

In When Created, connect Set IK Target, then Animate IK Weight, then End. Both Actions are under 3D World > 3D Inverse Kinematics.

Action	Field	Value
Set IK Target	Applies To	SELF
Set IK Target	IK Constraint	headLook
Set IK Target	Target	object
Set IK Target	Object	Look Target
Set IK Target	Z (Height)	0, for no height offset above the target’s origin
Animate IK Weight	Applies To	SELF
Animate IK Weight	IK Constraint	headLook
Animate IK Weight	Weight	1
Animate IK Weight	Seconds	0.2

Start a fresh Debug Play. The head should turn toward Look Target while the animation continues. Move Look Target with its own Logic and check that the head follows. With several placements of Look Target, object mode selects the nearest live instance and resolves it again each frame.

To release the constraint, add a discrete Command or Custom Event on Character. Run Animate IK Weight with headLook, Weight 0, and Seconds 0.2. Follow it with Wait for 0.2 seconds, then Set IK Target with headLook and Target off. The weight Action starts the fade and continues immediately; Wait lets the fade finish before removing its target. Compare the returned pose with the original animation. Starting the fade every Step can keep resetting it.

Set IK Target chooses the target request; Animate IK Weight changes its strength. See Set IK Target and Animate IK Weight for their fields.

For Target point, choose Position Relative To World and enter X, Y, and Z (Height) in metres. X and Y describe the ground plane; Z is height. Target camera uses the runtime 3D Camera. In object mode, Z (Height) is an offset above the followed Object. Ground Legs targets the surface automatically and ignores Set IK Target requests.

Expected result: the chosen bones respond while the rest of the animation continues. The Model’s world Transform and scale must be included in the check; an editor-space target and a world-space target are different positions.

Troubleshooting

If nothing moves, check skeleton presence, bone names, constraint assignment, enabled state, and weight. If the limb bends backward, adjust its bend direction or pole angle. If a head looks sideways, inspect Forward Axis. If feet drift, check the underlying animation, surface, lock thresholds, and target reach before increasing solver strength.

If the Actions are absent, set the Logic dimension to 3D. If preview works but play does not, compare the exact constraint name and the Model’s IK Setup assignment. Check target reach and scale before increasing weight or solver iterations.

See Models and Animators for source import and pose playback.