IK Constraint

4m 46sPublished Sep 18, 2023

SummaryVersion Notes (Draft)

The IK (Inverse Kinematics) Constraint allows you to control a chain of bones using a single point, rather than rotating each bone individually (Forward Kinematics). This is particularly useful for animating limbs like arms or legs, where moving a hand or foot automatically calculates the necessary joint rotations.

FK vs. IK: Forward Kinematics (FK) is default; IK is superior for limbs that need to stay planted or follow a specific endpoint.
Visual Feedback: Bones under the influence of an IK constraint appear highlighted in yellow in the viewport.
Hybrid Rigging: You can animate the "Strength" property down to 0% to temporarily disable IK and return to manual bone rotation (FK) for specific frames.

📌 Key Points

Inverse Kinematics: control bone chain rotation by moving a target point.

📝 Notes

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Step by Step

01:11

Creating a Target

Create an empty group (G) and change its type in the Inspector from "Group" to "Target" to serve as the control point.
01:52

Applying the Constraint

Select the last bone in your chain, go to the Inspector, and add an IK Constraint.
02:03

Linking the Target

In the constraint settings, use the target selector to pick the Target group you created in step 1.
02:50

Setting Bone Count

Adjust the "Bone Count" property to determine how many bones up the chain are influenced by this specific IK target (e.g., set to 2 for a knee/elbow joint).
03:32

Inverting Direction

Use the "Invert Direction" toggle if the joints are bending the wrong way (e.g., an elbow bending backwards).
03:52

Animating IK Properties

In Animate Mode, you can key both the "Invert Direction" and "Strength" properties to switch between poses or blend IK with Forward Kinematics.