What is the difference between forward and inverse kinematics?

Updated October 2026 · How we answer

Forward Kinematics (FK)

In FK, you rotate each joint individually, and the position of the end effector (like a hand or foot) is determined by the combined rotations. This is how most skeletal animation works by default in Blender: you rotate a bone, and its children follow.

FK gives you direct control over each joint's rotation, which is great for creating natural arcs and overlapping action. However, placing a hand exactly on a doorknob or a foot on a stair can be tedious because you have to adjust multiple joints to hit the target.

• Simple to set up and understand
• No unexpected popping or flipping
• Good for broad, sweeping motions
• Requires manual adjustment for precise contact points

Inverse Kinematics (IK)

IK works backward: you specify a target location for the end of a chain (e.g., a hand or foot), and the software solves the rotations of the joints to reach it. In Blender, you add an IK constraint to a bone and set a target object or bone.

IK is ideal for keeping feet planted during a walk cycle or making a hand stay on a surface while the body moves. It can introduce issues like knee popping or unnatural twists, so limits and pole targets are often used to guide the solution.

• Easier to lock hands/feet to world positions
• Great for interactive posing and animation
• May require pole targets and joint limits
• Can be less predictable than FK

When to Use Each

Most animators use a mix: FK for arms and spine, IK for legs and sometimes hands. Blender allows you to switch between FK and IK on the fly using influence or by baking the animation.

For simple, stylized animations, FK alone may suffice. For realistic character interaction with the environment, IK is often necessary.

• Use FK for free-flowing motion and arcs
• Use IK for contact points and constraints
• Blender supports both on the same rig
• You can bake IK to FK for export