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Inverse Kinematics

This tutorial explains how to use Inverse Kinematics (IK) in PixelOver.
You will learn how to create a bone chain, attach images to it, set up an IK constraint, and control the chain using a target (and optionally a pole target).

Here a video example about how to make an IK setup animation in PixelOver:

What is Inverse Kinematics?

Inverse Kinematics (IK) lets you control a chain of bones by moving a target.
Instead of rotating each bone manually, the chain automatically solves rotations so the end of the chain follows the target.

IK is ideal for:

  • arms and legs
  • tails and ropes
  • tentacles
  • any rig that needs fast posing and animation

IK and Rest / Pose workflow

Inverse kinematics is only active in Pose mode.

  • In Pose mode, IK constraints are enabled and the chain will follow the target.
  • In Rest mode, IK constraints are disabled. This mode is used to setup the default placement of bones without any IK solving.

This makes it easier to build a clean rig in Rest mode, and animate it safely in Pose mode.

1. Create a bone chain (and attach images)

Create the bones

  1. Select the Bone tool
  2. Click in the view to create the first bone
  3. Click again to create the next bone as a child
  4. Repeat until you have a full chain

A typical chain looks like:

  • Upper arm → Forearm → Hand
    or
  • Thigh → Shin → Foot

Tip

Keep your chain simple. In most cases, 2 or 3 bones are enough for a limb.

Attach images to the chain

To animate pixel art characters, the usual workflow is to attach image parts to bones.

  1. Import your images (or split a character into parts using the Drawing workflow)
  2. In the scene tree, place each image under the bone that should drive it
    (using cut/paste or drag-and-drop parenting)

Example structure:

  • Bone_UpperArm
  • UpperArm_Image
  • Bone_Forearm
    • Forearm_Image
    • Bone_Hand
    • Hand_Image

Info

Parenting images to bones ensures the images follow the bone transforms automatically.

2. Add an IK constraint (on the first bone of the chain)

IK is applied to the root bone of the chain (the first bone).

  1. Select the first bone of your chain
  2. Check the properties panel
  3. Set the IK constraint under the constraint section

3. Create or pick an IK target

The IK target is the object the chain tries to reach.

Create a target

There are two common options:

  • Create a dedicated IK target object
  • Reuse an existing object as a target

Once created, assign it in the IK constraint as the Target.

Best practices for targets

For clean rigs, it is strongly recommended to:

  • Rename the target clearly
    Example: IK_Hand_Target, IK_Foot_Target
  • Set its length to 0px (so it behaves like a control point)

This makes the target easier to manage and prevents it from behaving like a visible bone segment.

Tip

Targets are meant to be controllers, not deformers. Keeping them at 0px makes them easier to position precisely.

4. Configure the angle constraint

Angle constraints force how the chain should bend.

This is useful to:

  • prevent unnatural bending
  • force a limb to bend in the correct direction
  • stabilize poses during animation

Positive vs negative angle constraints

Depending on your rig orientation, the chain may need to bend:

  • clockwise
  • counter-clockwise

This is why the constraint can be set to either a positive or negative angle range.

Example use cases:

  • An elbow should bend only one way (not backwards)
  • A knee should bend forward only

Tip

If the chain bends in the wrong direction, try switching the angle constraint sign (positive ↔ negative).

5. (Optional) Add a pole target for better control

A pole target helps control the plane of the IK chain, making the bend direction more stable and predictable.

Pole targets are especially useful for:

  • elbows and knees in 2D
  • 3D rigs, where the chain can twist unpredictably
  • setups where angle constraints are not available or not enough

Using a pole target

  1. Create a new target object (or reuse an existing one)
  2. Rename it clearly
    Example: IK_Elbow_Pole, IK_Knee_Pole
  3. Assign it as the Pole Target in the IK constraint
  4. Move the pole target to control how the chain bends

A simple rule:

  • The chain bends toward the pole target

Tip

Place the pole target slightly to the side of the limb (not on top of the IK target), so the solver has a clear bending direction.

Warning

In 2D, avoid using an angle constraint in the opposite direction as the pole target, as it may create unexpected behavior. If you use a pole target, it is usually better to set angle constraint to free, or ensure they do not conflict with the pole direction.

Summary

To set up IK in PixelOver:

  1. Create a bone chain
  2. Attach images to bones (parenting in the scene tree)
  3. Add an IK constraint on the first bone
  4. Create and assign a target (rename it and set length to 0px)
  5. Use angle constraints to control bend direction (positive or negative)
  6. Optionally add a pole target for more stable and precise control (especially in 3D)

To go further

Once IK is set up, you can:

  • animate targets using the Animation
  • combine IK with keyframes and imported animations
  • build full character rigs with multiple IK chains (arms + legs)