How to Adjust Bendy Bone Curves in Blender

Bendy Bones (B-Bones) in Blender allow riggers to create smooth, curved bone deformations without needing complex, multi-bone chains. Adjusting the curve of a Bendy Bone involves splitting the bone into multiple segments and fine-tuning its curvature using the Bendy Bones property panel, adjusting curve offsets, or assigning custom target handles in Edit or Pose Mode.

Step 1: Display Bones as Bendy Bones

Before adjusting curves, ensure your armature displays B-Bones visually:

  1. Select your armature.
  2. Go to the Object Data Properties tab (green armature icon).
  3. Expand the Viewport Display panel.
  4. Set the Display As option to B-Bone.

Step 2: Increase Bone Segments

A bone cannot curve if it only has one segment. To add flexibility:

  1. Select the bone in Edit Mode or Pose Mode.
  2. Go to the Bone Properties tab (green bone icon).
  3. Expand the Bendy Bones panel.
  4. Increase the Segments value (e.g., set to 5 or higher). Higher values produce smoother curves.

Step 3: Adjust Manual Curve Controls

Inside the Bendy Bones panel under Bone Properties, you can manually adjust the shape of the curve in Pose Mode using the following parameters:

  • Curve In / Curve Out:
    • X / Z: Adjusts the bending offset along the bone's local X and Z axes at the start (In) or end (Out) of the bone.
  • Roll In / Roll Out: Rotates the start or end of the bone segment along its local Y-axis to twist the curve.
  • Scale In / Scale Out: Adjusts the thickness/scale of the curve at the start or end of the segment.
  • Ease In / Ease Out: Controls the strength/tangency of the curve transition at the start and end points.

Step 4: Use Custom Handles for Dynamic Control

For intuitive animation control, you can link the curvature of a Bendy Bone to adjacent bones or custom control shapes:

  1. Select the Bendy Bone in Pose Mode or Edit Mode.
  2. Go to the Bone Properties tab and open the Bendy Bones panel.
  3. Locate the Start Handle and End Handle sections.
  4. Change the handle Type from Automatic to Absolute, Relative, or Tangent.
  5. Select a specific bone in the Custom picker field to act as the handle target.

When you move or rotate the assigned handle bones, the Bendy Bone will dynamically bend and adjust its curve to connect them seamlessly.