What Are Bendy Bones in Blender?

Bendy Bones (also known as B-Bones) in Blender are a rigging feature that allows a single bone to act like a flexible, curved spline rather than a rigid, straight line. By subdividing a bone into multiple internal segments, animators can create smooth, organic deformations for curved objects without building complex, multi-bone chains. This article covers what Bendy Bones are, why they are useful, and how to configure them in your Blender projects.

Understanding How Bendy Bones Work

In a standard armature, a bone is a rigid structure that bends only at its joints. Bendy Bones alter this behavior by breaking the space between the root (head) and tip (tail) into multiple curved segments.

Although a Bendy Bone displays and deforms mesh like a flexible chain of small bones, it is still selected, transformed, and keyframed as a single bone in Pose Mode. The curve of the bone is calculated mathematically using Bézier interpolation, giving the mesh a smooth, continuous bend.

Key Advantages of Bendy Bones

  • Simplified Rigs: Instead of using 5 to 10 individual bones to rig a flexible object, you can use a single Bendy Bone, drastically reducing clutter in the viewport and Outliner.
  • Better Weight Painting: Deforming a mesh with one flexible bone is often cleaner than painting weights across many small, individual bones.
  • Stylized Animation: They are ideal for "squash and stretch" cartoon animations, allowing limbs, spines, and facial features to bend fluidly.

Essential Bendy Bone Settings

To use Bendy Bones, you must first set the Armature display type to B-Bone under the Armature Data Properties tab. You can then adjust the primary parameters found in the Bone Properties panel under the Bendy Bones section:

1. Segments

This controls how many subdivisions the bone has internally. Increasing the segment count (e.g., to 8 or 16) produces a smoother curve. A value of 1 behaves like a standard rigid bone.

2. Handles

Handles determine how the start and end of the bone curve. By default, the curve aligns automatically with adjacent connected bones. However, you can change the In and Out handle types to Absolute or Relative and assign custom target bones to control the curve tangents manually.

3. Ease In and Ease Out

These settings control the strength or "stiffness" of the curve at the head (Ease In) and tail (Ease Out) of the bone. Higher values make the bend transition more gradually, while negative values invert the curve direction.

4. Scale and Roll

Bendy Bones allow you to adjust the scale and roll along the length of the bone. You can manipulate the Start and End values for X/Y scale to achieve dynamic taper or squash-and-stretch effects automatically along the curve.

Common Use Cases

  • Tails and Tentacles: Effortlessly animate whipping or waving motions with minimal keyframes.
  • Spines and Necks: Create realistic, curved spinal movements for characters.
  • Stylized Limbs: Achieve classic rubber-hose style arms and legs that bend without sharp elbow or knee joints.
  • Facial Rigging: Form smooth, curved controls for eyebrows, lips, and eyelids.