Understanding Bone Head and Tail in Blender

In Blender's armature system, every bone is a directional vector defined by two main control points: the head and the tail. The head acts as the bone's root and primary pivot point for rotation, while the tail defines the bone's end, length, direction, and twist orientation. Understanding the distinction between these two elements is essential for building proper character rigs, setting up bone hierarchies, and animating smoothly.

The Bone Head (Root)

The head, also referred to as the root or origin, is the starting point of a bone. By default, in an octahedron bone display, it is the thicker end of the shape.

  • Pivot Point: In Pose Mode, bones rotate and scale around their head. It serves as the joint anchor for motion.
  • Parenting Target: When you parent one bone to another, the child bone connects directly to the parent's head or tail, establishing the skeletal chain.
  • Coordinate System: The local origin \((0,0,0)\) of the bone is located precisely at the center of the head.

The Bone Tail (Tip)

The tail, also known as the tip, is the end point of the bone. It is represented by the narrow, pointed end of the default octahedron bone.

  • Direction and Vector: The position of the tail relative to the head determines the bone's direction and local Y-axis alignment.
  • Bone Roll: The alignment between the head and tail helps define the bone's "Roll" value, which controls how the bone twists around its own length.
  • Kinematics Target: In Inverse Kinematics (IK) and tracking constraints, the tail is frequently used as a target or snapping point for other elements in the rig.

Working with Heads and Tails in Different Modes

  • Edit Mode: You can select and translate the head and tail independently to change the bone's size, angle, and position. Moving either point alters the rest pose of the armature. Selecting the body between them moves both the head and tail together.
  • Pose Mode: Individual heads and tails cannot be moved independently to deform the bone length (unless stretch constraints or bone scaling are applied). Instead, the entire bone transforms as a single unit, pivoting around the head.