Skinning
Binding a mesh to a skeleton
Also known as: Weight painting · Mesh binding
Definition
Skinning is the process of binding a mesh to a rig so that moving the skeleton deforms the mesh. Each vertex receives weights — fractional influences from one or more bones — controlling how it follows their motion. Quality skinning is invisible: a character bends, twists, and stretches naturally. Bad skinning produces collapsing joints, candy-wrapper twists, and shoulder pops.
In production
Modern engines support 4 (UE5) to 8 bone influences per vertex, and exceeding that cap during export silently truncates the lowest-weight influences, which can produce visible popping at the truncation point if not caught before shipping. Manual paint in Maya's Paint Skin Weights tool or Blender's Weight Paint mode produces hero-quality results; automated rigs like Mixamo handle background characters in seconds by projecting weights from bone proximity alone. The classic failure case is the "candy-wrapper" twist at the wrist or ankle, where a single joint rotation pinches the mesh into an hourglass shape — fixed either by adding a twist-bone that shares the rotation across two joints, or by using dual quaternion skinning instead of the default linear blend skinning, which handles twisting rotations far more gracefully at the cost of some volume preservation. Corrective blend shapes are often layered on top of skin weights to fix problem poses that weight painting alone can't solve.
