How to Preserve Volume in Blender Armature Modifier

Preserving volume during character animation in Blender prevents the mesh from collapsing or pinching at joints when bones rotate—an issue commonly known as the "candy-wrapper effect." This quick guide explains how to enable the "Preserve Volume" setting within the Armature Modifier, how the underlying Dual Quaternion skinning works, and best practices for achieving realistic deformations in your 3D models.

Enabling Preserve Volume in Blender

To fix collapsing joints on a rigged mesh, follow these steps:

  1. Select your 3D mesh object in the 3D Viewport.
  2. Open the Modifier Properties tab in the Properties Panel (represented by the blue wrench icon).
  3. Locate the Armature modifier applied to your mesh.
  4. Check the box labeled Preserve Volume.

Once enabled, Blender immediately recalculates how the mesh deforms around the underlying bones, maintaining the mesh's original thickness during extreme rotations.

Why Joints Collapse Without Preserve Volume

By default, Blender uses Linear Blend Skinning (LBS) to deform meshes. LBS calculates vertex positions by averaging the transformations of influencing bones linearly. While computationally lightweight, it causes the mesh to flatten or twist inward like a rolled wrapper when a bone undergoes sharp rotations, such as bending an elbow or twisting a wrist.

Checking Preserve Volume switches the deformation algorithm to Dual Quaternion Skinning (DQS). This mathematical approach preserves rotational scale and volume, keeping joints looking natural and full during poses.

Best Uses for Preserve Volume

Preserve Volume works best for organic models such as humanoids, animals, and creature meshes where muscles and flesh should retain bulk during motion.

  • Elbows and Knees: Keeps the joint rounded instead of flattening out when bent.
  • Wrists and Shoulders: Prevents the severe twisting collapse when rotating limbs along their axis.

Limitations and Artifacts

While Preserve Volume fixes many volume-loss issues, it has a few trade-offs to keep in mind:

  • Bulging at Extreme Angles: Dual Quaternion skinning can sometimes create unnatural bulging artifacts at extreme joint bends.
  • Shape Keys Interactivity: If you rely on corrective shape keys or drivers, Preserve Volume may alter how those shape keys deform the mesh. It is best to enable Preserve Volume before sculpting corrective shape keys.
  • Weight Painting: Preserve Volume is not a complete replacement for proper weight painting. Smooth and deliberate vertex weight blending across joints remains necessary for optimal results.