TwistSplit Lite - Free Bone & Weight Splitter

TwistSplit Lite cuts the active bone into 2 or 3 segments and splits its vertex-group weights between them, so the weights add up exactly as before.

Lite stops at 3 segments and 400 vertices. Full splits into up to 32 segments on any mesh, and Smooth falloff plus the twist rig lifts the wrist from 0.707 to 0.981 of its rest radius, in a 9 ms split ($8).
Remove Lite, install Full, done.

• Split: replaces the active bone with segments named <bone>.seg1 to .seg3, reattaches the children, and splits the vertex group on every mesh skinned to the armature.
• Add Demo: an arm with a skinned cylinder to try it on.
• Undo works, and each run reports how many weights moved.
• Limits: 2 to 3 segments, linear falloff, active bone only, skinned meshes up to 400 vertices in total (the demo size).

1. Install: Edit → Preferences → Get Extensions → Install from Disk, pick twistsplit_lite-0.1.0.zip.
2. N panel: in the 3D Viewport press N and open the TwistSplit tab.
3. Pick a bone: select the armature, make the bone active, set Segments (2 or 3).
4. Split: press Split.

• Split the forearm into 3 and weight-paint from there. Lite does not set up twist, so the wrist still collapses (see below).

On the demo run (arm with upper arm, forearm and hand bones, 1,148-vertex skinned tube), Blender 4.5 LTS, forearm split into 3 linear segments, hand twisted 90°:

• Vertex weight sums: unchanged (largest error 0.0).
• The split took 6 ms.
• Narrowest point of the tube at the wrist, as a fraction of the rest radius: 0.707, the same as with one forearm bone. Splitting alone does not stop the candy-wrapper collapse. The full version's twist setup does (0.981).

• Blender 4.2 or newer (extension format). Tested on Blender 4.5 LTS.
• Armature in Object or Pose mode with an active bone; skinned meshes are found through their Armature modifier.
• Up to 3 segments, linear falloff, active bone only. No twist preset, no mirror, no all-selected.

TwistSplit is $8 and adds:

• Twist Preset: Copy Rotation constraints set up for you. On the demo, the wrist went from 0.707 to 0.981 of its rest radius.
• Up to 32 segments, Smooth falloff.
• All Selected Bones and Mirror to Other Side.

Search TwistSplit on Blendkit.

Remove Lite before installing the full version.