SpringFX 8.2.4 — Documentation

Spring / jiggle bone physics for Blender by Auron3D.

1. Requirements

• Blender: 4.5 LTS – 5.2
• Operating system: Windows x64, macOS (Apple Silicon and Intel), Linux x64. The compiled solver is included for all three.
• Rig: any armature. Bone chains (hair, tails, ears, straps, soft clothing) give the best results.

2. Installation

1. Download the SpringFX zip for your purchase. Don't unzip it.
2. In Blender, open Edit → Preferences → Get Extensions.
3. Open the dropdown at the top right and choose Install from Disk…, then pick the zip. (You can also drag the zip onto the Blender window.)
4. Make sure SpringFX is enabled. The panels appear in the 3D Viewport sidebar (N) under the SpringFX tab.

Updating: install the new zip the same way; it replaces the previous version. Save your file first.

3. Quick start (1 minute)

1. Select the armature and enter Pose Mode.
2. Select the bones that should move (for example, all hair bones).
3. In the SpringFX panel press Add Physics. A new group is created with default springs.
4. Press play. Adjust Stiffness and Damping in the group settings until it feels right, or pick a Preset.
5. When you're happy, press Bake to turn the motion into keyframes — or export to VRChat PhysBones (section 8).

Repeat steps 2–3 for each part (hair, tail, ears…) so each gets its own group and settings.

4. Main panel and groups

• Add Physics — adds springs to the selected bones and puts them in a new group. A bone that already belongs to another group is moved to the new one.
• Clean Physics — removes the group selected in the list and fully clears the physics of its bones.
• Bake — bakes the simulation to keyframes (options in the Bake panel).
• Group list — one row per group. Double-click a name to rename it. The two icons toggle the location and rotation spring for every bone in the group.

Group settings (for the group selected in the list):

• Preset — ready-made settings for common cases.
• Drive Parameters — when on, the group's settings control all its bones. Leave it on unless you know you need per-bone values.
• Location Spring — bones lag behind and bounce in position: Stiffness, Damping, Speed, Gravity, Influence, Move Range, Max Distance.
• Rotation Spring — bones swing like a pendulum: Stiffness, Damping, Speed, Swing Range, Influence. This is what most hair and tails need.
• Reacts to Colliders — collision radius and how the group responds on contact (margin, stiffness, damping on impact, friction).
• Advanced — Chain Falloff (tips move more than roots), Lag / Delay, Smooth (removes high-frequency jitter), Air Drag, Wind Influence, Auto Bone-Size Tuning and Stiffness per Local Axis.

Rule of thumb: Stiffness decides how fast a bone returns to its pose; Damping decides how quickly the bouncing dies out. Change one at a time.

5. Collisions

• Bone colliders — select bones (for example head, neck, shoulders) and press Mark Selected as Colliders. Remove with Remove Collider Flag.
• Object colliders — in Object Mode, select an object and use the SpringFX — Object Collider panel to choose its shape: sphere, capsule (runs along local Y), plane (faces local +Z) or mesh.
• Use Blender Collision Objects — also collide with objects that have Blender's Collision physics enabled.
• Global response — Bounce, Friction and Iterations (more iterations resolve overlapping colliders more cleanly).
• Self Collision — turn on the master switch in the Collisions panel, then enable it on the groups that should keep apart.

6. Wind

Set the wind Direction, Strength, Turbulence (natural gusts) and Gust Speed. Each group decides how much it's affected with Wind Influence (Advanced).

7. Performance

• Precision — separate Viewport and Render / Bake precision. Bakes always use the Render / Bake setting.
• Substeps — 0 = automatic. Raise only for very fast motion.
• Update Every N Frames — lighter playback on heavy scenes; scrubbing and baking always simulate every frame.
• Skip Hidden Armatures / Skip Far Bones — don't spend time on what you can't see.
• Bake to Cache / Clear Cache — store the simulation so scrubbing is instant.
• Solver status — the panel shows whether the compiled solver is active. If it says pure-Python, SpringFX still works, only slower; reinstall the zip from your purchase.

8. Bake and export

• Bake Spring to Keyframes — writes the motion into the armature's current action. Keys on other bones are kept.
• Pre-Roll Warm-Up — simulates extra frames before the bake so springs settle. Use it for loops: one full loop length of Warm-Up Frames is usually enough.
• Apply Other Constraints — after baking, mutes the bones' other constraints, whose effect is already in the keys.
• Baked groups are removed after baking, because the motion now lives in the keyframes.
• Push Action to NLA — send the baked action to the NLA editor.
• Noise Modifier (Post-Bake) — adds noise to the selected bones' baked curves; apply, refresh or remove it at any time.
• Export to VRChat PhysBones — press Validate for PhysBones first to catch problems, then export. No bake is needed: the physics settings are exported, not keyframes.

9. Troubleshooting

• Bones don't move — check that the group has Location and/or Rotation enabled and that Drive Parameters is on. The panel warns when a group isn't driving its bones.
• Motion jumps at the start of a loop — enable Pre-Roll Warm-Up before baking.
• Jitter or vibration — raise Damping, add a little Smooth, or increase Render / Bake precision.
• Hair goes through the head — mark the head bone as a collider or add a sphere/capsule object collider, and increase the group's collision radius.
• Scrubbing is slow — use Bake to Cache.
• "Pure-Python solver" shown — reinstall the zip from your purchase; if it persists, contact support with your Blender version and OS.

10. What's new

• 8.2.4 — Blender 4.5 LTS support; compiled solver for macOS (Apple Silicon and Intel) and Linux; identical simulation across Windows, macOS and Linux; fixed baking on rigs that already have animation.
• 8.2.x — redesigned panel with renamable groups in a list, Add Physics / Clean Physics / Bake workflow, group fixes.

11. Support

Questions or problems? Use Contact the creator on this page. Include your Blender version, operating system and, if possible, a small .blend that shows the issue.