Jaw Bone Lip Sync

Overview

The Jaw Bone Target (CrystalLipSyncJawBoneTarget) component is a lightweight alternative to the standard CrystalLipSyncBlendshapeTarget. Instead of driving SkinnedMeshRenderer blendshapes, it rotates a jaw bone to open and close the mouth.

This is ideal for characters that have no blendshapes at all ... the jaw simply opens wider for loud vowels and closes during silence, giving a convincing "talking" appearance at minimal cost.

The Jaw Bone Target reads from the same CrystalLipSyncController as the Blendshape Target. All audio analysis, viseme classification, and smoothing features work identically ... only the output method differs.

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When to use it

Scenario	Use Jaw Bone Target?
Low-poly characters (mobile, retro, voxel)	Yes ... no blendshapes needed
Stylised / comic characters with simple geometry	Yes ... one rotating bone is enough
Procedurally generated characters with a rigged jaw	Yes ... assign the bone at runtime
VR hands / avatars with a jaw bone but no face mesh	Yes
Robots / puppets with a hinged jaw	Yes ... perfect mechanical open/close
Realistic characters with full face blendshapes	No ... use CrystalLipSyncBlendshapeTarget instead
Characters with ARKit / FACS blendshapes	No ... blendshape mapping gives far better results
Characters needing distinct vowel/consonant shapes	No ... jaw-only cannot distinguish lip rounding, bilabial closure, etc.

Jaw Bone lip sync produces open/close only. It cannot distinguish between different mouth shapes (e.g., "AH" vs "OO" vs "EE" all produce the same jaw-open). For characters where the camera is close to the face, blendshape lip sync will always look significantly better.

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Setup

Option A ... Setup Wizard (recommended)

1. Open Tools → Crystal LipSync → Setup Wizard

2. Drag your character into the Character GameObject field

3. If no viseme blendshapes are found, the wizard automatically suggests Jaw Bone mode

4. You can also manually switch the Lip Sync Target dropdown to JawBone

5. Click Setup Character

The wizard will:

• Add an AudioSource and CrystalLipSyncController (as usual)

• Add a CrystalLipSyncJawBoneTarget instead of a BlendshapeTarget

• Auto-detect the jaw bone in the hierarchy

Option B ... Manual setup

1. Ensure your character has a CrystalLipSyncController with an AudioSource assigned

2. Add the CrystalLipSyncJawBoneTarget component (Add Component → CrystalLipSync → Jaw Bone Target)

3. Assign the Controller reference

4. Assign the Jaw Bone transform (or click Auto-Detect Jaw Bone)

5. Adjust the Axis, Max Angle, and Invert Direction to match your rig

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Settings

Setting	Default	Description
Controller	...	The CrystalLipSyncController that provides viseme weights and volume data.
Jaw Bone	...	The Transform to rotate. Typically the first child of the head bone (named Jaw, Chin, Mandible, etc.).
Axis	X	Which local axis the jaw rotates on. Most humanoid rigs use X or Z.
Max Angle	15°	Maximum rotation when the jaw is fully open. Typical range: 10°...25°.
Invert Direction	false	Flip the rotation direction if the jaw opens the wrong way.
Drive Mode	Viseme	What drives the jaw opening ... see below.
Smoothing Speed	20	How quickly the jaw responds to changes. Higher = snappier.
Intensity	1.0	Global multiplier for jaw opening (0...1).
Volume Multiplier	40	Scales raw audio RMS (which is very small) up to a usable range. Only used in Volume or Combined mode.

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Drive Modes

Mode	Source	Quality	Use case
Viseme	AA (open vowel) viseme weight	Best	Default ... uses the full FFT analysis pipeline to detect open-mouth sounds
Volume	Raw audio RMS amplitude	Basic	Simplest open/close; every sound opens the jaw proportionally to loudness
Combined	Max of Viseme and Volume	Balanced	Uses whichever signal is stronger; catches both speech and non-speech sounds

Viseme mode is recommended for speech. It only opens the jaw for actual open-vowel sounds (AA), so the mouth stays closed for consonants like "M", "B", "S". Volume mode opens the jaw for any loud sound, including music, footsteps, or environmental noise playing through the same AudioSource.

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Auto-Detection

The Auto-Detect Jaw Bone button (and the Setup Wizard) searches the character's bone hierarchy for transforms with names containing:

• jaw, chin, mandible

• mouth_bone, bn_jaw, bip_jaw, def_jaw, bone_jaw

It prefers bones with lower or bot in the name and avoids bones named upper or lip.

If auto-detection fails, assign the jaw bone manually by dragging it from the hierarchy.

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Works with Text Lip Sync

The Jaw Bone Target also works with CrystalTextLipSync for text-driven lip sync (no audio needed). When CrystalTextLipSync writes viseme weights into the controller, the Jaw Bone Target reads the AA weight and opens the jaw accordingly.

This means the Jaw Bone Target works with:

• Audio lip sync (real-time FFT from AudioSource)

• Text lip sync (from CrystalTextLipSync)

• Microphone lip sync (from CrystalMicrophoneLipSync)

• Any integration (Game Creator 2, PixelCrushers Dialogue System, etc.)

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Editor Preview

The custom inspector includes:

• Auto-Detect Jaw Bone button ... finds the jaw bone in the hierarchy

• Live Debug View (Play Mode) ... shows a progress bar of the current jaw opening

• Test Pose slider (Edit Mode) ... preview the jaw rotation range without entering Play Mode

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Troubleshooting

Jaw doesn't move

1. Check that Controller and Jaw Bone are assigned in the inspector

2. Verify the controller's AudioSource has audio playing

3. Try Volume drive mode to confirm the bone rotates at all

4. Check that Max Angle is high enough to be visible (try 20°)

Jaw opens in the wrong direction

• Toggle Invert Direction in the inspector

• If still wrong, try a different Axis (X / Y / Z)

Jaw snaps open/closed too fast

• Reduce Smoothing Speed (try 10...15)

Jaw barely opens

• Increase Max Angle (try 20...30°)

• Increase Intensity (try 1.0)

• If using Volume mode, increase Volume Multiplier

Jaw opens for non-speech sounds

• Switch from Volume to Viseme drive mode ... it only responds to detected open-vowel sounds

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FAQ

Q: Can I use both Jaw Bone Target and Blendshape Target on the same character? A: Technically yes, but it rarely makes sense. If your character has blendshapes, use the Blendshape Target ... it produces far better results. The Jaw Bone Target is designed for characters without blendshapes.

Q: Does this work with Humanoid rigs? A: Yes. The component runs in LateUpdate after the Animator, so it overrides the Animator's jaw rotation correctly. Just make sure the jaw bone isn't locked by an Animation Override layer.

Q: What if my character has no jaw bone at all? A: You can use any transform as the "jaw bone" ... for example, the lower half of a split-face mesh, a puppet's lower jaw piece, or any hinged object. The component just rotates whatever transform you assign.

Q: Is there any performance difference? A: The Jaw Bone Target is slightly cheaper than the Blendshape Target ... it's a single Quaternion.Euler + assignment vs iterating 15 blendshape weights. Both are negligible.