ZenDyn Documentation / Facial Dynamics and Magic

ZenDyn Facial Dynamics and Magic

ZenDyn adds controllable secondary motion to MetaHuman facial animation. Dynamics react to incoming movement, while Magic adds deterministic procedural motion for creative effects.

How The Controls Work Together

Regional Weight and Smoothing shape the base facial performance. Dynamics reacts to that performance with secondary motion, while Magic adds optional creative movement. Each remains independently adjustable so dialogue and authored expressions can be preserved.

Facial Regions

ZenDyn provides independent settings for:

• Brows
• Nose
• Cheeks
• Mouth
• Jaw
• Eyes

Each region has its own Dynamics and Magic controls. This allows subtle cheek response without affecting the mouth, or brow motion without changing the eyes.

Dynamics

Dynamics adds secondary positional movement in response to animation.

Recommended Starting Workflow

1. Enable Dynamics for one region.
2. Set Strength to a low value.
3. Play representative facial animation.
4. Increase Strength until the response becomes visible.
5. Increase Damping if motion continues for too long.
6. Increase Stiffness if the region drifts too far from the authored pose.
7. Add Smoothing only when the result needs a softer response.
8. Repeat for the remaining regions.

Controls

• Enable turns secondary motion on for the region.
• Strength controls the amount of generated motion.
• Damping removes velocity over time. Higher values settle more quickly.
• Stiffness pulls the result back toward the incoming animation.
• Gravity adds directional acceleration to the generated motion.
• Iterations controls simulation quality and stability. Higher values require more processing.
• Smoothing Amount smooths the generated positions.
• Increasing Interp Speed controls smoothing while motion increases.
• Decreasing Interp Speed controls smoothing while motion decreases.

Magic

Magic applies a deterministic procedural displacement pattern. It is disabled in the bundled presets so users can enable it intentionally.

Field Types

• None: No procedural field.
• Sine Ripple: Repeating wave motion.
• Ocean: Layered flowing movement.
• Pulse: Rhythmic expansion and return.
• Noise Drift: Slowly varying irregular movement.
• Turbulence: More energetic multi-directional movement.
• Spiral: Rotating phase progression.
• Breath: Breath-like periodic movement.

Controls

• Field Amount controls overall influence.
• Field Amplitude sets maximum displacement along the local axes.
• Field Frequency controls pattern density.
• Field Speed controls playback speed.
• Field Spacing offsets the phase through the hierarchy.
• Random Phase Amount adds deterministic variation between bones.
• Random Seed reproduces the same variation.

Regional Weight and Smoothing

The Control category adjusts the base animation for each facial region:

• 0% neutralizes the selected region’s contribution.
• 100% preserves the complete incoming regional expression.
• Values above 100% boost the regional expression from neutral, up to 200%.
• Regional smoothing softens changes in the base regional animation.

These controls do not change the strength used by the later Dynamics or Magic simulation. A region at 0% can still receive deliberately enabled bone dynamics.

Dialogue Guidance

The mouth and jaw carry speech-critical motion.

• Begin with low Mouth and Jaw dynamics strength.
• Keep Mouth and Jaw regional weights at 100% when the complete lip-sync performance must be preserved.
• Increase damping when secondary motion competes with phonemes.
• Use stiffness to keep the result close to the incoming performance.
• Reduce Mouth or Jaw Dynamics Strength before reducing the corresponding Control weight.
• Test with the actual dialogue animation, not only a neutral preview.

Reset

Simulation resets automatically after hierarchy changes and large playback jumps. To restart a region manually, disable and re-enable its Dynamics or Magic effect. Custom Control Rig setups can also use the individual simulation node’s Reset input.

Determinism

Magic uses its Random Seed to reproduce per-bone variation. Bundled defaults and presets use seed 33.

Dynamics uses a fixed simulation step for consistent damping across frame rates. The result still depends on the input animation and settings; different animation sampling can produce small differences.

ZenBlink Integration

Attach ZenBlink and ZenDyn to the same actor. Integration is automatic: ZenBlink manages the shared facial animation settings, while ZenDyn retains regional Control, Dynamics, and Magic. Duplicate shared categories are hidden in ZenDyn during combined use.