Simulate Modifier

The Simulate modifier adds physics-based hair dynamics. Hair responds to gravity, wind, and collisions with realistic motion.

What It Does

The Simulate modifier brings hair to life with:

Physics simulation — gravity, inertia, momentum
Body collision — hair bounces off the scalp and body
Self-collision — strands don't pass through each other
Wind and turbulence — natural air forces
Timeline sync — scrub through animation with frame caching
Alembic baking — export simulation to disk for instant playback

Playback Controls

| Button | Action | |--------|--------| | Play | Start/stop simulation (toggle) | | Reset | Return to rest pose, clear state | | Step | Advance one frame manually | | Sync to Timeline | Sync simulation with Blender's timeline | | Bake to Alembic | Pre-simulate all frames to disk | | Clear | Free baked cache data |

The frame counter shows the current simulation frame.

Solver Section

Substeps

Simulation steps per frame.

Range: 1–20 (Default: 5)

More substeps = more stable, slower. Increase if hair explodes or jitters.

Iterations

Constraint solver iterations per substep.

Range: 1–60 (Default: 20)

More iterations = stiffer, more accurate. Increase for stiff hair.

Forces Section

Gravity

Gravity strength (m/s²).

Range: 0.0–20.0 (Default: 9.81)

Damping

How quickly motion dies down.

Range: 0.0–1.0 (Default: 0.1)

Higher = less bouncing, more stable. Increase if hair oscillates too much.

Wind

Wind force strength.

Range: 0.0–10.0 (Default: 0.0)

Air Drag

Air resistance.

Range: 0.0–0.5 (Default: 0.01)

Turbulence

Wind chaos and variation.

Range: 0.0–5.0 (Default: 0.0)

Creates natural swirling motion in the wind.

Turbulence Frequency

How fine the turbulence pattern is.

Range: 0.1–10.0 (Default: 1.0)

Stiffness Section

Stretch

Resistance to stretching (compliance value — lower = stiffer).

Range: 0.0–0.01 (Default: 0.00001)

Very low values make strands nearly inextensible.

Bend

Resistance to bending (compliance value — lower = stiffer).

Range: 0.0–0.1 (Default: 0.001)

Lower = stiffer hair. Higher = floppy hair.

Stretch Damp

Damping for stretch oscillation.

Range: 0.0–0.5 (Default: 0.01)

Bend Damp

Damping for bend oscillation.

Range: 0.0–1.0 (Default: 0.1)

Attract

Attraction back to rest shape.

Range: 0.0–1.0 (Default: 0.0)

Higher values make hair return to its styled shape during simulation.

Collision Section

Collision Mesh

Automatically uses the scalp/body mesh. Click "Pick" to select a different collision mesh.

Radius

Hair thickness for collision detection.

Range: 0.001–0.02 (Default: 0.003)

Increase if hair penetrates surfaces.

Friction

Surface friction.

Range: 0.0–1.0 (Default: 0.3)

0.0 = slippery, 1.0 = sticky.

Self-Collision (Edge-Edge)

Prevents strands from passing through each other. Expensive but realistic.

Default: Unchecked

Self Friction

Friction between strands during self-collision.

Range: 0.0–1.0 (Default: 0.2)

Ground Plane

Enable a flat ground plane for collision.

Default: Unchecked

Ground Z

Height of the ground plane.

Range: -2.0–2.0 (Default: 0.0)

Advanced Section

FTL (Follow-the-Leader)

Inextensibility correction strength.

Range: 0.0–1.0 (Default: 0.0)

Higher values prevent stretching more aggressively.

Collision Passes

Number of collision resolution passes per substep.

Range: 1–10 (Default: 3)

Self-Collision Passes

Number of self-collision resolution passes.

Range: 1–10 (Default: 5)

Settle

Number of frames to settle at start (pre-simulation).

Range: 0–30 (Default: 0)

Practical Examples

Basic Gravity Drape

Substeps: 5, Iterations: 20
Gravity: 9.81, Damping: 0.1
Stretch: 0.00001, Bend: 0.001

Hair falls naturally under gravity.

Stiff Hair (Short Hair)

Substeps: 5, Iterations: 30
Bend: 0.0001 (very stiff)
Attract: 0.3 (returns to style)
Damping: 0.2

Floppy Hair (Long Hair)

Substeps: 8, Iterations: 20
Bend: 0.01 (floppy)
Damping: 0.05

Windy Scene

Wind: 3.0
Turbulence: 1.5
Turb Freq: 2.0
Air Drag: 0.05

Tips

Start with defaults. Substeps 5, Iterations 20 works for most cases.
Increase Substeps if hair explodes or jitters.
Lower Bend compliance for stiffer hair, higher for floppy hair.
Use Attract to preserve styled shape during motion.
Self-collision is expensive. Only enable when needed.
Bake to Alembic for instant playback of complex simulations.
Sync to Timeline to scrub through cached frames.

Common Issues

| Problem | Solution | |---------|----------| | Hair explodes | Increase Substeps (try 8–12), increase Damping | | Hair penetrates body | Increase Collision Radius, increase Coll Passes | | Simulation too slow | Disable Self-Collision, reduce Substeps | | Hair too floppy | Decrease Bend compliance, increase Attract | | Hair too stiff | Increase Bend compliance | | Hair stretches | Decrease Stretch compliance, increase FTL |

Placement in Stack

Simulate should always be the last modifier:

1. Clumping
2. Coil
3. Frizz
4. Cut
5. Surface Offset
6. Simulate  ← always last