Octopus Camouflage Shader

A biologically-inspired camouflage shader for Unity's Built-in Render Pipeline that models how real octopus skin works.

How It Works

Real octopus skin has three layers of specialized cells that work together to produce rapid color change. This shader replicates each layer:

Leucophores (Bottom Layer) — White scattering cells that reflect ambient light wavelengths back, acting as a neutral backdrop. Controls: base color, ambient blend, intensity.

Iridophores (Middle Layer) — Stacks of reflective plates that produce iridescent blues, greens, and golds depending on viewing angle. Driven by fresnel (view-angle) calculations with adjustable hue range, shimmer speed, and scale.

Chromatophores (Top Layer) — Thousands of tiny elastic pigment sacs that expand and contract under neural control. Four independent pigment channels (red, yellow, brown, black) are each generated on their own offset Voronoi cell grid, giving each channel a unique organic pattern. Each channel has independent expansion, wave influence, and pigment color.

Wave Propagation — Octopus neurons fire in cascading sequences, creating visible ripples of color change across the skin. The shader supports radial and directional waves, dual-wave sources, per-channel wave sensitivity, and adjustable speed/frequency/decay.

Papillae — Muscle bundles that raise or smooth the skin to match surrounding textures. Implemented as vertex displacement plus normal perturbation using fractal noise.

Installation

1. Copy OctopusCamouflage.shader anywhere into your Unity project's Assets folder.
2. Copy OctopusCamouflageInspector.cs into an Editor folder (e.g. Assets/Editor/).
3. Optionally copy OctopusCamouflageController.cs anywhere into Assets if you want runtime scripting control.

Quick Start

1. Create a new Material in Unity.
2. Set the shader to Custom > OctopusCamouflage.
3. Assign your character's base texture to the Base Texture slot.
4. Click one of the Presets buttons in the inspector to see it in action.
5. Tweak from there.

Inspector Sections

Presets

One-click configurations to use as starting points:

Preset	Description
Resting	Calm state, minimal chromatophore activity, subtle breathing pulse
Alert	Heightened activity, fast waves, raised papillae
Sandy Camo	Warm yellows/browns blending toward a sand target color
Deep Ocean	Dark leucophore base, strong iridescence, no yellows
Coral Reef	Mixed pigments with heavy papillae for rough texture matching
Threat Display	Maximum expansion, fast dual waves, intense iridescence
Passing Cloud	The signature dark wave that octopuses send across their body
Reset All	Returns every parameter to its default value

Layer Blending

Controls how much each biological layer covers your base texture:

• Base Texture Visibility — How strongly the original texture comes through (1.0 = full).
• Leucophore / Iridophore / Chromatophore Opacity — Per-layer opacity. Lower chromatophore opacity to let base texture details show through the pigment cells.
• Camo Transition Opacity — How opaque the camouflage target color blend is.
• Chromatophore Blend Mode:
  • Replace — Pigment fully covers the base (original behavior).
  • Multiply — Pigment tints the base texture, preserving detail in light areas.
  • Overlay — Preserves base texture contrast while adding pigment color. Best for seeing details and camo simultaneously.

Chromatophore Layer

• Cell Scale — Size of the Voronoi cells (higher = smaller cells).
• Cell Edge Sharpness — How soft/hard the edge of each pigment sac is.
• Each pigment channel (Red, Yellow, Brown, Black) has:
  • Pigment Color — The color of the pigment. Alpha controls max opacity of that channel.
  • Expansion — 0 = fully contracted (invisible), 1 = fully expanded.
  • Wave Influence — How much this channel responds to the neural wave signal.

Wave Propagation

• Wave Origin — Center point of radial waves in UV space (0-1).
• Speed / Frequency / Amplitude — How fast, dense, and strong the wave is.
• Decay — How quickly the wave fades with distance from origin.
• Radial vs Directional — Toggle between expanding rings and sweeping planes.
• Secondary Wave — Enable a second independent wave source.

Camouflage Transition

• Target Color — The color the octopus is trying to match.
• Camo Blend — 0 = no camouflage, 1 = fully transitioned. Animate this for the full effect.
• Camo Pattern Noise — Assign a grayscale noise texture for organic transition edges.
• Pattern Scale / Contrast / Sharpness — Shape the transition pattern.

Papillae

• Bump Strength — How much the mesh vertices displace (0 = smooth skin).
• Scale — Size of the bump pattern.
• Sharpness — Higher = more peaked bumps, lower = rounder bumps.

Animation

• Global Speed — Master speed multiplier for all animation.
• Pulse Speed / Amount — Chromatophores rhythmically pulse like real octopus cells.
• Breathing Speed / Amount — Slow oscillation simulating the animal breathing.

Runtime Controller

Attach OctopusCamouflageController to any GameObject with a Renderer using this shader. It provides:

// Smooth transition to a built-in state
camo.TransitionToState(OctopusCamouflageController.StateSandyCamo, 2f);

// Instant snap
camo.SetStateImmediate(OctopusCamouflageController.StateAlert);

// Signature dark wave across the body
camo.TriggerPassingCloud(Vector2.right, speed: 3f, duration: 3f);

// Brief flash when startled or hit
camo.TriggerStartleFlash(flashDuration: 0.3f, recoverDuration: 1.5f);

// Set wave origin to a hit point (UV space)
camo.SetWaveOrigin(new Vector2(0.3f, 0.7f));

// Directly control a single pigment channel
camo.SetPigmentExpansion(
    OctopusCamouflageController.PigmentChannel.Red, 0.8f);

// Blend toward a terrain/environment color
camo.BlendToCamoColor(terrainColor, blend: 0.6f, duration: 1.5f);

Custom States

Create your own CamoState structs for game-specific scenarios:

var hidingState = new OctopusCamouflageController.CamoState
{
    redExpansion = 0.1f,
    yellowExpansion = 0.5f,
    brownExpansion = 0.6f,
    blackExpansion = 0.05f,
    waveAmplitude = 0.1f,
    waveSpeed = 0.3f,
    iridophoreStrength = 0.05f,
    papillaeStrength = 1.0f,
    camoBlend = 0.5f,
    chromatophoreOpacity = 0.6f,
    baseTextureStrength = 1.0f,
    targetColor = someEnvironmentColor,
    leucophoreColor = new Color(0.8f, 0.75f, 0.65f)
};

camo.TransitionToState(hidingState, 2.5f);

The transitionCurve field on the controller is a public AnimationCurve you can edit in the inspector to shape how transitions ease in/out.

Requirements

• Unity (Built-in Render Pipeline)
• Shader Target 3.5+

Tips

• For characters where you want the base skin/texture visible through the camo effect, set Chromatophore Opacity to 0.4–0.6 and use Overlay blend mode.
• Assign a Perlin or Simplex noise texture to the Camo Pattern Noise slot for organic-looking camouflage transition edges.
• The Passing Cloud preset recreates the dark traveling wave real octopuses use for communication — great for signaling mood in gameplay.
• All shader properties can be animated via Unity's Animation window or Timeline for cutscenes.
• Wave Origin is in UV space (0–1), so you can convert a raycast hit's textureCoord directly into a wave origin point.

License

MIT