Clouds Noise*

Introduction
Key Features
Parameters
Quick Recipes

Clouds Noise is a specialized procedural texture designed to simulate atmospheric density. Based on a classic "Clouds" implementation, it combines a soft Perlin-based fractal with a robust density-shaping engine. Unlike standard noise, this node includes built-in controls for soft-clipping, exponential contrast, and altitude fading, making it the go-to choice for generating smoke, fog, dry ice, and soft organic tissues without requiring complex ramp nodes. Performance wise and to best support GPU, it replaces LUTs with analytical hash functions.

Performance Cost 🟢 Low

Space 2D/3D - UV/World/Object

Implementation Native Compiled C++

Devices (Cycles) CPU / GPU (1:1)

Usage & Behavior

With default values

High constrast with well defined borders

High ratio rough noise for dirt crusts etc.

Stylized with NoiseTweaker and NoisePalette

This noise is distinct because of its "puffy" nature. It uses an internal sigmoid contrast curve to bunch values together, creating defined "clumps" separated by transparency. It also features a unique Depth parameter that fades the noise out along the Z-axis, simulating the thinning of atmosphere at height.

Best Used For: Cumulus clouds, steam, fog banks, moss patches, and volumetric density inputs.
Indicated also for: Hard surfaces like stone, rusty metals and crusty surfaces.

Key Features

Atmospheric Logic: Mimics the behavior of the classic Maya® Cloud texture.
Sigmoid Contrast: Exponential curve controls for soft, pillowy falloffs.
Altitude Fade: Built-in Z-axis attenuation for height-based effects.

Parameters

Invert (bool, default: false)

Inverts the final transparency output. Default behavior produces white clouds on black; inverting produces black holes in a white fog.

Coords Vector

The input texture coordinates. If left unconnected, defaults to Position (P).

Scale Vector (default: 2.0, 2.0, 2.0)

Global scaling factor. Larger values create smaller, denser cloud puffs.

Amplitude (default: 5.0)

The initial brightness/strength of the noise signal before shaping. High amplitude pushes more values into the "solid" range, making the clouds thicker.

Contrast (default: 0.2)

Controls the sharpness of the transition between cloud and sky.
- Low values: Very soft, uniform, misty fog.
- High values: Distinct, sharp-edged cumulus clouds.

Ratio (default: 0.7)

Also known as "Gain" or "Persistence." It controls how strong the fine details are relative to the large shapes.
- High Ratio: Crunchy, highly detailed clouds (stormy).
- Low Ratio: Soft, smooth blobs (cartoon clouds).

Edge Threshold (default: 0.5)

Determines the "coverage" of the clouds. It sets the midpoint value where the noise becomes visible. Increasing this makes the clouds larger and more dominant; decreasing it breaks them into smaller, isolated puffs.

Transparency Range (default: 0.5)

Defines the softness of the edge cutoff.
- 0.0: Binary transparency (hard cutout).
- 1.0: A long, smooth gradient from opaque to transparent (wispy).

Ripples Vector (default: 1.0, 1.0, 1.0)

Anisotropic scaling applied *before* the noise calculation. Use this to stretch the clouds in a specific direction (e.g., wind-blown cirrus clouds stretched on X).

Depth (default: 8.0)

Controls a vertical fade along the local Z-axis. The noise will fade from full strength at Z=0 to zero strength at Z=[Depth]. Useful for creating ground fog that naturally disappears as it rises.

Quick Recipes

Use these settings to sculpt different atmospheric conditions.

Ground Fog

Scale: 1.5
Contrast: 0.1
Transp. Range: 0.8
Depth: 5.0

Low contrast and high transparency range create a soft mist that fades out as it gets higher (Depth).

Storm Clouds

Amplitude: 8.0
Contrast: 0.6
Ratio: 0.8
Ripples: (2, 1, 1)

High amplitude and ratio create dense, detailed structures. Ripples stretch them slightly as if driven by wind.

Cartoon Puffs

Amplitude: 4.0
Contrast: 0.8
Ratio: 0.4
Edge Thresh: 0.6

High contrast but low ratio creates distinct shapes with smooth surfaces and very little internal detail.

Technical Note: The noise implements a fractional octave loop to allow for smooth animation of detail levels. The contrast shaping is performed using a sigmoid function: 1.0 / (1.0 + exp(-(sum - ctr) * c)).

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