Houdini 20.0 Nodes Geometry nodes

Cloud Wispy Noise geometry node

Applies thin feathery like fine displacement noise to a fog volume.

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Since 20.0

Overview

This will add a noise displacement pattern to a volume field in order to create a thin, wispy broken-up cloud like appearance. Various noise shaping options are available as well as masking controls. This node can also be used with a cloud volume displaced by Cloud Billowy Noise to add wispy details blown out from the cloud by the wind. By providing a surface volume on the second input, you can control the strength of the wispy details based on the distance of the cloud.

Inputs

Density Volume

Provides a source volume for the wispy displacement.

Surface Volume

The second input provides a signed distance field input that can be used to influence the overall wispy displacement. When working with a cloud generated by Cloud Billowy Noise, this allows you to control the wind strength that can be stronger the further away the voxel is from the cloud surface.

Note

Make sure the signed distance field has enough expanded activated voxels to cover the area of the wispy noise displacement.

Mask Volume

The third input provides an optional mask using the blend between the original input volume and the modified volume by this node.

Parameters

General

Mask

When this checkbox turned on, use the blend between the original input volume (given by Density Volume) and to modified volume by this node. Setting this value to 0 means that this node will not have an effect on the input volume. Optionally, you can provide a mask volume (given by Mask Volume) to mask specific regions in the volume field.

Invert Mask

Negates the fog volume mask from the second input, if any.

Iterations

Controls the number of displacement iterations. More iterations can create larger wispy displacement. Doing more than one iteration will slow down the cooking process.

Source on Each Pass

When this is turned on, the input volume is combined with the displaced volume in each iteration.

Substeps

The number of substeps to take in each iteration. Larger values can smooth out the fine details.

Override Look

Cloud Visualization

When this checkbox is on, overwrites the visualization for the volume.

Shading

Controls how to shade the volume. When generating cloud patterns, use Occlusion to see all the finer details and Reversed Occlusion to display clouds in a more realistic manner.

Ambient Occlusion

Uses ambient shadowing to display the volume.

Reversed Occlusion

Reverses the ambient shadowing for volumes which can be used to give a more realistic cloud look with internal scattering.

Density Scale

Fixed multiplier on the density field to control how opaque the volume is. If you are using a larger scene scale, you may need a smaller density scale.

Note

Fog density is density per unit length, and is independent of the resolution. So the same sized box, at 100 or 10 divisions, should be the same opacity. This means very small boxes will become transparent, especially if HDR rendering isn’t on. You can enable HDR rendering on the Scene tab of the Display Options dialog.

Setting the HDR Textures format to at least 16-bit for 3D textures can also help resolve low-density volumes. These settings can be found under the Texture tab of the Display Options.

Ambient Shadow Scale

Determines the intensity of self shadows from ambient light sources. The final amount of self-shadowing from these lights is controlled by the product of Density Scale, Shadow Scale, and Ambient Shadow Scale. The video demonstrates the value increasing from 0 to 1.

Note

Turning off this checkbox does not disable ambient shadowing. Instead, it keeps this property of the geometry unchanged. If no Ambient Shadow Scale is set, Ambient Occlusion on the Geometry tab of the Display Options controls the default amount of self-shadowing from ambient lights.

Note

The default headlight is treated as an ambient source by fog volumes.

Exposed Color

Color of smoke that’s receiving direct light from an ambient light source. The default white setting indicates that areas exposed to external lights are bright. You can set this darker than Occluded Color to achieve a more cloud-like look, where areas deeper within the cloud experience more light scattering and thus appear brighter. Set Ambient Colors must be enabled to control this parameter.

Occluded Color

Color of smoke that’s not receiving any light from an ambient light source. The default black setting indicates that areas occluded from light are dark. You can set this brighter than Exposed Color to achieve a more cloud-like appearance, where areas deeper within the cloud (that is, those occluded from outside light) are more luminous due to a greater degree of internal scattering. Set Ambient Colors must be enabled to control this parameter.

Wispy Noise

Noise

Noise Type

The type of noise to generate. Different algorithms give noise with different characteristics.

Fast

The default. A faster and more interesting variant of Perlin noise.

Sparse Convolution

Sparse Convolution noise is similar to Worley noise. Does not have artifacts at grid points.

Alligator

Produces a bumpy output. Named for its alleged resemblance to alligator skin.

Perlin

A noise where the visual details are the same size. Wikipedia article

Perlin Flow

A noise that’s stable over time, like a rotated Perlin noise, useful to create noise that seems to swirl and flow smoothly across time. Use the Flow rotation parameter below to control the rotation.

Simplex

A noise similar to Perlin but the noise lattice is on a tetrahedral mesh rather than a grid. This can avoid the grid patterns often visible in Perlin noise.

Worley Cellular F1

Produces cellular features similar to plant cells, ocean waves, honeycombs, cratered landscapes, and so on. Wikipedia article

Worley Cellular F2-F1

A variant of Worley noise that produces blunted and cornered features.

Manhattan Cellular F1

A variant of Worley F1 noise that uses Manhattan distance calculation. Useful when you want unusual-looking noise.

Manhattan Cellular F2-F1

A variant of Worley F2-F1 noise that uses Manhattan distance calculation. Useful when you want unusual-looking noise.

Chebyshev Cellular F1

A variant of Worley F1 noise that uses Chebyshev distance calculation. Useful when you want unusual-looking noise.

Chebyshev Cellular F2-F1

A variant of Worley F2-F1 noise that uses Chebyshev distance calculation. Useful when you want unusual-looking noise.

Perlin Cloud

Generates perlin noise based cloud pattern influenced by the Distortion parameter.

Perlin noise with Distortion set to -1 (left) and +1 (right):

Simplex Cloud

Generates simplex noise based cloud pattern influenced by the Distortion parameter. Simplex noise similar to Perlin, but the noise lattice is on a tetrahedral mesh rather than a grid. This can avoid the grid patterns often visible in Perlin noise.

Simplex noise with Distortion set to -1 (left) and +1 (right):

Fast Simplex Cloud

Generates fast simplex noise based cloud pattern influenced by the Distortion parameter. This simplex noise function uses a different lattice structure and a cheaper accumulation method.

Simplex noise with Distortion set to -1 (left) and +1 (right):

Amplitude

Controls the effect of the distortion, large values will create larger wispy details in the pattern, but might create unrealistic looking cloud patterns.

Click the Per Component button for separate amplitudes along each axis.

Component Scope

Specifies which vector components will be changed by the amplitude.

Amplitude Scale

When you turn on the Per Component button, this lets you scale the Amplitude separately across each axis.

Element Size

Uniform scale of elements in the noise.

Click the Per Component button for separate scales along each axis.

Element Scale

When you turn on the Per Component button, this lets you scale the Element Size separately across each axis.

Offset

Offset within the evaluated noise field (added to each axis). If you have the general noise effect you want, but want to get a different set of values for a different look, try changing the offset.

You can animate the noise using an expression such as $T * 0.25 here. This is faster to compute than Animate Noise, but gives the visual effect of “panning” across the noise field, which may or may not be acceptable.

Click the Per Component button for separate additional offsets along each axis.

Offset

When you turn on the Per Component button, this lets you add the a separate offset along each axis.

Fractal

Max octaves

The number of iterations of distortion to add to the output of the basic noise. The more iterations you add, the more “detailed” the output. Note that the output may have fewer octaves than this parameter (that is, increasing the parameter will eventually stop adding detail), because the node eventually stops when there’s no more room to add more detail in the output.

Roughness

The scale increment between iterations of fractal noise added to the basic output. The higher the value the larger the “jaggies” added to the output. You can use a negative value for roughness.

Step Size

Controls the resolution of the curl noise function used to generate the noise. A lower value will lead to tighter spirals in the noise.

Advection

Advect Noise

Advect Noise

Applies additional noise offset to the main noise to create finer details.

Noise Type

The type of noise to generate. Different algorithms give noise with different characteristics.

Fast

The default. A faster and more interesting variant of Perlin noise.

Sparse Convolution

Sparse Convolution noise is similar to Worley noise. Does not have artifacts at grid points.

Alligator

Produces a bumpy output. Named for its alleged resemblance to alligator skin.

Perlin

A noise where the visual details are the same size. Wikipedia article

Perlin Flow

A noise that’s stable over time, like a rotated Perlin noise, useful to create noise that seems to swirl and flow smoothly across time. Use the Flow rotation parameter below to control the rotation.

Simplex

A noise similar to Perlin but the noise lattice is on a tetrahedral mesh rather than a grid. This can avoid the grid patterns often visible in Perlin noise.

Worley Cellular F1

Produces cellular features similar to plant cells, ocean waves, honeycombs, cratered landscapes, and so on. Wikipedia article

Worley Cellular F2-F1

A variant of Worley noise that produces blunted and cornered features.

Manhattan Cellular F1

A variant of Worley F1 noise that uses Manhattan distance calculation. Useful when you want unusual-looking noise.

Manhattan Cellular F2-F1

A variant of Worley F2-F1 noise that uses Manhattan distance calculation. Useful when you want unusual-looking noise.

Chebyshev Cellular F1

A variant of Worley F1 noise that uses Chebyshev distance calculation. Useful when you want unusual-looking noise.

Chebyshev Cellular F2-F1

A variant of Worley F2-F1 noise that uses Chebyshev distance calculation. Useful when you want unusual-looking noise.

Perlin Cloud

Generates perlin noise based cloud pattern influenced by the Distortion parameter.

Perlin noise with Distortion set to -1 (left) and +1 (right):

Simplex Cloud

Generates simplex noise based cloud pattern influenced by the Distortion parameter. Simplex noise similar to Perlin, but the noise lattice is on a tetrahedral mesh rather than a grid. This can avoid the grid patterns often visible in Perlin noise.

Simplex noise with Distortion set to -1 (left) and +1 (right):

Fast Simplex Cloud

Generates fast simplex noise based cloud pattern influenced by the Distortion parameter. This simplex noise function uses a different lattice structure and a cheaper accumulation method.

Simplex noise with Distortion set to -1 (left) and +1 (right):

Amplitude

Controls the effect of the advection. Large values will advect the noise more. This is a multiplier on the noise amplitude (given by Amplitude).

Click the Per Component button for separate amplitudes along each axis.

Amplitude Scale

When you turn on the Per Component button, this lets you scale the Amplitude Scale separately across each axis.

Element Size

Uniform scale of elements in the noise. This is a multiplier on the noise element size (given by Element Size).

Click the Per Component button for a separate element size scale along each axis.

Element Scale

When you turn on the Per Component button, this lets you scale the Element Size separately across each axis.

Offset

Offset within the evaluated advection noise field (added to each axis). If you have the general noise effect you want, but want to get a different set of values for a different look, try changing the offset.

Click the Per Component button for a separate offset along each axis.

Offset

When you turn on the Per Component button, this lets you add a separate offset along each axis.

Fractal

Max Octaves

The number of iterations of distortion to add to the output of the basic noise. The more iterations you add, the more “detailed” the output. Note that the output may have fewer octaves than this parameter (that is, increasing the parameter will eventually stop adding detail), because the node eventually stops when there’s no more room to add more detail in the output.

Roughness

The scale increment between iterations of fractal noise added to the basic output. The higher the value the larger the “jaggies” added to the output. You can use a negative value for roughness.

Velocity

Wind

Add Wind

When this is turned on, a directional force is added to the generated wispy noise to simulate the effect of a directional wind.

Wind Strength

Controls the strength of the wind. Values that are too large could destroy the fine wispy details.

Wind Direction

Controls the direction of the wind force.

Scale by Surface Distance

Scale by Surface Distance

When you apply wind to billowy clouds (created by Cloud Billowy Noise), this allows scaling the strength of the wind based on the signed distance field (provided in the second input of this node). Using this, the wispy details can be pulled more and more toward the wind direction the further away they are from the surface of the cloud.

Distance Min

Controls the surface distance at which the wind strength is at zero.

Distance Max

Controls the surface distance at which the wind strength is at its maximum.

Use Control Ramp

Allows the Control Ramp to change how the surface distance should scale the wind strength between the minimum and maximum distance.

Control Ramp

The ramp’s vertical axis represents the strength of the effect and the horizontal axis represents the surface distance between Distance Min and Distance Max.

Reflect Velocity

Reflect Velocity

The generated wispy noise field produces vectors that can flow in all directions. When working with a billowy cloud, you might not want vectors pointing inwards in the cloud volume. When a signed distance surface is provided as the second input, this controls how much each vector should point towards the surface normal instead based on the distance from the cloud surface.

Distance Min

Controls the surface distance at which the reflection strength is at zero.

Distance Max

Controls the surface distance at which the reflection strength is at its maximum.

Use Control Ramp

Allows the Control Ramp to change how the surface distance should scale the reflection strength between the minimum and maximum distance.

Control Ramp

The ramp’s vertical axis represents the strength of the effect and the horizontal axis represents the surface distance between Distance Min and Distance Max.

Scale by Surface Distance

Scale by Surface Distance

Scales the overall strength of the wispy noise based on the distance from the cloud surface when a signed distance field is provided in the second input.

Distance Min

Controls the surface distance at which the wispy strength is at zero.

Distance Max

Controls the surface distance at which the wispy strength is at its maximum.

Use Control Ramp

Allows the Control Ramp to change how the surface distance should scale the wispy strength between the minimum and maximum distance.

Control Ramp

The ramp’s vertical axis represents the strength of the effect and the horizontal axis represents the surface distance between Distance Min and Distance Max.

Scale by Bounding Box

Scale by Bounding Box

Scales the overall strength of the wispy noise based on the distance along a bound direction.

Bound Direction

The direction in world space to use to scale the wispy noise strength.

Bound Min

Controls the bound limit along the bound direction (given by Bound Direction) at which the wispy strength is at zero.

Bound Max

Controls the bound limit along the bound direction (given by Bound Direction) at which the wispy strength is at its maximum.

Use Control Ramp

Allows the Control Ramp to change how the bound distance should scale the wispy strength between Bound Min and Bound Max.

Control Ramp

The ramp’s vertical axis represents the strength of the effect and the horizontal axis represents the bound distance between Bound Min and Bound Max.

Scale by Density

Scale by Density

Scales the overall strength of the wispy noise based on incoming density volume.

Density Min

Controls the incoming density value at which the wispy strength is at zero.

Density Max

Controls the incoming density value at which the wispy strength is at its maximum.

Use Control Ramp

Allows the Control Ramp to change how the incoming density value should scale the wispy strength between Density Min and Density Max.

Control Ramp

The ramp’s vertical axis represents strength of the effect and the horizontal axis represents the incoming density between Density Min and Density Max.

Bindings

Bindings

Density Volume

The name of the volume to be used as density for generating the wispy noise. Usually you should leave it as density.

Surface Volume Name

The name of the volume to be used as signed distance field for generating the wispy noise. Usually you should leave it as surface.

Mask Volume Name

The name of the volume to be used as mask generating the wispy noise. Usually you should leave it as mask.

See also

Geometry nodes