Houdini 20.5 Nodes Geometry nodes

Sky Field Pattern geometry node

Modifies a Sky Field using a 2D cloud pattern.

On this page
Since 20.0

Overview

This node creates noise patterns in a Sky Field volume. This is similar to the Sky Field Noise node, but this node has higher-level, more cloud-specific parameters and presets. For example, you can add a cumulus cloud pattern in your scene. See How to create a sky for how to use the Sky Field Pattern node to add cloud patterns.

Internally, this node uses the Volume Noise Fog SOP to apply noise created by the Cloud Noise VOP, Undulatus VOP, Fibratus VOP, Floccus VOP, and Fractus VOP.

This node ignores the thickness of the clouds.

Parameters

Layers

Pattern Layer

The name of the volume to apply the noise to.

The default value is sky.

Mask Layer

If a mask volume is wired into the node’s second input, this specifies which volume in the second input to use to mask this node’s effect, usually mask. Click the Add a Mask Paint button to paint the mask in the viewport, which automatically wires a Paint node into the second input.

The default value is skymask.

Blend

If a mask volume is wired into the node’s second input, this blends between the original input and the noise. When this is 0, this node does nothing and just passes through the original input. When this is 1, this node replaces the input with the noise.

The default value is 1.

General

Operation

Specifies how to combine the generated adjustment value with the incoming volume. If the target primitive does not exist on the input geometry, all operations will have the same effect.

Set

Use this operation if you want to overwrite any existing value with the generated adjustment value.

Add

The generated adjustment value will be added to the existing volume primitive.

Subtract

The generated adjustment value will be subtracted from the existing volume primitive.

Multiply

The existing volume primitive value will be multiplied by the generated adjustment value.

Minimum

Output will be minimum of the existing volume primitive value and the adjustment value.

Maximum

Output will be maximum of the existing volume primitive value and the adjustment value.

Sky Pattern

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

Cumulus

Creates a cumulus cloud pattern.

Fractus

Creates a ragged and fragmented ( fractus ) cloud pattern.

Floccus

Creates a floccus cloud pattern that resembles tufts of wool.

Fibratus

Creates a thin, fibratus cloud pattern.

Undulatus

Creates a wavy, undulatus cloud pattern.

Rotation

Rotates the pattern around using the normal vector of the Sky Field.

Cumulus

Cumulus Pattern

Noise Type

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

Alligator

Produces a bumpy output, similar to alligator skin. While this node is not distorted by the fractal iterations, it is useful to create finer bumpy cloud details.

Perlin

Noise where the visual details are the same size. Wikipedia article

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

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

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):

Element Size

Uniform scale of elements in the noise.

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

Element Scale

Turn on the Per Component button to 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.

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

Offset

Turn on the Per Component button to add the a separate offset along each axis.

Worley Details

Add Worley Details

When turned on, a worley noise is combined with the noise pattern (specified by Noise Type) to give puffy cloud noise. Enabling this, will largely diminish the distortion effect (specified by Distortion).

Noise pattern with added worley noise:

Blend

Controls the amount of mixing between the noise pattern (specified by Noise Type) and the worley noise. A value of 0 means no worley noise is applied to the noise pattern.

Erosion

Controls how fast the edges of the noise pattern turn to zero. The larger the value, the more the edges are eroded creating smaller and smaller cloud patches.

Element Size Scale

Multiplier on the Element Size parameter that effects the worley noise pattern.

Value Correction

Bias

This value controls how much the medium grey (noise values around 0.5) is pulled towards zero (if Bias is less than 1) or pulled towards one (if Bias is greater than 1). A value of 0.5 leaves the noise values unaffected.

Gain

Controls how much the medium greys (noise values around 0.5) are pulled together, while values around 0 and 1 are pulled apart. The value of 0.5 leaves the noise values unaffected.

Gamma

Controls the overall gamma of the generated noise. Values less than 1 will darken the noise, increasing the range of values in originally bright areas. Conversely, values greater than 1 will stretch out the range of values for originally dark areas, which will increase the overall brightness of the noise.

Contrast

This value expands or shrinks the overall range of tonal values. Particularly, each noise value is pushed towards (if Contrast is less than 1) or away from (if Contrast is greater than 1) medium grey (noise values at 0.5).

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.

Lacunarity

The frequency increment between iterations of fractal noise added to the basic output. Note that you can use a negative value.

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.

Warping

Distortion

Controls how much the noise is distorted in the direction of decreasing noise values if Distortion is greater than 1, and in the direction of increasing noise values if Distortion is less than 1. When worley details are added to the noise pattern, the effect of distortion are largely diminished.

Distortion with a value of 1:

Distortion with a value of -1:

Stretch

How much to stretch the noise in each direction. The advantage of using this instead of Element Size is that it preserves some details unstretched, making the stretched noise pattern more natural looking.

Comparing Element Scale of 3 (left) to Stretch value of 3 (right) along the X-axis:

Droop

Warps the generated noise such that the noise pattern is bending or hanging towards the given droop direction.

Noise pattern without (left) and with droop applied (right):

Droop Direction

The direction in which the noise is warped.

Fold

Remaps the values between -1 and 1 and flips values below 0 to the positive range, so all valleys become peaks.

Fractus

Fractus Pattern

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, you are able to 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, you are able to add a separate offset along each axis.

Wispy 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.

Frequency is scaled by 1.25.

Sparse Convolution

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

Frequency is scaled by 1.25.

Alligator

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

Frequency is scaled by 1.64.

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.

Wispy Strength

Controls the amount of wispy noise distortion.

Billowy Details

Billowy Details

Changes the large wispy cloud details into more billowy like patterns.

Fractus noise with Billowy Details disabled (left) and enabled (right):

Billowy Strength

Controls the amount of billowy noise in the pattern. Use this parameter in relation to the Wispy Strength control to create more interesting mixed patterns.

Worley Details

Add Worley Details

When turned on, a worley noise is combined with the noise pattern (specified by Noise Type) to give puffy cloud noise. Enabling this, will largely diminish the distortion effect (specified by Distortion).

Noise pattern with added worley noise:

Blend

Controls the amount of mixing between the noise pattern (specified by Noise Type) and the worley noise. A value of 0 means no worley noise is applied to the noise pattern.

Erosion

Controls how fast the edges of the noise pattern turn to zero. The larger the value, the more the edges are eroded creating smaller and smaller cloud patches.

Element Size Scale

Multiplier on the Element Size parameter that effects the worley noise pattern.

Value Correction

Gamma

Controls the overall gamma of the generated noise. Values less than 1 will darken the noise, increasing the range of values in originally bright areas. Conversely, values greater than 1 will stretch out the range of values for originally dark areas, which will increase the overall brightness of the noise.

Contrast

This value expands or shrinks the overall range of tonal values. Particularly, each noise value is pushed towards (if Contrast is less than 1) or away from (if Contrast is greater than 1) medium grey (noise values at 0.5).

Fractal

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.

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.

Lacunarity

The frequency increment between iterations of fractal noise added to the basic output. Note that you can use a negative value.

Warping

Distortion

Controls how much the noise is distorted in the direction of decreasing noise values if Distortion is greater than 1, and in the direction of increasing noise values if Distortion is less than 1. When worley details are added to the noise pattern, the effect of distortion are largely diminished.

Distortion with a value of 1:

Distortion with a value of -1:

Stretch

How much to stretch the noise in each direction. The advantage of using this instead of Element Size is that it preserves some details unstretched, making the stretched noise pattern more natural looking.

Comparing Element Scale of 3 (left) to Stretch value of 3 (right) along the X-axis:

Droop

Warps the generated noise such that the noise pattern is bending or hanging towards the given droop direction.

Noise pattern without (left) and with droop applied (right):

Droop Direction

The direction in which the noise is warped.

Fold

Remaps the values between -1 and 1 and flips values below 0 to the positive range, so all valleys become peaks.

Floccus

Floccus Pattern

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, you are able to 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 a separate offset along each axis.

Density Cutoff

Controls the density of the noise pattern. Increase the value to generate smaller patterns.

Wispy Details

Wispy Details

Adds small scale wispy cloud like distortion to the noise pattern.

Floccus noise with Wispy Details disabled (left) and enabled (right):

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.

Frequency is scaled by 1.25.

Sparse Convolution

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

Frequency is scaled by 1.25.

Alligator

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

Frequency is scaled by 1.64.

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.

Wispy Strength

Controls the amount of wispy noise distortion. Increase this value to break up a floccus pattern with small scale wispy details.

Worley Details

Add Worley Details

When turned on, a worley noise is combined with the noise pattern (specified by Noise Type) to give puffy cloud noise. Enabling this, will largely diminish the distortion effect (specified by Distortion).

Noise pattern with added worley noise:

Blend

Controls the amount of mixing between the noise pattern (specified by Noise Type) and the worley noise. A value of 0 means no worley noise is applied to the noise pattern.

Erosion

Controls how fast the edges of the noise pattern turn to zero. The larger the value, the more the edges are eroded creating smaller and smaller cloud patches.

Element Size Scale

Multiplier on the Element Size parameter that effects the worley noise pattern.

Value Correction

Gamma

Controls the overall gamma of the generated noise. Values less than 1 will darken the noise, increasing the range of values in originally bright areas. Conversely, values greater than 1 will stretch out the range of values for originally dark areas, which will increase the overall brightness of the noise.

Contrast

This value expands or shrinks the overall range of tonal values. Particularly, each noise value is pushed towards (if Contrast is less than 1) or away from (if Contrast is greater than 1) medium grey (noise values at 0.5).

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.

Lacunarity

The frequency increment between iterations of fractal noise added to the basic output. Note that you can use a negative value.

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.

Warping

Distortion

Controls how much the noise is distorted in the direction of decreasing noise values if Distortion is greater than 1, and in the direction of increasing noise values if Distortion is less than 1. When worley details are added to the noise pattern, the effect of distortion are largely diminished.

Distortion with a value of 1:

Distortion with a value of -1:

Stretch

How much to stretch the noise in each direction. The advantage of using this instead of Element Size is that it preserves some details unstretched, making the stretched noise pattern more natural looking.

Comparing Element Scale of 3 (left) to Stretch value of 3 (right) along the X-axis:

Droop

Warps the generated noise such that the noise pattern is bending or hanging towards the given droop direction.

Noise pattern without (left) and with droop applied (right):

Droop Direction

The direction in which the noise is warped.

Fold

Remaps the values between -1 and 1 and flips values below 0 to the positive range, so all valleys become peaks.

Fibratus

Fibratus Pattern

Element Size

Uniform scale of elements in the noise.

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.

Trail Length

Stretches out the fiber details. Larger values will make the pattern less noise, and more parallel aligned.

Trail Width

Controls the width and the spacing of the fiber pattern.

Cutoff Density

Controls the density of the noise pattern. Increase the value to generate smaller patterns.

Distort Trails

Distort Trails

Distorts the fiber pattern with spacial noise to create varying wave pattern features over a large landscape.

Amplitude

Controls the effect of the distortion. Large values will create larger twists and turns in the pattern, but might create unrealistic looking cloud patterns.

Element Size Scale

Uniform scale of elements in the distortion noise. This scale is relative to Element Size which controls the overall pattern size.

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.

Attenuation

Flattens the noise to prevent extreme spikes by damping the values. Higher values create a smoother look.

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.

Undulatus

Undulatus Pattern

Element Size

Uniform scale of elements in the noise.

Phase

Offsets the direction of the wave patterns along their facing direction. Use this to move patterns to a desirable location. With each increased unit value, each wave takes the place of its forward pattern.

Relative Thickness

Controls the relative width of each wave. Lower the value to create thinner trails.

Blur

Smooths the front side of the wave patterns.

Mirror Pattern

If mirroring of ramps is turned on, the ramps will alternate in slope forming tent functions.

Distort Waves

Distort Wave Pattern

Distorts the otherwise simple ramp patterns into a wave like pattern using spacial noise.

Amplitude

Controls the effect of the distortion. Large values will create larger distortion, but might create unrealistic looking cloud patterns. Similarly, lowering the value too much reveals the underlying simplistic ramp pattern.

Element Size Scale

Uniform scale of elements in the distortion noise. This scale is relative to Element Size which controls the overall pattern size.

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, you are able to 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.

Lacunarity

The frequency increment between iterations of fractal noise added to the basic output. Note that you can use a negative value.

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.

Warping

Distortion

Controls how much the noise is distorted in the direction of decreasing noise values if Distortion is greater than 1, and in the direction of increasing noise values if Distortion is less than 1. When worley details are added to the noise pattern, the effect of distortion are largely diminished.

Distortion with a value of 1:

Distortion with a value of -1:

Stretch

How much to stretch the noise in each direction. The advantage of using this instead of Element Size is that it preserves some details unstretched, making the stretched noise pattern more natural looking.

Comparing Element Scale of 3 (left) to Stretch value of 3 (right) along the X-axis:

Droop

Warps the generated noise such that the noise pattern is bending or hanging towards the given droop direction.

Noise pattern without (left) and with droop applied (right):

Droop Direction

The direction in which the noise is warped.

See also

Geometry nodes