Houdini 16.5 Nodes VOP nodes

Unified Noise VOP node

Presents a unified interface and uniform output range for all the noise types available in VEX.

On this page

This node lets you play with parameters on the Construction tab to design an interesting noise with 0-1 output, and then use the parameters on the Output tab to condition the output to the range you need.

This node is designed to have most of its interface promoted up to the parent material. to promote the UI for this node, you must choose Promote Interface ▸ UI + Links + Inputs to trigger scripts on the node to promote and create parameters up on the parent node.

Tip

The noise functions sometimes give artifacts or an area of static results around offset 0, so you want want to always begin designing your noise with non-zero values in the offset.

Inputs

The data type of the position (pos) input is controlled by the Signature parameter.

The VOP has inputs for dual positions (pos and pos2) and weights (kpos and kpos2). These fields are output by Pyro simulations when using dual rest fields. The weights allow you to indicate the current importance of each rest field. For example, if the first rest field is the most important, you would set kpos high and kpos2 low, and then as you gradually switch to the second rest field, lower kpos and raise kpos2. These values are output by DOPs.

Outputs

noise

The output of the noise function. The data type of this output is controlled by the Signature parameter.

x_avg

The calculated average of the noise.

x_oct

The actual number of octaves in the output. This may differ from the number of octaves requested in the parameters. For example, if you request 2000 octaves but the filtering of the output means that number of octaves can’t be used.

x_off

The offset of warping in the noise space.

Parameters

Signature

Sets the data types this node expects for the inputs, and the data type of the output. This allows you to integrate the noise with various other VOPs. If you choose a Noise type that doesn’t need this many components, the node will simply not use/set every component of the input/output.

Active

Whether to add noise to the input. When this checkbox is off value of Inactive Output is used as the noise output. This is useful for checking the effect of the node.

Inactive output

When Active is off, this value is used as the output instead of the noise function.

Frequency

The frequency of the noise. Higher values give smaller scaled details in the noise.

Offset

The offset of the input into the noise function. If you visualize the noise as a 2D graph or 3D height field, this has the effect of "panning" across the space of possible noise outputs. If you have the general noise effect you want but just want to get a different set of values for a different look, try changing the offset.

Period

For periodic noise types, the multiple of the input range before the noise pattern repeats.

Note

If Lacunarity is not 2, successive octaves will not have matching periods so a periodic noise won’t be built.

Construction

The output of the noise constructed by the parameters on this tab is always in the range 0 to 1. You can the condition the output, for example remap it to the range -1 to 1, using the parameters on the Output tab.

Noise type

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

Sinusoid

Not actually noise. This simply outputs a sine wave instead of adding noise to the input signal. This may be useful for debugging with an output that spans the entire 0-1 range.

Perlin

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

Periodic Perlin

A variant of Perlin noise with a repeating pattern. This can be useful for creating images, geometry, and motion that can be tiled and merged.

Simplex (Improved Perlin)

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.

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.

Periodic Flow

A variant of Flow noise with a repeating pattern. This can be useful for creating images, geometry, and motion that can be tiled and merged. Use the Flow rotation parameter below to control the rotation.

Worley (cellular) F1

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

Worley (cellular) F2

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

Alligator

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

Complement

Outputs the numerical complement (1 - x) of the computed noise. Basically turns the output upside-down.

Exponent

Raises the output to this exponent. For example, a value of 2 would square all output values. This has the effect of raising or lowering the values toward 1 or 0.

Lattice warp and gradient warp are two methods for adding "fractal-ness" to the basic noises by warping the noise space.

Enable Lattice Warp

Adds "stringiness" or "wiriness" to standard noise.

Accumulate Lattice Warp

When Lattice Warp is on, this accumulates the warp for each iteration (octave) of added fractal noise. When used in images, this can add interesting smudgy effects, and interesting landmarks when used for terrain.

Enable Gradient Warp

Widens the peaks or valleys of the noise output.

Accumulate Gradient Warp

When Gradient Warp is on, this accumulates the warp for each iteration (octave) of added fractal noise.

Flow Rotation

The rotation of the "swirl" when Noise type is "Flow", from 0 to 1. Because this parameter is fractional, you can’t just use $F to animate it, since all integral values will look the same, representing a complete revolution.

The fractal controls let you add additional fractal noise on top of the output of the basic noise type.

Fractal Type

None

Does not add any additional noise on top of the basic noise.

Standard

Adds pseudo-random noise on top of the basic output.

Terrain

Adds noise like "Standard" but dampens the noise in the valleys, which can be useful for generating mountainous terrain.

Hybrid

Like terrain, but with more sharpness in the valleys.

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.

Output

The output generated using the parameters on the Construction tab is guaranteed to be in the range 0-1. If you need different output, you can use the parameters on this tab to conveniently condition the output without messing with your noise parameters.

Fold

"Flips" values below the median to be above the median, so all valleys become peaks. (Note it flips across the median, not 0.) If the median is 0, this is like taking the absolute value.

Bias

Moves the output down or up toward 0 or 1.

Gain

Increases or decreases the contrast from 0.5 in the output.

Complement

Outputs the numerical complement (1 - x) of the computed noise. Basically turns the output upside-down.

Output range (clamped)

Enables the New minimum and New maximum parameters to allow you to map the noise, which is normally in the [0,1] range, to a different range of values.

New minimum

Remaps the output so 0 values become this value.

New maximum

Remaps the output so 1 values become this value.

Final amplitude

Scales the final conditioned output up or down.

Filter Scale

A scale on the filter width to use in shading a shading context.

VOP nodes