Houdini 22.0 Nodes VOP nodes

Curl Noise 2D VOP node

Creates divergence-free 2D noise using a curl function.

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Since 10.0

This operator generates divergence-free 2D noise, computed using a curl function on standard Perlin noise. The operator can handle intervening geometry, allowing the noise field to “flow” around the given object.

The inputs of the Curl Noise operator have the same effect as their counterparts in the Turbulent Noise operator. The four new inputs are Step Size (h), Surface Effect Radius (d), Distance to Surface (dist).

Inputs

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

Outputs

noise

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

Parameters

Noise type

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

Perlin Noise

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

Sparse Convolution Noise

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

Alligator Noise

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

Frequency is scaled by 1.64.

Simplex Noise

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.

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.

Amplitude

Controls the noise’s minimum and maximum values. When you think of noise as a curve, the parameter controls the height of the peaks and valleys.

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.

Attenuation

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

Turbulence

Controls the degree of noise. Higher values create a more chaotic and less smooth look, with more peaks and valleys.

Step Size

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

Surface Effect Radius

Determines the magnitude of the effect that intervening geometry has on the created noise field. A higher value causes greater disturbances resulting from intervening geometry.

Distance to Surface

The signed distance value indicating the distance from the current position to the closest surface of intervening geometry. Piping in the result of a signed distance field with respect to a piece of geometry will allow the generated noise to react appropriately to that surface geometry.

Collision SDF

The file to load a collision field from. This will override the normal and distance values, instead, those values will be computed directly from the first volume primitive in the file. This allows the distances to vary within the noise computation, producing more accurate boundaries than if only a single sample is provided. Note the file does not have to be a disk file, it can also be an op: reference to a node or an opinput: reference to an input.

See also

VOP nodes