This is a shader which evaluates a coherent noise function (potentially summed over several octaves, giving fractal noise, sometimes known as a turbulence function). The output is between 0 to 1 (actually [0,1)), which can be used as input to several other shader nodes to produce various effects. This is useful for creating many real-world patterns (marble, granite, leather, etc.)
The number of octaves over which the noise function is calculated (the fractal noise function is repeated at multiple frequencies, known as octaves; normally each octave is at about twice the frequency, i.e., half the size, of the previous one, but you can alter this with the lacunarity control).
Defines a degree of random displacement applied to each point as part of the noise calculation, giving a different aesthetic feel.
Controls the amplitude, or range, of the output. Normally the output has values between 0 and 1, the amplitude control multiplies this.
Controls the scale of the noise function in x, y, and z directions.
Specifies the coordinate space to use. These include World, Object and Pref space co-ordinates. Pref is short for 'vertex in reference pose'. The plugin can pass these vertices to Arnold (in addition to the regular, deformed vertices) which can in turn be queried by the noise shader so that the noise 'sticks' to the reference pose and does not swim as the mesh deforms.
- Object space, where points are expressed relative to the local origin (center) of the object.
- World space, where points are relative to the global origin of the scene.
- Pref, which isn’t really a space, but rather a reference to a bind pose (note Pref does not work with NURBS surfaces).
Below are animations that show Pref space coordinates in use with a deforming object. Note how the texture sticks to the object when using Pref space coordinates, compared to Object/World space coordinates where the texture swims.
Using World/Object Space - Texture Swims
Using Pref Space - Fixes Texture Swimming