.. index:: Geometry Nodes; Noise Texture

******************
Noise Texture Node
******************

.. note::

   This node is ported from shader nodes. The manual and images are
   referencing the shader version of the node.
   This node accepts field inputs and outputs.
   When not connected the Vector input has an implicit ``position`` attribute value.

.. figure:: /images/node-types_ShaderNodeTexNoise.webp
   :align: right
   :alt: Noise Texture Node.

The *Noise Texture* node evaluates a fractal Perlin noise at the input texture coordinates.
It can be used for a single Perlin noise evaluation, or for combining multiple octaves
(layers) with increasingly finer detail.


Inputs
======

The inputs are dynamic, they become available if needed depending on the node properties.

Vector
   Texture coordinate to evaluate the noise at;
   defaults to *Generated* texture coordinates if the socket is left unconnected.
W
   Texture coordinate to evaluate the noise at.
Scale
   Scale of the base noise octave.
Detail
   Number of noise octaves.
   The fractional part of the input is multiplied by the magnitude of the highest octave.
   Higher number of octaves corresponds to a higher render time.
Roughness
   Blend between a smoother noise pattern, and rougher with sharper peaks.
Lacunarity
   The difference between the scale of each two consecutive octaves.
   Larger values corresponds to larger scale for higher octaves.
Offset
   An added offset to each octave, determines the level where the highest octave will appear.
Gain
   An extra multiplier to tune the magnitude of octaves.
Distortion
   Amount of distortion.


Properties
==========

Dimensions
   The dimensions of the space to evaluate the noise in.

   :1D: Evaluate the noise in 1D space at the input *W*.
   :2D: Evaluate the noise in 2D space at the input *Vector*. The Z component is ignored.
   :3D: Evaluate the noise in 3D space at the input *Vector*.
   :4D: Evaluate the noise in 4D space at the input *Vector* and the input *W* as the fourth dimension.

   .. note::

      Higher dimensions corresponds to higher render time,
      so lower dimensions should be used unless higher dimensions are necessary.

Normalize
   If enabled, ensures that the output values stay in the range 0.0 to 1.0.
   When disabled, output values are in the range -1.0 to 1.0.


Type
   Type of Noise texture, with different ways to combine octaves.

   :FBM:
      Fractal Brownian motion, produces a homogeneous and isotropic result.
      Values from octaves are added together.
   :Multifractal:
      More uneven, varying by location similar to real terrain.
      Values from octaves are multiplied together.
   :Hybrid Multifractal:
      Creates peaks and valleys with different roughness values, like real mountains rise out of flat plains.
      Combines octaves using both addition and multiplication.
   :Ridged Multifractal:
      Creates sharp peaks. Calculates the absolute value of the noise,
      creating "canyons", and then flips the surface upside down.
   :Hetero Terrain:
      Similar to *Hybrid Multifractal* creates a heterogeneous terrain, but with the likeness of river channels.


Outputs
=======

Factor
   Value of fractal noise.
Color
   Color with different fractal noise in each component.


Examples
========

.. figure:: /images/render_shader-nodes_textures_noise_example.jpg

   Noise Texture with high detail.

.. list-table:: Different Noise types with the same parameters.

   * - .. figure:: /images/render_shader-nodes_textures_musgrave_example-type-fbm.jpg
          :width: 320px

          fBM (fractal Brownian Motion).

     - .. figure:: /images/render_shader-nodes_textures_musgrave_example-type-multifractal.jpg
          :width: 320px

          Multifractal.

   * - .. figure:: /images/render_shader-nodes_textures_musgrave_example-type-hybrid.jpg
          :width: 320px

          Hybrid Multifractal.

     - .. figure:: /images/render_shader-nodes_textures_musgrave_example-type-terrain.jpg
          :width: 320px

          Heterogeneous Terrain.

   * - .. figure:: /images/render_shader-nodes_textures_musgrave_example-type-ridged.jpg
          :width: 320px

          Ridged Multifractal.

     - ..


Notes
=====

While the noise is random in nature, it follows a certain pattern that might not evaluate to
random values in some configurations. For instance, consider the following configuration
where a grid of objects have a material that evaluates a noise texture at their locations.
One might expect the objects to have random values since they have different locations,
but this is not the case.

.. figure:: /images/render_shader-nodes_textures_noise_issue-constant-value.png

   An example configuration where the noise evaluates to a constant value.

It seems all objects have a value of 0.5. To understand why this happens, let us
look at the following plot of a 1D noise texture.

.. figure:: /images/render_shader-nodes_textures_noise_1d-noise-plot.png

   A plot of a 1D noise with zero details and zero distortion.

The horizontal line denotes a value of 0.5 and the vertical lines denotes whole numbers assuming
a noise scale of 1. As can be seen, the noise always intersects the 0.5 line at whole numbers.
Since the aforementioned objects were distributed on a grid and have whole number locations,
they all evaluate to 0.5. Which explains the issue at hand.

Generally, any discrete evaluation of noise at integer multiples of the reciprocal of
the noise scale will always evaluate to 0.5. It also follows that evaluations closer to
that will have values close to 0.5. In such cases, it is almost always preferred to use
the White Noise Texture.

Regardless, one can mitigate this issue in a number of ways:

- Adjust the scale of the noise to avoid aligning the noise with the evaluation domain.
- Add an arbitrary offset to the texture coordinates to break the alignment with the evaluation domain.
- Evaluate the noise at a higher dimension and adjust the extra dimension
  until a satisfactory result is achieved.

.. list-table::

   * - .. figure:: /images/render_shader-nodes_textures_noise_issue-constant-value.png

          Constant value issue.

     - .. figure:: /images/render_shader-nodes_textures_noise_solution1-constant-value.png

          Mitigating the issue by adjusting the scale.

   * - .. figure:: /images/render_shader-nodes_textures_noise_solution2-constant-value.png

          Mitigating the issue by adding an arbitrary offset.

     - .. figure:: /images/render_shader-nodes_textures_noise_solution3-constant-value.png

          Mitigating the issue by evaluating at a higher dimension.

Similarly, in other configurations, one might experience some banding patterns in the noise,
where there are bands of high contrast areas followed by banding of low contrast areas.
For instance, planar surfaces that are slightly tilted along one of the axis
will have such a banding pattern.

.. figure:: /images/render_shader-nodes_textures_noise_issue-banding.png

   An example configuration where the noise have a banding pattern.

This happens because the slight tilt along one of the axis causes values along
the perpendicular axis to change very slowly making the grid structure of
the noise more apparent. The easiest way to mitigate this issue to rotate
the coordinates by an arbitrary amount.

.. figure:: /images/render_shader-nodes_textures_noise_solution-banding.png

   Mitigating the issue by rotating the coordinates by an arbitrary amount.
