This function generates either 2 or 3 dimensional perlin noise, with optional
pertubation and fractality. Perlin noise is one of the most well known
gradient noise algorithms and have been used extensively as the basis for
generating landscapes and textures, as well as within generative art.
The algorithm was developed by Ken Perlin in 1983.

```
noise_perlin(
dim,
frequency = 0.01,
interpolator = "quintic",
fractal = "fbm",
octaves = 3,
lacunarity = 2,
gain = 0.5,
pertubation = "none",
pertubation_amplitude = 1
)
gen_perlin(
x,
y = NULL,
z = NULL,
frequency = 1,
seed = NULL,
interpolator = "quintic",
...
)
```

## Arguments

- dim
The dimensions (height, width, (and depth)) of the noise to be
generated. The length determines the dimensionality of the noise.

- frequency
Determines the granularity of the features in the noise.

- interpolator
How should values between sampled points be calculated?
Either `'linear'`

, `'hermite'`

, or `'quintic'`

(default), ranging from lowest
to highest quality.

- fractal
The fractal type to use. Either `'none'`

, `'fbm'`

(default),
`'billow'`

, or `'rigid-multi'`

. It is suggested that you experiment with the
different types to get a feel for how they behaves.

- octaves
The number of noise layers used to create the fractal noise.
Ignored if `fractal = 'none'`

. Defaults to `3`

.

- lacunarity
The frequency multiplier between successive noise layers
when building fractal noise. Ignored if `fractal = 'none'`

. Defaults to `2`

.

- gain
The relative strength between successive noise layers when
building fractal noise. Ignored if `fractal = 'none'`

. Defaults to `0.5`

.

- pertubation
The pertubation to use. Either `'none'`

(default),
`'normal'`

, or `'fractal'`

. Defines the displacement (warping) of the noise,
with `'normal'`

giving a smooth warping and `'fractal'`

giving a more eratic
warping.

- pertubation_amplitude
The maximal pertubation distance from the
origin. Ignored if `pertubation = 'none'`

. Defaults to `1`

.

- x, y, z
Coordinates to get noise value from

- seed
The seed to use for the noise. If `NULL`

a random seed will be
used

- ...
ignored

## Value

For `noise_perlin()`

a matrix if `length(dim) == 2`

or an array if
`length(dim) == 3`

. For `gen_perlin()`

a numeric vector matching the length of
the input.

## References

Perlin, Ken (1985). *An Image Synthesizer*. SIGGRAPH Comput. Graph. 19
(0097-8930): 287–296. doi:10.1145/325165.325247.

## Examples

```
# Basic use
noise <- noise_perlin(c(100, 100))
plot(as.raster(normalise(noise)))
# Using the generator
grid <- long_grid(seq(1, 10, length.out = 1000), seq(1, 10, length.out = 1000))
grid$noise <- gen_perlin(grid$x, grid$y)
plot(grid, noise)
```