Class: Perlin::Noise

Inherits:
Object
  • Object
show all
Defined in:
lib/perlin/noise.rb

Constant Summary collapse

DEFAULT_OPTIONS = 
{
  :interval => 256,
  :curve => Perlin::Curve::QUINTIC,
  :seed => nil
}

Instance Method Summary collapse

Constructor Details

#initialize(dim, options = {}) ⇒ Noise

Returns a new instance of Noise.

Raises:

  • (ArgumentError) 


9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
 
# File 'lib/perlin/noise.rb', line 9

def initialize dim, options = {}
  options = DEFAULT_OPTIONS.merge options

  @dim = dim
  @interval = options.fetch(:interval)
  @curve = options.fetch(:curve)
  @seed = options.fetch(:seed)

  raise ArgumentError.new("Invalid dimension: must be a positive integer")  unless @dim.is_a?(Fixnum) && @dim > 0
  raise ArgumentError.new("Invalid interval: must be a positive integer")   unless @interval.is_a?(Fixnum) && @interval > 0
  raise ArgumentError.new("Invalid curve specified: must be a Proc object") unless @curve.is_a?(Proc)
  raise ArgumentError.new("Invalid seed: must be a number")                 unless @seed.nil? || @seed.is_a?(Numeric)

  # Generate pseudo-random gradient vector for each grid point
  @gradient_table = Perlin::GradientTable.new @dim, @interval, @seed
end

Instance Method Details

#[](*coords) ⇒ Float

Returns Noise value between (-1..1).

Parameters:

  • Coordinates (*coords)

Returns:

  • (Float) —

    Noise value between (-1..1)

Raises:

  • (ArgumentError) 


28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
 
# File 'lib/perlin/noise.rb', line 28

def [] *coords
  raise ArgumentError.new("Invalid coordinates") unless coords.length == @dim

  coords = Vector[*coords]
  cell = Vector[*coords.map(&:to_i)]
  diff = coords - cell

  # Calculate noise factor at each surrouning vertex
  nf = {}
  iterate @dim, 2 do |idx|
    idx = Vector[*idx]

    # "The value of each gradient ramp is computed by means of a scalar
    # product (dot product) between the gradient vectors of each grid point
    # and the vectors from the grid points."
    gv = @gradient_table[ * (cell + idx).to_a ]
    nf[idx.to_a] = gv.inner_product(diff - idx)
  end

  dim = @dim
  diff.to_a.each do |u|
    bu = @curve.call u

    # Pair-wise interpolation, trimming down dimensions
    iterate dim, 2 do |idx1|
      next if idx1.first == 1

      idx2 = idx1.dup
      idx2[0] = 1
      idx3 = idx1[1..-1]

      nf[idx3] = nf[idx1] + bu * (nf[idx2] - nf[idx1])
    end
    dim -= 1
  end
  (nf[[]] + 1) * 0.5
end