Procedurally generated background

tree.rb

require 'victor'
require 'rgb'

WIDTH=3840
HEIGHT=2160

prng = Random.new

RING_RAD = prng.rand(30..80)
ANGLE_SPREAD=Random.new.rand(3..10)

HUE_STEP = 0.5 / ( WIDTH / RING_RAD)

svg = Victor::SVG.new width: WIDTH, height: HEIGHT, style: { background: '#111' }

Seed = Struct.new :angle, :x, :y

start_hue = prng.rand(0.0..1.0)

color = RGB::Color.from_fractions(start_hue,1.0,0.7)

svg.build do
  rect x: 0, y: 0, width: WIDTH, height: HEIGHT, fill: '#111'

  css['.rings'] = {
    stroke: color.to_rgb_hex, 
         stroke_width: 1,
         "fill-opacity": 0.0
  }
  circle cx: WIDTH/2, cy: HEIGHT/2, r: 2, fill: '#FFF'


  seeds = (1..3).map do |i|
    prng.rand(0...360)
  end.map do |angle|
    rad = 2.0 * Math::PI * angle / 360.0
    x = WIDTH/2 + RING_RAD * Math.cos(rad) 
    y = HEIGHT/2 + RING_RAD * Math.sin(rad) 
    Seed.new angle, x, y
  end

  seeds.each do |seed|
    path d: ['M', WIDTH/2, HEIGHT/2, 'L', seed.x, seed.y ], stroke: color.to_rgb_hex, stroke_width: 1
  end

  hue = start_hue

  RING_RAD.step([WIDTH,HEIGHT].max, RING_RAD) do |r|
    hue = ( hue + HUE_STEP ) % 1.0
    color = RGB::Color.from_fractions(hue,1.0,0.7)
    circle cx: WIDTH/2, cy: HEIGHT/2, r: r, class: 'rings', stroke: color.to_rgb_hex
    last_seeds = seeds
    seeds = Array.new
    last_seeds.each do |seed|
      (1..(prng.rand(1..3))).map do |i|
        prng.rand((seed.angle-ANGLE_SPREAD)..(seed.angle+ANGLE_SPREAD))
      end.map do |angle|
        rad = 2.0 * Math::PI * angle / 360.0
        x = WIDTH/2 + r * Math.cos(rad)
        y = HEIGHT/2 + r * Math.sin(rad)
        Seed.new angle, x, y
      end.each do |next_seed|
        path d: ['M', seed.x, seed.y, 'L', next_seed.x, next_seed.y ], stroke: color.to_rgb_hex, stroke_width: 1

        seeds << next_seed
      end
    end
    seeds = seeds.uniq
  end
end

svg.save 'tree'