How to generate a random convex polygon?

Question

I\'m trying to devise a method for generating random 2D convex polygons. It has to have the following properties:

• coordinates should be integers;
• the poly

Answer 1

I've made the ruby port as well thanks to both @Mangara's answer and @Azat's answer:

#!/usr/bin/env ruby
# frozen_string_literal: true

module ValtrAlgorithm
  module_function def random_polygon(length)
    raise ArgumentError, "length should be > 2" unless length > 2

    min_x, *xs, max_x = Array.new(length) { rand }.sort
    min_y, *ys, max_y = Array.new(length) { rand }.sort
    # Divide the interior points into two chains and
    # extract the vector components.
    vec_xs = to_random_vectors(xs, min_x, max_x)
    vec_ys = to_random_vectors(ys, min_y, max_y).
      # Randomly pair up the X- and Y-components
      shuffle
    # Combine the paired up components into vectors
    vecs = vec_xs.zip(vec_ys).
      # Sort the vectors by angle, in a counter clockwise fashion. Remove the
      # `-` to make it clockwise.
      sort_by { |x, y| - Math.atan2(y, x) }

    # Lay them end-to-end
    point_x = point_y = 0
    min_polygon_x = min_polygon_y = 0
    points = []
    vecs.each do |vec_x, vec_y|
      points.append([vec_x, vec_y])
      point_x += vec_x
      point_y += vec_y
      min_polygon_x = [min_polygon_x, point_x].min
      min_polygon_y = [min_polygon_y, point_y].min
    end
    shift_x = min_x - min_polygon_x
    shift_y = min_y - min_polygon_y
    result = points.map { |point_x, point_y| [point_x + shift_x, point_y + shift_y] }
    # Append first point to make it a valid linear ring
    result << result.first
  end

  private def to_random_vectors(coordinates, min, max)
    last_min = last_max = min
    ary = []
    coordinates.each do |coordinate|
      if rand > 0.5
        ary << coordinate - last_min
        last_min = coordinate
      else
        ary << last_max - coordinate
        last_max = coordinate
      end
    end
    ary << max - last_min << last_max - max
  end
end