bezier.rb

#!/usr/bin/env ruby
require './lib/render'

class Vector
  def lerp(*); self end
end

class Array
  def lerp(t)
    first.lerp(t) * (1.0 - t) + last.lerp(t) * t
  end

  def to_bezier
    size == 2 ? self :
    each_index.map do |index|
      [self[index], self[index + 1]]
    end[0...-1].to_bezier
  end
end

def make_lerp_path(tuple, steps)
  Array.new(steps) { |index| tuple.lerp(index.to_f / (steps - 1)) }
end

p [0, 1].to_bezier # [0, 1]
p [0, 1, 2].to_bezier # [[0, 1], [1, 2]]
p [0, 1, 2, 3].to_bezier # [[[0, 1], [1, 2]], [[1, 2], [2, 3]]]

objects = []
# through points https://stackoverflow.com/questions/6711707/draw-a-quadratic-b%C3%A9zier-curve-through-three-given-points
# connect curves https://www.scratchapixel.com/lessons/advanced-rendering/bezier-curve-rendering-utah-teapot
points = [Vector[10, 10], Vector[210, 50], Vector[150, 250], Vector[400, 10]]
bezier = points.to_bezier

objects << Render.grey(points)
objects += points.map { |p| Render.white p }

curve = make_lerp_path(bezier, 30)
objects << Render.green(curve)

renderer = Render.new title: 'Bezier curve'
renderer.scene = { objects: objects, types: {
  Vector => { circle: ->(v) { v } }, Array => { path: ->(a) { a } }
} }

# renderer.scene[:types][MyObject] = proc do |r, o|
#  r.color :red
#  r.point o.position
#  r.path o.path
# end

renderer.run