Gosu + Chipmunk で遊ぶ（Ruby）

物理エンジン Chipmunk + Gosu でごく簡単なドミノ倒しみたいな動画を作ってみました。Ruby 2.3.3, Linux Mint 18.3 で確認しました。

gosu_chipmunk_sample3.rb

require 'gosu'
require 'rmagick'
require 'chipmunk'

CV = CP::Vec2

Width, Height = 500, 200
Wall_h = 50
BOD_w, BOD_h = 20, 100

class MyWindow < Gosu::Window
  def initialize
    super Width, Height, false
    self.caption = "Gosu + Chipmunk"
    
    @space = CP::Space.new
    @space.iterations = 3
    @space.gravity = CV.new(0, 100)
    
    background = Magick::Image.new(Width, Height) {self.background_color = "snow"}
    
    #地面
    gc = Magick::Draw.new
    gc.fill('firebrick')
    gc.rectangle(0, Height - Wall_h, Width, Height)
    gc.draw(background)
    
    #板
    board_image = Magick::Image.new(BOD_w, BOD_h)
    gc = Magick::Draw.new
    gc.fill('lightgreen')
    gc.rectangle(0, 0, BOD_w, BOD_h)
    gc.draw(board_image)
    @board = Gosu::Image.new(board_image)
    
    #円
    circle_image = Magick::Image.new(11, 11) {self.background_color = 'transparent'}
    gc = Magick::Draw.new
    gc.fill('skyblue')
    gc.circle(5, 5, 0, 5)
    gc.draw(circle_image)
    @circle = Gosu::Image.new(circle_image)
    
    #chipmunk
    #地面
    sb = CP::Body.new_static
    x1, y1 = 0, Height - Wall_h
    x2, y2 = Width, Height
    verts = [CV.new(x1, y1), CV.new(x1, y2), CV.new(x2, y2), CV.new(x2, y1)]
    wshape = CP::Shape::Poly.new(sb, verts, CV.new(0, 0))
    wshape.e = 1
    wshape.u = 1
    @space.add_shape(wshape)
    
    #板
    set_boards(5)
    
    #円
    @bodyc = CP::Body.new(7, CP::INFINITY)
    @bodyc.p = CV.new(0, 20)
    @bodyc.v = CV.new(50, 0)
    shape = CP::Shape::Circle.new(@bodyc, 5, CV.new(0, 0))
    shape.e = 0.8
    shape.u = 0
    @space.add_body(@bodyc)
    @space.add_shape(shape)
    
    @background_image = Gosu::Image.new(background)
  end
  
  def set_boards(n)
    @boards = []
    n.times do |i|
      x, y = BOD_w / 2.0, BOD_h / 2.0
      bx = [CV.new(-x, -y), CV.new(-x, y), CV.new(x, y), CV.new(x, -y)]
      body = CP::Body.new(10, CP.moment_for_poly(10, bx, CV.new(0, 0)))
      body.p = CV.new(50 + 80 * i, Height - Wall_h - y)
      shape = CP::Shape::Poly.new(body, bx, CV.new(0, 0))
      shape.e = 0
      shape.u = 1
      @space.add_body(body)
      @space.add_shape(shape)
      
      @boards << body
    end
  end
  
  def update
    @space.step(1.0 / 60)
  end
  
  def draw
    @background_image.draw(0, 0, 0)
    @boards.each do |b|
      @board.draw_rot(b.p.x, b.p.y, 2, (b.a - Math::PI / 2).radians_to_gosu)
    end
    @circle.draw_rot(@bodyc.p.x, @bodyc.p.y, 1, 0)
  end
end

MyWindow.new.show

パラメータの調節がむずかしかったですね。それぞれの質量の値は重要です。長方形はあんまり軽すぎると不安定になったりします。