Box2D Forums

require 'mkmf'
create_makefile('RubyBox2d')

...
pos: 0.0,1.25000035762787 rot: 0.0
pos: 0.0,1.12500035762787 rot: 0.0
pos: 0.0,0.997222602367401 rot: 0.0
pos: -4.35693873441778e-05,0.997230529785156 rot: 4.35693873441778e-05
pos: -3.40081496688072e-05,0.997228801250458 rot: 3.40077458531596e-05
...

require 'rubygems'

require 'gosu'
require 'box2d'

include Box2d

class GameWindow < Gosu::Window
   RadToDeg = 57.295779513082323

   def initialize
    super(640,480, false, 20)
    self.caption = "Box2d Demo"

      # Pointer ist 28x38, Hotspot 6,1
      @pointer = Gosu::Image.new(self, "media/img/pointer.png", true)

      @stone = Gosu::Image.new(self, "media/img/stone.png", false)

      @info = Gosu::Font.new(self, "arial", 12)
      b = B2AABB.new
      b.minVertex.set(0.0, 0.0)
      b.maxVertex.set(640.0, 480.0)
      gravity = B2Vec2.new(0.0, 180.0)
      do_sleep = true
      @w = B2World.new(b,gravity,do_sleep)

      
      groundBoxDef = B2BoxDef.new
      groundBoxDef.extents.set(320.0, 5.0)
      groundBoxDef.density = 0.0

      groundBodyDef = B2BodyDef.new
      groundBodyDef.position.set(320.0, 460.0)
      groundBodyDef.add_shape(groundBoxDef)

      @walls = []
      
      bd = create_wall(320.0,5.0,320.0,460.0)
      @walls <<  {:body => @w.create_body(bd), :shape => [320.0,5.0]};
      bd = create_wall(5.0,130.0,5.0,325.0)
      @walls <<  {:body => @w.create_body(bd), :shape => [5.0,130.0]};
      bd = create_wall(5.0,130.0,635,325.0)
      @walls <<  {:body => @w.create_body(bd), :shape => [5.0,130.0]};

      bd = create_box(20.0,20.0,320.0,40.0,0.6)
      
      @entities = []
      @entities <<  {:body => @w.create_body(bd), :shape => [20.0,20.0]};

      @last_time = Gosu::milliseconds()
  end

   def create_box(w,h,x,y,rot)
      boxDef = B2BoxDef.new
      boxDef.extents.set(w,h)
      boxDef.density = 0.1
      boxDef.friction = 1.3
      boxDef.restitution = 0.5
      
      bodyDef = B2BodyDef.new
      bodyDef.position.set(x,y)
      bodyDef.rotation = rot
      bodyDef.allowSleep = true;
      bodyDef.add_shape(boxDef);
      bodyDef.userData = ["box",10.0,10.0]
      return bodyDef;
   end

   def create_wall(w,h,x,y)
      boxDef = B2BoxDef.new
      boxDef.extents.set(w,h)
      boxDef.density = 0.0
      bodyDef = B2BodyDef.new
      bodyDef.position.set(x,y)
      bodyDef.allowSleep = true;
      bodyDef.add_shape(boxDef);
      bodyDef.userData = ["wall",10.0,10.0]
      return bodyDef;
   end

def button_down(id)
    if id == Gosu::Button::MsRight then
         bd = create_box(20.0,20.0,self.mouse_x, self.mouse_y,0.0)
         @entities << {:body => @w.create_body(bd), :shape => [20.0,20.0]};
      end
      
   end

  def update
  end

  def draw
      #c = Gosu::Color.new(255,0,0,255)
      c = Gosu::Color.new(255,255,255,255)
      c1 = Gosu::Color.new(167,167,167,167)

      #time_step = (Gosu::milliseconds() - @last_time) / 1000.0
      time_step = 1.0 / 60
      @last_time = Gosu::milliseconds()

      iterations = 10
      @w.step(time_step, iterations)
      @entities.each{|e|
         pos = e[:body].get_origin_position()
         rot = e[:body].get_rotation()
         self.draw_stone(pos.x - e[:shape][0],pos.y - e[:shape][1], e[:shape][0] * 2, e[:shape][1] * 2,rot,c)
      }
      
      @walls.each{|w|
         pos = w[:body].get_origin_position()
         rot = w[:body].get_rotation()
         self.draw_rectangle(pos.x - w[:shape][0],pos.y - w[:shape][1], w[:shape][0] * 2, w[:shape][1] * 2,rot,c1)
      }
      
      @info.draw("x: #{mouse_x} y: #{mouse_y} ms: #{time_step}",10,10,0)
      @pointer.draw(self.mouse_x-6, self.mouse_y-1,0)

   end

   def draw_stone(x, y, w, h, rot,c)
      if rot == 0.0
         lt = [ x, y ]
         lb = [ lt[0], lt[1] + h ]
         rb = [ lt[0] + w, lt[1] + h ]
         rt = [ lt[0] + w, lt[1] ]
         @stone.draw_as_quad(lt[0], lt[1], c, lb[0], lb[1], c, rt[0], rt[1], c, rb[0], rb[1], c,-1.0)
      else
         pos = [x+(w/2.0),y+(h/2.0)]
         lt = move(rotate([-w/2.0,-h/2.0], rot), pos)
         lb = move(rotate([-w/2.0,h/2.0], rot), pos)
         rb = move(rotate([w/2.0,h/2.0], rot), pos)
         rt = move(rotate([w/2.0,-h/2.0], rot), pos)
         @stone.draw_as_quad(lt[0], lt[1], c, lb[0], lb[1], c, rt[0], rt[1], c, rb[0], rb[1], c,-1.0)
      end
   end


   def draw_rectangle(x, y, w, h, rot, c)
      if rot == 0.0
         lt = [ x, y ]
         lb = [ lt[0], lt[1] + h ]
         rb = [ lt[0] + w, lt[1] + h ]
         rt = [ lt[0] + w, lt[1] ]
         self.draw_quad(lt[0], lt[1], c, lb[0], lb[1], c, rt[0], rt[1], c, rb[0], rb[1], c)
      else
         pos = [x+(w/2.0),y+(h/2.0)]
         lt = move(rotate([-w/2.0,-h/2.0], rot), pos)
         lb = move(rotate([-w/2.0,h/2.0], rot), pos)
         rb = move(rotate([w/2.0,h/2.0], rot), pos)
         rt = move(rotate([w/2.0,-h/2.0], rot), pos)
         self.draw_quad(lt[0], lt[1], c, lb[0], lb[1], c, rt[0], rt[1], c, rb[0], rb[1], c)
      end
   end

   def move(p,pos)
      return [p[0] + pos[0], p[1] + pos[1]]
   end
   
   def rotate(p, theta)
      # x' = cos(theta)*x - sin(theta)*y
      # y' = sin(theta)*x + cos(theta)*y
      ct = Math.cos(theta)
      cs = Math.sin(theta)
      return [ct *p[0] - cs *p[1],cs*p[0] + ct*p[1]]
   end
end


window = GameWindow.new
window.show