pbox2d examples

Author: monkstone

samples/external_library/ruby_gem/jbox2d/distance_joint/boundary.rb

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+# The Nature of Code
+# Daniel Shiffman
+# http://natureofcode.com
+require 'forwardable'
+
+# A fixed boundary class
+class Boundary
+  extend Forwardable
+  def_delegators(:@app, :box2d, :rect_mode, :rect, :fill, :stroke)
+  # A boundary is a simple rectangle with x, y, width, and height
+  attr_reader :x, :y, :w, :h
+  
+  def initialize(x, y, w, h)
+    @x, @y, @w, @h = x, y, w, h
+    @app = $app
+    # Define the polygon
+    sd = PolygonShape.new
+    # Figure out the box2d coordinates
+    box2dW = box2d.scale_to_world(w / 2)
+    box2dH = box2d.scale_to_world(h / 2)
+    # We're just a box
+    sd.setAsBox(box2dW, box2dH)
+    # Create the body
+    bd = BodyDef.new
+    bd.type = BodyType::STATIC
+    bd.position.set(box2d.processing_to_world(x,y))
+    b = box2d.createBody(bd)
+    # Attached the shape to the body using a Fixture
+    b.createFixture(sd,1)
+  end
+
+  # Draw the boundary, if it were at an angle we'd have to do something fancier
+  def display
+    fill(0)
+    stroke(0)
+    rect_mode(Java::ProcessingCore::PConstants::CENTER)
+    rect(x, y, w, h)
+  end
+end

samples/external_library/ruby_gem/jbox2d/distance_joint/distance_joint.rb

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+# The Nature of Code
+# Daniel Shiffman
+# http://natureofcode.com
+
+# Example demonstrating distance joints 
+# A bridge is formed by connected a series of particles with joints
+
+require 'pbox2d'
+require_relative 'boundary'
+require_relative 'pair'
+require_relative 'particle'
+
+attr_reader :box2d, :boundaries, :pairs
+
+def setup
+  size(640, 360)
+  # Initialize box2d physics and create the world
+  @box2d = Box2D.new(self)
+  box2d.create_world
+  @pairs = []
+  @boundaries = []
+  # Add a bunch of fixed boundaries
+  boundaries << Boundary.new(width / 4, height - 5, width / 2 - 50, 10)
+  boundaries << Boundary.new(3 * width / 4, height - 50, width / 2 - 50, 10)
+end
+
+def draw
+  background(255)
+  pairs.each(&:display)
+  # Display all the boundaries
+  boundaries.each(&:display)
+  fill(0)
+  text('Click mouse to add connected particles.', 10, 20)
+end
+
+def mouse_pressed
+   pairs << Pair.new(mouse_x, mouse_y)
+end

samples/external_library/ruby_gem/jbox2d/distance_joint/pair.rb

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+# The Nature of Code
+# Daniel Shiffman
+# http://natureofcode.com
+require 'forwardable'
+
+# Series of Particles connected with distance joints
+class Pair
+  extend Forwardable
+  def_delegators(:@app, :box2d, :stroke, :line, :stroke_weight)
+  attr_reader :p1, :p2, :len
+  # Chain constructor
+  def initialize(x, y)
+    @app = $app
+    @len = 32
+    @p1 = Particle.new(x, y)
+    @p2 = Particle.new(x + rand(-1..1.0), y + rand(-1..1.0))
+    djd = DistanceJointDef.new
+    # Connection between previous particle and this one
+    djd.bodyA = p1.body
+    djd.bodyB = p2.body
+    # Equilibrium length
+    djd.length = box2d.scale_to_world(len)    
+    # These properties affect how springy the joint is 
+    djd.frequencyHz = 3     # Try a value less than 5 (0 for no elasticity)
+    djd.dampingRatio = 0.1  # Ranges between 0 and 1 (1 for no springiness)
+    # Make the joint.  Note we aren't storing a reference to the joint ourselves anywhere!
+    # We might need to someday, but for now it's ok
+    box2d.world.create_joint(djd)
+  end
+
+  def display
+    pos1 = box2d.body_coord(p1.body)
+    pos2 = box2d.body_coord(p2.body)
+    stroke(0)
+    stroke_weight(2)
+    line(pos1.x, pos1.y, pos2.x, pos2.y)
+    p1.display
+    p2.display
+  end
+end
+

samples/external_library/ruby_gem/jbox2d/distance_joint/particle.rb

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+# The Nature of Code
+# Daniel Shiffman
+# http://natureofcode.com
+require 'forwardable'
+
+# A circular particle
+class Particle
+  extend Forwardable
+  def_delegators(:@app, :fill, :stroke, :stroke_weight, :box2d, :height, :line,
+                 :push_matrix, :pop_matrix, :ellipse, :rotate, :translate)
+  # We need to keep track of a Body and a radius
+  attr_reader :body, :r
+  
+  def initialize(x, y)
+    @r = 8
+    @app = $app
+    # Define a body
+    bd = BodyDef.new
+    # Set its position
+    bd.position = box2d.processing_to_world(x,y)
+    bd.type = BodyType::DYNAMIC
+    @body = box2d.world.createBody(bd)
+
+    # Make the body's shape a circle
+    cs = CircleShape.new
+    cs.m_radius = box2d.scale_to_world(r)
+    
+    fd = FixtureDef.new
+    fd.shape = cs
+    # Parameters that affect physics
+    fd.density = 1
+    fd.friction = 0.01
+    fd.restitution = 0.3
+    
+    # Attach fixture to body
+    body.createFixture(fd)
+    body.setLinearVelocity(Vec2.new(rand(-5..5), rand(2..5)))
+  end
+
+  # This function removes the particle from the box2d world
+  def kill_body
+    box2d.destroy_body(body)
+  end
+  
+  # Is the particle ready for deletion?
+  def done
+    # Let's find the screen position of the particle
+    pos = box2d.body_coord(body)
+    # Is it off the bottom of the screen?
+    if pos.y > height + r * 2
+      kill_body
+      return true
+    end
+    false
+  end
+
+  def display
+    # We look at each body and get its screen position
+    pos = box2d.body_coord(body)
+    # Get its angle of rotation
+    a = body.get_angle
+    push_matrix
+    translate(pos.x, pos.y)
+    rotate(a)
+    fill(127)
+    stroke(0)
+    stroke_weight(2)
+    ellipse(0, 0, r * 2, r * 2)
+    # Let's add a line so we can see the rotation
+    line(0, 0, r, 0)
+    pop_matrix
+  end
+end
+
+

samples/external_library/ruby_gem/jbox2d/mouse_joint/boundary.rb

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+# The Nature of Code
+# Daniel Shiffman
+# http://natureofcode.com
+
+# A fixed boundary class (now incorporates angle)
+class Boundary
+  extend Forwardable
+  def_delegators(:@app, :fill, :no_fill, :stroke, :rect, :rect_mode, :box2d,
+                 :stroke_weight, :translate, :push_matrix, :pop_matrix, :rotate)
+  # A boundary is a simple rectangle with x,y,width,and height
+  attr_reader :x, :y, :w, :h, :b
+
+  def initialize(x, y, w, h, a)
+    @x, @y, @w, @h, @a = x, y, w, h, a
+    @app = $app
+    # Define the polygon
+    sd = PolygonShape.new
+    # Figure out the box2d coordinates
+    box2dw = box2d.scale_to_world(w / 2)
+    box2dh = box2d.scale_to_world(h / 2)
+    # We're just a box
+    sd.setAsBox(box2dw, box2dh)
+    # Create the body
+    bd = BodyDef.new
+    bd.type = BodyType::STATIC
+    bd.angle = a
+    bd.position.set(box2d.processing_to_world(x, y))
+    @b = box2d.create_body(bd)
+    # Attached the shape to the body using a Fixture
+    b.create_fixture(sd, 1)
+  end
+
+  # Draw the boundary, if it were at an angle we'd have to do something fancier
+  def display
+    no_fill
+    stroke(127)
+    fill(127)
+    stroke_weight(1)
+    rect_mode(Java::ProcessingCore::PConstants::CENTER)
+    a = b.get_angle
+    push_matrix
+    translate(x, y)
+    rotate(-a)
+    rect(0, 0, w, h)
+    pop_matrix
+  end
+end

samples/external_library/ruby_gem/jbox2d/mouse_joint/box.rb

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+# The Nature of Code
+# Daniel Shiffman
+# http://natureofcode.com
+
+# A rectangular box
+class Box
+  extend Forwardable
+  def_delegators(:@app, :fill, :stroke, :stroke_weight, :rect, :rect_mode,
+                 :box2d, :rotate, :translate, :push_matrix, :pop_matrix)
+  # We need to keep track of a Body and a width and height
+  attr_accessor :body, :w, :h
+  # Constructor
+  def initialize(x, y)
+    @app = $app
+    @w, @h = 24, 24
+    # Add the box to the box2d world
+    make_body(Vec2.new(x, y), w, h)
+  end
+
+  # This function removes the particle from the box2d world
+  def kill_body
+    box2d.destroy_body(body)
+  end
+
+  def contains(x, y)
+    world_point = box2d.processing_to_world(x, y)
+    f = body.get_fixture_list
+    f.test_point(world_point)
+  end
+
+  # Drawing the box
+  def display
+    # We look at each body and get its screen position
+    pos = box2d.body_coord(body)
+    # Get its angle of rotation
+    a = body.getAngle
+    rect_mode(Java::ProcessingCore::PConstants::CENTER)
+    push_matrix
+    translate(pos.x, pos.y)
+    rotate(a)
+    fill(127)
+    stroke(0)
+    stroke_weight(2)
+    rect(0, 0, w, h)
+    pop_matrix
+  end
+
+  # This function adds the rectangle to the box2d world
+  def make_body(center, w, h)
+    # Define and create the body
+    bd = BodyDef.new
+    bd.type = BodyType::DYNAMIC
+    bd.position.set(box2d.processing_to_world(center))
+    @body = box2d.createBody(bd)
+    # Define a polygon (this is what we use for a rectangle)
+    sd = PolygonShape.new
+    box2dw = box2d.scale_to_world(w / 2)
+    box2dh = box2d.scale_to_world(h / 2)
+    sd.setAsBox(box2dw, box2dh)
+    # Define a fixture
+    fd = FixtureDef.new
+    fd.shape = sd
+    # Parameters that affect physics
+    fd.density = 1
+    fd.friction = 0.3
+    fd.restitution = 0.5
+    body.create_fixture(fd)
+    # Give it some initial random velocity
+    body.set_linear_velocity(Vec2.new(rand(-5.0..5), rand(2.0..5)))
+    body.set_angular_velocity(rand(-5.0..5))
+  end
+end

samples/external_library/ruby_gem/jbox2d/mouse_joint/dummy_spring.rb

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+# The Nature of Code
+# Daniel Shiffman
+# http://natureofcode.com
+
+# This class avoids test for nil
+class DummySpring
+  def initialize; end
+
+  # If it exists we set its target to the mouse location
+  def update(_x, _y); end
+
+  def display; end
+
+  # This is the key function where
+  # we attach the spring to an x,y location
+  # and the Box object's location
+  def bind(x, y, box)
+    spring = Spring.new
+    spring.bind(x, y, box)
+    spring
+  end
+
+  def destroy; end
+end