add blobby example

Author: monkstone

examples/blobby/blob.rb

@@ -0,0 +1,93 @@
+# The Nature of Code
+# <http://www.shiffman.net/teaching/nature>
+# Spring 2012
+# Box2DProcessing example
+
+# A blob skeleton
+# Could be used to create blobbly characters a la Nokia Friends
+# http://postspectacular.com/work/nokia/friends/start
+
+class Blob
+  include Processing::Proxy
+  # A list to keep track of all the points in our blob
+  attr_reader :skeleton, :body_radius, :radius, :total_points
+  # We should modify this constructor to receive arguments
+  # So that we can make many different types of blobs
+  
+  def initialize
+    # Create the empty 
+    @skeleton = []
+    # Let's make a volume of joints!
+    cvjd = ConstantVolumeJointDef.new
+    # Where and how big is the blob
+    center = Vec2.new(width / 2, height / 2)
+    @radius = 100
+    @total_points = 20
+    @body_radius = 12
+    # Initialize all the points
+    total_points.times do |i|
+      # Look polar to cartesian coordinate transformation!
+      theta = map1d(i, 0..total_points, 0..TWO_PI)
+      x = center.x + radius * sin(theta)
+      y = center.y + radius * cos(theta)
+      # Make each individual body
+      bd = BodyDef.new
+      bd.type = BodyType::DYNAMIC
+      bd.fixedRotation = true # no rotation!
+      bd.position.set(box2d.processing_to_world(Vec2.new(x, y)))
+      body = box2d.createBody(bd)
+      # The body is a circle
+      cs = CircleShape.new
+      cs.m_radius = box2d.scale_to_world(body_radius)
+      # Define a fixture
+      fd = FixtureDef.new
+      fd.shape = cs
+      # For filtering out collisions
+      #fd.filter.groupIndex = -2
+      # Parameters that affect physics
+      fd.density = 1
+      # Finalize the body
+      body.create_fixture(fd)
+      # Add it to the volume
+      cvjd.add_body(body)
+      # Store our own copy for later rendering
+      skeleton << body
+   end
+    # These parameters control how stiff vs. jiggly the blob is
+    cvjd.frequencyHz = 10.0
+    cvjd.dampingRatio = 1.0
+    # Put the joint thing in our world!
+    box2d.world.create_joint(cvjd)
+ end
+ 
+  # Time to draw the blob!
+  # Can you make it a cute character, a la 
+  # http://postspectacular.com/work/nokia/friends/start
+  def display
+    # Draw the outline
+    begin_shape
+    no_fill
+    stroke(0)
+    stroke_weight(1)
+    skeleton.each do |b|
+      pos = box2d.body_coord(b)
+      vertex(pos.x, pos.y)
+    end
+    end_shape(CLOSE)
+    # Draw the individual circles
+    skeleton.each do |b|
+      # We look at each body and get its screen position
+      pos = box2d.body_coord(b)
+      # Get its angle of rotation
+      a = b.get_angle
+      push_matrix
+      translate(pos.x, pos.y)
+      rotate(a)
+      fill(175)
+      stroke(0)
+      stroke_weight(1)
+      ellipse(0, 0, body_radius * 2, body_radius * 2)
+      pop_matrix
+   end
+ end
+end

examples/blobby/blobby.rb

@@ -0,0 +1,43 @@
+# The Nature of Code
+# <http:#www.shiffman.net/teaching/nature>
+# Spring 2012
+# Box2DProcessing example
+
+# A blob skeleton
+# Could be used to create blobbly characters a la Nokia Friends
+# http://postspectacular.com/work/nokia/friends/start
+
+# This seems to be broken with the Box2D 2.1.2 version I'm using
+
+require 'pbox2d'
+require 'forwardable'
+require_relative 'boundary'
+require_relative 'blob'
+
+attr_reader :boundaries, :blob, :box2d
+
+def settings
+  size(400, 300)
+end
+
+def setup
+  sketch_title 'Blobby'  
+  # Initialize box2d physics and create the world
+  @box2d = WorldBuilder.build(app: self, gravity: [0, -20])
+  box2d.create_world
+  @boundaries = []
+  boundaries << Boundary.new(box2d, Vec2D.new(width / 2, height - 5), Vec2D.new(width, 10))
+  boundaries << Boundary.new(box2d, Vec2D.new(width / 2, 5), Vec2D.new(width, 10))
+  boundaries << Boundary.new(box2d, Vec2D.new(width - 5, height / 2), Vec2D.new(10, height))
+  boundaries << Boundary.new(box2d, Vec2D.new(5, height / 2), Vec2D.new(10, height))
+  # Make a new blob
+  @blob = Blob.new
+end
+
+def draw
+  background(255)
+  # We must always step through time!
+  boundaries.each(&:display)
+  # Show the blob!
+  blob.display
+end

examples/blobby/boundary.rb

@@ -0,0 +1,37 @@
+class Boundary
+  include Processing::Proxy
+  attr_reader :box2d, :b, :pos, :size, :a
+
+  def initialize(b2d, pos, sz, a = 0)
+    @box2d, @pos, @size, @a = b2d, pos, sz, a
+    # Define the polygon
+    sd = PolygonShape.new
+    # Figure out the box2d coordinates
+    box2d_w = box2d.scale_to_world(size.x / 2)
+    box2d_h = box2d.scale_to_world(size.y / 2)
+    # We're just a box
+    sd.set_as_box(box2d_w, box2d_h)
+    # Create the body
+    bd = BodyDef.new
+    bd.type = BodyType::STATIC
+    bd.angle = a
+    bd.position.set(box2d.processing_to_world(pos.x, pos.y))
+    @b = box2d.create_body(bd)
+    # Attached the shape to the body using a Fixture
+    b.create_fixture(sd, 1)
+  end
+
+  # Draw the boundary, it doesn't move so we don't have to ask the Body for location
+  def display
+    fill(0)
+    stroke(0)
+    stroke_weight(1)
+    rect_mode(CENTER)
+    a = b.get_angle
+    push_matrix
+    translate(pos.x, pos.y)
+    rotate(-a)
+    rect(0, 0, size.x,size.y)
+    pop_matrix
+  end
+end

lib/pbox2d.rb

@@ -27,6 +27,7 @@ def import_class_list(list, string)
   RevoluteJoint
   RevoluteJointDef
   MouseJointDef
+  ConstantVolumeJointDef
 )
 joint_format = 'org.jbox2d.dynamics.joints.%s'
 import_class_list(joint, joint_format)