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Contents
# The Nature of Code
# Daniel Shiffman
# http://natureofcode.com
# Series of Particles connected with distance joints
class Pair
extend Forwardable
def_delegators(:@app, :box2d, :stroke, :line, :stroke_weight)
attr_reader :p1, :p2, :len, :joint
# 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.
@joint = box2d.world.create_joint(djd)
end
def kill_bodies
box2d.world.destroy_joint(joint)
@joint = nil
box2d.destroy_body(p1.body)
box2d.destroy_body(p2.body)
end
# Is the pair ready for deletion?
def done?
# Let's find the screen position of the particle
pos1 = box2d.body_coord(p1.body)
pos2 = box2d.body_coord(p2.body)
# Is it off the screen?
if (0..@app.width).include?(pos1.x) || (0..@app.width).include?(pos2.x)
if (0..@app.height).include?(pos1.y) || (0..@app.height).include?(pos2.y)
return false
end
end
kill_bodies
true
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
Version data entries
9 entries across 9 versions & 1 rubygems