Class: Pongo::WheelParticle

Inherits:
CircleParticle show all
Defined in:
lib/pongo/wheel_particle.rb

Overview

A particle that simulates the behavior of a wheel

Instance Attribute Summary collapse

Attributes inherited from CircleParticle

#radius

Attributes inherited from AbstractParticle

#center, #collidable, #collision, #curr, #first_collision, #fixed, #force_list, #forces, #friction, #interval, #inv_mass, #kfr, #mass, #multisample, #prev, #samp, #temp

Attributes inherited from AbstractItem

#always_repaint, #display_object, #display_object_offset, #display_object_rotation, #fill_alpha, #fill_color, #line_alpha, #line_color, #line_thickness, #renderer, #solid, #user_data, #visible

Instance Method Summary collapse

Methods inherited from CircleParticle

#interval_x, #interval_y, #projection

Methods inherited from AbstractParticle

#accumulate_forces, #add_force, #clear_forces, #collidable!, #collidable?, #components, #elasticity, #elasticity=, #fixed?, #position, #position=, #px, #px=, #py, #py=, #reset_first_collision!, #solid?, #test_particle_events, #velocity, #velocity=

Methods inherited from AbstractItem

#add_event_listener, #always_redraw!, #always_redraw=, #always_redraw?, #cleanup, #dispatch_event, #draw, #has_event_listener, #init, #set_fill, #set_line, #set_style, #visible!, #visible?

Constructor Details

#initialize(x, y, radius, options = {}) ⇒ WheelParticle

Returns a new instance of WheelParticle.



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# File 'lib/pongo/wheel_particle.rb', line 6

def initialize(x, y, radius, options={})
  options = {:fixed => false, :mass => 1, :elasticity => 0.3, :friction => 0, :traction => 1}.update(options)
  super(x, y, radius, options)
  @tan = Vector.new
  @norm_slip = Vector.new
  @rp = RimParticle.new(radius, 2)

  self.traction = options[:traction]
  @orientation = Vector.new
end

Instance Attribute Details

#norm_slip ⇒ Object

Returns the value of attribute norm_slip.



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# File 'lib/pongo/wheel_particle.rb', line 4

def norm_slip
  @norm_slip
end

#orientation ⇒ Object

Returns the value of attribute orientation.



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# File 'lib/pongo/wheel_particle.rb', line 4

def orientation
  @orientation
end

#rp ⇒ Object

Returns the value of attribute rp.



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# File 'lib/pongo/wheel_particle.rb', line 4

def rp
  @rp
end

#tan ⇒ Object

Returns the value of attribute tan.



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# File 'lib/pongo/wheel_particle.rb', line 4

def tan
  @tan
end

#traction ⇒ Object

The amount of traction during a collision. This property controls how much traction is applied when the WheelParticle is in contact with another particle. If the value is set to 0, there will be no traction and the WheelParticle will behave as if the surface was totally slippery, like ice. Values should be between 0 and 1.

<p> Note that the friction property behaves differently than traction. If the surface friction is set high during a collision, the WheelParticle will move slowly as if the surface was covered in glue. </p>



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# File 'lib/pongo/wheel_particle.rb', line 47

def traction
  @traction
end

Instance Method Details

#angle ⇒ Object 



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# File 'lib/pongo/wheel_particle.rb', line 60

def angle
  self.radian * MathUtil::ONE_EIGHTY_OVER_PI
end

#angular_velocity ⇒ Object

The angular velocity of the WheelParticle. You can alter this value to make the WheelParticle spin.



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# File 'lib/pongo/wheel_particle.rb', line 29

def angular_velocity
  @rp.angular_velocity
end

#angular_velocity=(a) ⇒ Object 



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# File 'lib/pongo/wheel_particle.rb', line 33

def angular_velocity=(a)
  @rp.angular_velocity = a
end

#radian ⇒ Object 



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# File 'lib/pongo/wheel_particle.rb', line 55

def radian
  @orientation.set_to(rp.curr)
  Math.atan2(@orientation.y, @orientation.x) + Math::PI
end

#resolve(n) ⇒ Object

simulates torque/wheel-ground interaction - n is the surface normal Origins of this code thanks to Raigan Burns, Metanet software



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# File 'lib/pongo/wheel_particle.rb', line 76

def resolve(n)
  # this is the tangent vector at the rim particle
  @tan.set_to(-@rp.curr.y, @rp.curr.x)

  # normalize so we can scale by the rotational speed
  @tan = @tan.normalize

  # velocity of the wheel's surface 
  wheel_surface_velocity = @tan * @rp.speed

  # the velocity of the wheel's surface relative to the ground
  combined_velocity = velocity.plus!(wheel_surface_velocity)

  # the wheel's comb velocity projected onto the contact normal
  cp = combined_velocity.cross(n)

  # set the wheel's spinspeed to track the ground
  @tan.mult!(cp)
  @rp.prev.copy(@rp.curr - @tan)

  # some of the wheel's torque is removed and converted into linear displacement
  slip_speed = (1 - @traction) * @rp.speed
  norm_slip.set_to(slip_speed * n.y, slip_speed * n.x)
  @curr.plus!(norm_slip)
  @rp.speed *= @traction
end

#resolve_collision(mtd, vel, n, d, o, p) ⇒ Object 



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# File 'lib/pongo/wheel_particle.rb', line 69

def resolve_collision(mtd, vel, n, d, o, p)
  super
  resolve(n * MathUtil.sign(d * o))
end

#speed ⇒ Object

The speed of the WheelParticle. You can alter this value to make the WheelParticle spin.



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# File 'lib/pongo/wheel_particle.rb', line 19

def speed
  @rp.speed
end

#speed=(s) ⇒ Object 



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# File 'lib/pongo/wheel_particle.rb', line 23

def speed=(s)
  @rp.speed = s
end

#update(dt) ⇒ Object 



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# File 'lib/pongo/wheel_particle.rb', line 64

def update(dt)
  super
  @rp.update(dt)
end