Class: Pongo::SpringConstraintParticle

Inherits:
RectangleParticle show all
Defined in:
lib/pongo/spring_constraint_particle.rb

Instance Attribute Summary collapse

Attributes inherited from RectangleParticle

#axes, #extents, #radian

Attributes inherited from AbstractParticle

#center, #collidable, #collision, #curr, #first_collision, #force_list, #forces, #interval, #kfr, #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 RectangleParticle

#angle, #angle=, #height, #height=, #projection, #set_axes, #width, #width=

Methods inherited from AbstractParticle

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

Methods inherited from AbstractItem

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

Constructor Details

#initialize(p1, p2, p, rect_height, rect_scale, scale_to_length) ⇒ SpringConstraintParticle

Returns a new instance of SpringConstraintParticle.



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# File 'lib/pongo/spring_constraint_particle.rb', line 10

def initialize(p1, p2, p, rect_height, rect_scale, scale_to_length)
  super(0.0, 0.0, 0.0, 0.0, :fixed => false)

  @p1 = p1
  @p2 = p2

  self.lamda = Vector.new
  self.avg_velocity = Vector.new

  @parent = p
  @rect_scale = rect_scale
  @rect_height = rect_height
  @scale_to_length = scale_to_length

  @fixed_end_limit = 0.0
  @rca = Vector.new
  @rcb = Vector.new
end

Instance Attribute Details

#avg_velocity ⇒ Object

Returns the value of attribute avg_velocity.



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# File 'lib/pongo/spring_constraint_particle.rb', line 8

def avg_velocity
  @avg_velocity
end

#fixed_end_limit ⇒ Object

Returns the value of attribute fixed_end_limit.



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# File 'lib/pongo/spring_constraint_particle.rb', line 8

def fixed_end_limit
  @fixed_end_limit
end

#lamda ⇒ Object

Returns the value of attribute lamda.



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# File 'lib/pongo/spring_constraint_particle.rb', line 8

def lamda
  @lamda
end

#p1 ⇒ Object

Returns the value of attribute p1.



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# File 'lib/pongo/spring_constraint_particle.rb', line 8

def p1
  @p1
end

#p2 ⇒ Object

Returns the value of attribute p2.



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# File 'lib/pongo/spring_constraint_particle.rb', line 8

def p2
  @p2
end

#parent ⇒ Object

Returns the value of attribute parent.



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# File 'lib/pongo/spring_constraint_particle.rb', line 8

def parent
  @parent
end

#rca ⇒ Object

Returns the value of attribute rca.



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# File 'lib/pongo/spring_constraint_particle.rb', line 8

def rca
  @rca
end

#rcb ⇒ Object

Returns the value of attribute rcb.



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# File 'lib/pongo/spring_constraint_particle.rb', line 8

def rcb
  @rcb
end

#rect_height ⇒ Object

Returns the value of attribute rect_height.



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# File 'lib/pongo/spring_constraint_particle.rb', line 8

def rect_height
  @rect_height
end

#rect_scale ⇒ Object

Returns the value of attribute rect_scale.



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# File 'lib/pongo/spring_constraint_particle.rb', line 8

def rect_scale
  @rect_scale
end

#s ⇒ Object

Returns the value of attribute s.



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# File 'lib/pongo/spring_constraint_particle.rb', line 8

def s
  @s
end

#scale_to_length ⇒ Object

Returns the value of attribute scale_to_length.



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# File 'lib/pongo/spring_constraint_particle.rb', line 8

def scale_to_length
  @scale_to_length
end

Instance Method Details

#closest_param_point(c) ⇒ Object

given point c, returns a parameterized location on this SCP. Note this is just treating the SCP as if it were a line segment (ab).



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# File 'lib/pongo/spring_constraint_particle.rb', line 127

def closest_param_point(c)
  ab = @p2.curr - @p1.curr
  t = (ab.dot(c - @p1.curr)) / (ab.dot(ab))
  MathUtil.clamp(t, 0.0, 1.0)
end

#closest_pt_segment_segment ⇒ Object

pp1-pq1 will be the SCP line segment on which we need parameterized s.



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# File 'lib/pongo/spring_constraint_particle.rb', line 204

def closest_pt_segment_segment
  pp1 = @p1.curr
  pq1 = @p2.curr
  pp2 = @rca
  pq2 = @rcb

  d1 = pq1 - pp1
  d2 = pq2 - pp2
  r = pp1 - pp2

  a = d1.dot(d1)
  e = d2.dot(d2)
  f = d2.dot(r)

  c = d1.dot(r)
  b = d1.dot(d2)
  denom = a * e - b * b

  s = denom != 0.0 ? MathUtil.clamp((b * f - c * e) / denom, 0.0, 1.0) : 0.5
  t = (b * s + f) / e

  t, s = t < 0 \
    ? [0.0, MathUtil.clamp(-c / a, 0.0, 1.0)] \
    : [1.0, MathUtil.clamp((b - c) / a, 0.0, 1.0)]

  c1 = pp1 + (d1 * s)
  c2 = pp2 + (d2 * t)
  c1mc2 = c1 - c2
  c1mc2.dot(c1mc2)
end

#draw ⇒ Object 



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# File 'lib/pongo/spring_constraint_particle.rb', line 51

def draw
  #throw NotImplementedError
end

#elasticity ⇒ Object 



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

def elasticity
  (@p1.elasticity * @p2.elasticity) / 2.0
end

#fixed? ⇒ Boolean Also known as: fixed

Returns:

  • (Boolean) 


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# File 'lib/pongo/spring_constraint_particle.rb', line 67

def fixed?
  @parent.fixed?
end

#friction ⇒ Object 



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# File 'lib/pongo/spring_constraint_particle.rb', line 37

def friction
  (@p1.friction * @p2.friction) / 2.0
end

#get_contact_point_param(p) ⇒ Object Also known as: contact_point_param

returns a contact location on this SCP expressed as a parametric value in [0,1]



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# File 'lib/pongo/spring_constraint_particle.rb', line 134

def get_contact_point_param(p)
  if p.is_a?(CircleParticle)
    closest_param_point(p.curr)
  elsif p.is_a?(RectangleParticle)
    # go through the sides of the colliding rectangle as line segments
    shortest_index = 0
    params_list = []
    shortest_distance = Numeric::POSITIVE_INFINITY
    4.times do |i|
      set_corners(p, i)

      # check for closest points on SCP to side of rectangle
      d = closest_pt_segment_segment
      if d < shortest_distance
        shortest_distance = d
        shortest_index = i
        params_list[i] = @s
      end
      params_list[shortest_index]
    end
  end
end

#init ⇒ Object 



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

def init
  #throw NotImplementedError
end

#init_display ⇒ Object 



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

def init_display
  #throw NotImplementedError
end

#inv_mass ⇒ Object 



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# File 'lib/pongo/spring_constraint_particle.rb', line 59

def inv_mass
  if @p1.fixed? and @p2.fixed?
    0
  else
    1.0 / self.mass
  end
end

#mass ⇒ Object 



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

def mass
  (@p1.mass * @p2.mass) / 2.0
end

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



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# File 'lib/pongo/spring_constraint_particle.rb', line 82

def resolve_collision(mtd, vel, n, d, o, p)
  test_particle_events(p)
  return if fixed? or not p.solid?

  t = contact_point_param(p)
  c1 = 1 -t
  c2 = t

  # if one is fixed then move the other particle the entire way out of 
  # collision. also, dispose of collisions at the sides of the scp. The higher
  # the fixedEndLimit value, the more of the scp not be effected by collision. 
  if @p1.fixed?
    return if c2 <= @fixed_end_limit
    lamda.set_to(mtd.x / c2, mtd.y / c2)
    @p2.curr.plus!(lamda)
    @p2.velocity = vel
  elsif @p2.fixed?
    return if c1 <= @fixed_end_limit
    lamda.set_to(mtd.x / c1, mtd.y / c1)
    @p1.curr.plus!(lamda)
    @p1.velocity = vel
  else
    # else both non fixed - move proportionally out of collision
    denom = c1 * c1 + c2 * c2
    return if denom == 0
    lamda.set_to(mtd.x / denom, mtd.y / denom)

    @p1.curr.plus!(lamda * c1)
    @p2.curr.plus!(lamda * c2)
    
    if t == 0.5
      # if collision is in the middle of SCP set the velocity of both end 
      # particles
      @p1.velocity = vel
      @p2.velocity = vel
    else
      # otherwise change the velocity of the particle closest to contact
      corr_particle = t < 0.5 ? @p1 : @p2
      corr_particle.velocity = vel
    end
  end
end

#set_corners(r, i) ⇒ Object 



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# File 'lib/pongo/spring_constraint_particle.rb', line 158

def set_corners(r, i)
  rx = r.curr.x
  ry = r.curr.y

  axes = r.axes
  extents = r.extents

  ae0_x = axes[0].x * extents[0]
  ae0_y = axes[0].y * extents[0]
  ae1_x = axes[1].x * extents[1]
  ae1_y = axes[1].y * extents[1]

  emx = ae0_x - ae1_x
  emy = ae0_y - ae1_y
  epx = ae0_x + ae1_x
  epy = ae0_y + ae1_y

  case i
  when 0
    # 0 and 1
    @rca.x = rx - epx;
    @rca.y = ry - epy;
    @rcb.x = rx + emx;
    @rcb.y = ry + emy;
  when 1
    # 1 and 2
    @rca.x = rx + emx;
    @rca.y = ry + emy;
    @rcb.x = rx + epx;
    @rcb.y = ry + epy;
  when 2
    # 2 and 3
    @rca.x = rx + epx;
    @rca.y = ry + epy;
    @rcb.x = rx - emx;
    @rcb.y = ry - emy;
  when 3
    # 3 and 0
    @rca.x = rx - emx;
    @rca.y = ry - emy;
    @rcb.x = rx - epx;
    @rcb.y = ry - epy;
  end
end

#update_position ⇒ Object

called only on collision



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# File 'lib/pongo/spring_constraint_particle.rb', line 73

def update_position
  @curr.set_to(@parent.center)
  self.width = @scale_to_length \
    ? @parent.curr_length * @rect_scale \
    : @parent.rest_length * @rect_scale
  self.height = @rect_height
  self.radian = @parent.radian
end

#velocity ⇒ Object 



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# File 'lib/pongo/spring_constraint_particle.rb', line 41

def velocity
  p1v = @p1.velocity
  p2v = @p2.velocity
  @avg_velocity.set_to((p1v.x + p2v.x) / 2.0, (p1v.y + p2v.y) / 2.0)
end