Module: Arbiter

Included in:
Stage
Defined in:
lib/gamebox/core/arbiter.rb

Overview

this module gets mixed into a stage to allow it to handle collision detection

Instance Attribute Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#checks ⇒ Object (readonly)

Returns the value of attribute checks.



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# File 'lib/gamebox/core/arbiter.rb', line 3

def checks
  @checks
end

#collisions ⇒ Object (readonly)

Returns the value of attribute collisions.



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# File 'lib/gamebox/core/arbiter.rb', line 3

def collisions
  @collisions
end

Instance Method Details

#aabb_tree ⇒ Object 



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# File 'lib/gamebox/core/arbiter.rb', line 13

def aabb_tree
  @aabb_tree ||= SpatialTree.new(self)
end

#circle_interval(axis, object) ⇒ Object 



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# File 'lib/gamebox/core/arbiter.rb', line 184

def circle_interval(axis, object)
  axis_x = axis[0]
  axis_y = axis[1]

  obj_x = object.center_x
  obj_y = object.center_y

  length = Math.sqrt(axis_x * axis_x + axis_y * axis_y)
  cn = axis_x*obj_x + axis_y*obj_y
  rlength = object.radius*length
  min = cn - rlength
  max = cn + rlength
  [min,max]
end

#collide?(object, other) ⇒ Boolean

This reads terribly and violates open-closed principle, but does perform better than any dynamic lookup based on shape_types

Returns:

  • (Boolean) 


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# File 'lib/gamebox/core/arbiter.rb', line 102

def collide?(object, other)
  case object.shape_type
  when :circle
    case other.shape_type
    when :circle
      collide_circle_circle? object, other
    when :aabb
      collide_circle_aabb? object, other
    when :polygon
      collide_circle_polygon? object, other
    end
  when :aabb
    case other.shape_type
    when :circle
      collide_aabb_circle? object, other
    when :aabb
      collide_aabb_aabb? object, other
    when :polygon
      collide_aabb_polygon? object, other
    end
  when :polygon
    case other.shape_type
    when :circle
      collide_polygon_circle? object, other
    when :aabb
      collide_polygon_aabb? object, other
    when :polygon
      collide_polygon_polygon? object, other
    end
  end
end

#collide_circle_circle?(object, other) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/gamebox/core/arbiter.rb', line 134

def collide_circle_circle?(object, other)
  x_delta = other.center_x - object.center_x
  x_dist  = x_delta * x_delta
  y_delta = other.center_y - object.center_y
  y_dist  = y_delta * y_delta

  total_radius = object.radius + other.radius
  (x_dist + y_dist) <= (total_radius * total_radius)
end

#collide_circle_polygon?(object, other) ⇒ Boolean Also known as: collide_circle_aabb?

Returns:

  • (Boolean) 


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# File 'lib/gamebox/core/arbiter.rb', line 204

def collide_circle_polygon?(object, other)
  if collide_circle_circle? object, other
    potential_sep_axis = other.cw_world_edge_normals
    potential_sep_axis.each do |axis|
      return false unless project_and_detect(axis, object, other)           
    end 
    true 
  else
    false
  end
end

#collide_polygon_circle?(object, other) ⇒ Boolean Also known as: collide_aabb_circle?

Returns:

  • (Boolean) 


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# File 'lib/gamebox/core/arbiter.rb', line 199

def collide_polygon_circle?(object, other)
  collide_circle_polygon?(other, object)
end

#collide_polygon_polygon?(object, other) ⇒ Boolean Also known as: collide_aabb_aabb?

Idea from: gpwiki.org/index.php/Polygon_Collision and www.gamedev.net/community/forums/topic.asp?topic_id=540755&whichpage=1&#3488866

Returns:

  • (Boolean) 


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# File 'lib/gamebox/core/arbiter.rb', line 147

def collide_polygon_polygon?(object, other)
  if collide_circle_circle? object, other
    # collect vector's perp
    potential_sep_axis = 
      (object.cw_world_edge_normals | other.cw_world_edge_normals).uniq
    potential_sep_axis.each do |axis|
      return false unless project_and_detect(axis, object, other)           
    end 
  else
    return false
  end
  true
end

#find_collisions ⇒ Object 



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# File 'lib/gamebox/core/arbiter.rb', line 65

def find_collisions
  collidable_actors = aabb_tree.moved_items.values

  collisions = {}

  collidable_actors.each do |first|
    # if first.is? :collidable
      # HUH? it appears that querying modifies the tree somehow?
      aabb_tree.collisions(first) do |second|

        # if second.is? :collidable
          if first != second &&
            interested_in_collision_of?(first.actor_type, second.actor_type) &&
            collide?(first, second)
            if !collisions[second] || (collisions[second] && !collisions[second].include?(first))
              collisions[first] ||= []
              collisions[first] << second
            end
        #   end
        # end
      end
    end
  end
  unique_collisions = []
  collisions.each do |first,seconds|
    seconds.each do |second|
      unique_collisions << [first,second]
    end
  end
  run_callbacks unique_collisions
  aabb_tree.reset
end

#interested_in_collision_of?(type1, type2) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/gamebox/core/arbiter.rb', line 59

def interested_in_collision_of?(type1, type2)
  @collision_handlers ||= {}
  (@collision_handlers[type1] && @collision_handlers[type1][type2]) ||
  (@collision_handlers[type2] && @collision_handlers[type2][type1])
end

#on_collision_of(first_objs, second_objs, &block) ⇒ Object 



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# File 'lib/gamebox/core/arbiter.rb', line 17

def on_collision_of(first_objs, second_objs, &block)
  first_objs = [first_objs].flatten
  second_objs = [second_objs].flatten

  @collision_handlers ||= {}

  first_objs.each do |fobj|
    second_objs.each do |sobj|
      if fobj < sobj
        @collision_handlers[fobj] ||= {}
        @collision_handlers[fobj][sobj] = [false,block]
      else
        @collision_handlers[sobj] ||= {}
        @collision_handlers[sobj][fobj] = [true,block]
      end
    end
  end
end

#polygon_interval(axis, object) ⇒ Object Also known as: aabb_interval 



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# File 'lib/gamebox/core/arbiter.rb', line 170

def polygon_interval(axis, object)
  min = max = nil
  object.cw_world_points.each do |edge|
    # vector dot product
    d = edge[0] * axis[0] + edge[1] * axis[1]
    min ||= d
    max ||= d
    min = d if d < min
    max = d if d > max
  end
  [min,max]
end

#project_and_detect(axis, a, b) ⇒ Object

returns true if the projections overlap



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# File 'lib/gamebox/core/arbiter.rb', line 163

def project_and_detect(axis, a, b)
  a_min, a_max = send("#{a.shape_type}_interval", axis, a)
  b_min, b_max = send("#{b.shape_type}_interval", axis, b)

  a_min <= b_max && b_min <= a_max
end

#register_collidable(actor) ⇒ Object 



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# File 'lib/gamebox/core/arbiter.rb', line 5

def register_collidable(actor)
  aabb_tree.add(actor)
end

#run_callbacks(collisions) ⇒ Object 



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# File 'lib/gamebox/core/arbiter.rb', line 36

def run_callbacks(collisions)
  @collision_handlers ||= {}
  collisions.each do |collision|
    first = collision.first
    second = collision.last
    unless first.actor_type < second.actor_type
      tmp = first
      first = second
      second = tmp
    end

    colliders = @collision_handlers[first.actor_type]
    swapped, callback = colliders[second.actor_type] unless colliders.nil?
    unless callback.nil?
      if swapped
        callback.call second, first 
      else
        callback.call first, second 
      end
    end
  end
end

#unregister_collidable(actor) ⇒ Object 



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# File 'lib/gamebox/core/arbiter.rb', line 9

def unregister_collidable(actor)
  aabb_tree.remove(actor)
end