Class: Geospatial::Polygon

Inherits:
Object
  • Object
show all
Defined in:
lib/geospatial/polygon.rb

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(points, bounding_box = nil) ⇒ Polygon

Returns a new instance of Polygon.



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# File 'lib/geospatial/polygon.rb', line 43

def initialize(points, bounding_box = nil)
	@points = points
	@bounding_box = bounding_box
end

Instance Attribute Details

#points ⇒ Object (readonly)

Returns the value of attribute points.



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# File 'lib/geospatial/polygon.rb', line 48

def points
  @points
end

Class Method Details

.[](*points) ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 27

def self.[] *points
	self.new(points)
end

.dump(polygon) ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 37

def self.dump(polygon)
	if polygon
		JSON.dump(polygon.points.map(&:to_a))
	end
end

.is_left(p0, p1, p2) ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 144

def self.is_left(p0, p1, p2)
	a = p1 - p0
	b = p2 - p0
	
	return (a[0] * b[1]) - (b[0] * a[1])
end

.load(data) ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 31

def self.load(data)
	if data
		self.new(JSON.parse(data).map{|point| Vector.elements(point)})
	end
end

Instance Method Details

#[](index) ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 50

def [] index
	a = @points[index.floor]
	b = @points[index.ceil % @points.size]
	
	return a + (b - a) * (index % 1.0)
end

#area(radius = 1.0) ⇒ Object

Parameters:

  • radius (Float) (defaults to: 1.0) —

    The radius of the sphere on which to compute the area.



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# File 'lib/geospatial/polygon.rb', line 83

def area(radius = 1.0)
	if @points.size > 2
		area = 0.0
		
		self.edges.each do |p1, p2|
			r1 = (p2[0] - p1[0]) * D2R
			r2 = 2 + Math::sin(p1[1] * D2R) + Math::sin(p2[1] * D2R)
			
			area += r1 * r2
		end
		
		return (area * radius * radius / 2.0).abs
	else
		return 0.0
	end
end

#bounding_box ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 61

def bounding_box
	@bounding_box ||= Box.enclosing_points(@points).freeze
end

#edge_intersection(a, b) ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 187

def edge_intersection(a, b)
	line = Line.new(a, b)
	
	edges.each_with_index do |(pa, pb), i|
		edge = Line.new(pa, pb)
		
		if line.intersect?(edge)
			return i
		end
	end
	
	return nil
end

#edges ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 72

def edges
	return to_enum(:edges) unless block_given?
	
	size = @points.size
	
	@points.each_with_index do |point, index|
		yield point, @points[(index+1)%size]
	end
end

#freeze ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 65

def freeze
	@points.freeze
	bounding_box.freeze
	
	super
end

#include?(other) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/geospatial/polygon.rb', line 210

def include?(other)
	other.corners.all?{|corner| self.include_point?(corner)}
end

#include_point?(point) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/geospatial/polygon.rb', line 173

def include_point?(point)
	return false unless bounding_box.include_point?(point)
	
	self.winding_number(point).odd?
end

#intersect?(other) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/geospatial/polygon.rb', line 201

def intersect?(other)
	case other
	when Box
		intersect_with_box?(other)
	when Circle
		intersect_with_circle?(other)
	end
end

#intersect_with_box?(other) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/geospatial/polygon.rb', line 179

def intersect_with_box?(other)
	return true if @points.any?{|point| other.include_point?(point)}
	
	return true if other.corners.any?{|corner| self.include_point?(corner)}
	
	return false
end

#simplify ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 100

def simplify
	simplified_points = @points.first(1)
	
	(1...@points.size).each do |index|
		point = @points[index]
		
		next_point = @points[(index+1) % @points.size]
		
		if yield(simplified_points.last, point, next_point)
			simplified_points << point
		end
	end
	
	self.class.new(simplified_points, bounding_box)
end

#subdivide ⇒ Object

polygon.subdivide do |a, b| a = Geospatial::Location.new(*a) b = Geospatial::Location.new(*b) if a.distance_from(b) > maximum_distance a.midpoints(b, 2) end end



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# File 'lib/geospatial/polygon.rb', line 124

def subdivide
	simplified_points = @points.first(1)
	
	(1..@points.size).each do |index|
		point = @points[index % @points.size]
		next_point = @points[(index+1) % @points.size]
		
		if points = yield(simplified_points.last, point, next_point)
			simplified_points.concat(points)
		end
		
		# Polygons are represented by a closed sequence of points, but we need to subdivide by the last point at the first point too. However, we don't add the first point a 2nd time.
		if index < @points.size
			simplified_points << point
		end
	end
	
	self.class.new(simplified_points, bounding_box)
end

#to_s ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 57

def to_s
	"#{self.class}#{@points.inspect}"
end

#winding_number(p) ⇒ Number

Test a 2D point for inclusion in the polygon.

Parameters:

  • p (Vector) —

    The point to test.

Returns:

  • (Number) —

    The number of times the polygon winds around the point (0 if outside).



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# File 'lib/geospatial/polygon.rb', line 154

def winding_number(p)
	count = 0
	
	edges.each do |pa, pb|
		if pa[1] <= p[1]
			if pb[1] >= p[1] and Polygon.is_left(pa, pb, p) > 0
				count += 1
			end
		else
			if pb[1] <= p[1] and Polygon.is_left(pa, pb, p) < 0
				count -= 1
			end
		end
		
	end
	
	return count
end