Class: Geospatial::Polygon

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

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(points) ⇒ Polygon

Returns a new instance of Polygon.



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# File 'lib/geospatial/polygon.rb', line 29

def initialize(points)
	@points = points
	@box = nil
end

Class Method Details

.[](*points) ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 25

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

.is_left(p0, p1, p2) ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 59

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

Instance Method Details

#bounding_box ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 38

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

#edges ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 49

def edges
	return to_enum(:edges) unless block_given?
	
	previous = @points.last
	@points.each do |point|
		yield previous, point
		previous = point
	end
end

#freeze ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 42

def freeze
	@points.freeze
	bounding_box.freeze
	
	super
end

#include?(other) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/geospatial/polygon.rb', line 111

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 88

def include_point?(point)
	return false unless bounding_box.include_point?(point)
	
	self.winding_number(point) == 1
end

#intersect?(other) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/geospatial/polygon.rb', line 102

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 94

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

#to_s ⇒ Object 



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# File 'lib/geospatial/polygon.rb', line 34

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 69

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