Class: Geometry::Polyline

Inherits:
Object
  • Object
show all
Defined in:
lib/geometry/polyline.rb

Overview

A Polyline is like a Polygon in that it only contains straight lines, but also like a Path in that it isn’t necessarily closed.

http://en.wikipedia.org/wiki/Polyline

Usage

Direct Known Subclasses

Polygon

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(Edge, Edge, ...) ⇒ Polyline #initialize(Point, Point, ...) ⇒ Polyline

Construct a new Polyline from Points and/or Edges

The constructor will try to convert all of its arguments into {Point}s and
 {Edge}s. Then successive {Point}s will be collpased into {Edge}s. Successive
 {Edge}s that share a common vertex will be added to the new {Polyline}. If
 there's a gap between {Edge}s it will be automatically filled with a new
 {Edge}.

Overloads:

  • #initialize(Edge, Edge, ...) ⇒ Polyline
  • #initialize(Point, Point, ...) ⇒ Polyline 


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# File 'lib/geometry/polyline.rb', line 28

def initialize(*args)
    args.map! {|a| (a.is_a?(Array) || a.is_a?(Vector)) ? Point[a] : a}
    args.each {|a| raise ArgumentError, "Unknown argument type #{a.class}" unless a.is_a?(Point) or a.is_a?(Edge) }

    @edges = [];
    @vertices = [];

    first = args.shift
    if first.is_a?(Point)
  @vertices.push first
    elsif first.is_a?(Edge)
  @edges.push first
  @vertices.push *(first.to_a)
    end

    args.reduce(@vertices.last) do |previous,n|
  if n.is_a?(Point)
      if n == previous # Ignore repeated Points
    previous
      else
    if @edges.last
        new_edge = Edge.new(previous, n)
        if @edges.last.parallel?(new_edge)
      popped_edge = @edges.pop   # Remove the previous Edge
      @vertices.pop(@edges.size ? 1 : 2) # Remove the now unused vertex, or vertices
      if n == popped_edge.first
          popped_edge.first
      else
          push_edge Edge.new(popped_edge.first, n)
          push_vertex popped_edge.first
          push_vertex n
          n
      end
        else
      push_edge Edge.new(previous, n)
      push_vertex n
      n
        end
    else
        push_edge Edge.new(previous, n)
        push_vertex n
        n
    end
      end
  elsif n.is_a?(Edge)
      if previous == n.first
    push_edge n
    push_vertex n.last
      elsif previous == n.last
    push_edge n.reverse!
    push_vertex n.last
      else
    e = Edge.new(previous, n.first)
    push_edge e, n
    push_vertex *(e.to_a), *(n.to_a)
      end
      n.last
  end
    end
end

Instance Attribute Details

#edges ⇒ Object (readonly)

Returns the value of attribute edges.



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# File 'lib/geometry/polyline.rb', line 16

def edges
  @edges
end

#vertices ⇒ Object (readonly)

Returns the value of attribute vertices.



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# File 'lib/geometry/polyline.rb', line 16

def vertices
  @vertices
end

Instance Method Details

#eql?(other) ⇒ Bool Also known as: ==

Check the equality of two Geometry::Polylines. Note that if two Geometry::Polylines have

opposite winding, but are otherwise identical, they will be considered unequal.

Returns:



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# File 'lib/geometry/polyline.rb', line 92

def eql?(other)
    @vertices.zip(other.vertices).all? {|a,b| a == b}
end

#offset(distance) ⇒ Polygon Also known as: leftset

Offset the receiver by the specified distance. A positive distance

will offset to the left, and a negative distance to the right.

Parameters:

  • distance (Number) —

    The distance to offset by

Returns:



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# File 'lib/geometry/polyline.rb', line 101

def offset(distance)
    bisectors = offset_bisectors(distance)
    offsets = bisectors.each_cons(2).to_a

    # Create the offset edges and then wrap them in Hashes so the edges
    #  can be altered while walking the array
    active_edges = edges.zip(offsets).map do |e,offset|
  offset = Edge.new(e.first+offset.first.vector, e.last+offset.last.vector)

  # Skip zero-length edges
  {:edge => (offset.first == offset.last) ? nil : offset}
    end

    # Walk the array and handle any intersections
    for i in 0..(active_edges.count-1) do
  e1 = active_edges[i][:edge]
  next unless e1 # Ignore deleted edges

  intersection, j = find_last_intersection(active_edges, i, e1)
  if intersection
      e2 = active_edges[j][:edge]
      if intersection.is_a? Point
    active_edges[i][:edge] = Edge.new(e1.first, intersection)
    active_edges[j][:edge] = Edge.new(intersection, e2.last)
      else
    # Handle the collinear case
    active_edges[i][:edge] = Edge.new(e1.first, e2.last)
    active_edges[j].delete(:edge)
      end

      # Delete everything between e1 and e2
      for k in i..j do
    next if (k==i) or (k==j)    # Exclude e1 and e2
    active_edges[k].delete(:edge)
      end

      redo    # Recheck the modified edges
  end
    end
    Polyline.new *(active_edges.map {|e| e[:edge]}.compact.map {|e| [e.first, e.last]}.flatten)
end

#rightset(distance) ⇒ Polygon

Rightset the receiver by the specified distance

Parameters:

  • distance (Number) —

    The distance to offset by

Returns:



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# File 'lib/geometry/polyline.rb', line 147

def rightset(distance)
    offset(-distance)
end