August/September Entry: Portolan Chart

[Hai-Etlik]

hello you... any chance you`d share that little rhumb program?? me wants it very bad!

#!/usr/bin/ruby1.9.1

require 'matrix'

p=4

n=2**p

d1=600
d2=4*d1



points=Array.new(n) do |k|
  theta=2*Math::PI*k/n
  
  x=d1*Math.cos(theta)
  y=d1*Math.sin(theta)

  Vector[x,y]
end

def line(p1,p2,style)
  "<path d=\"M#{p1.to_a.join " "} L#{p2.to_a.join " "}\" style=\"#{style}\" />"
end

puts <<EOS
<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">

<svg version="1.1"
xmlns="http://www.w3.org/2000/svg">
EOS

n.times do |k|
  p1=points[k]
  (k...n).each do |l|#<path d="M250 150 L150 350 L350 350 Z" />
    style=(k+l)%2==0? "stroke:black;stroke-width:0.5px;":"stroke:red;stroke-width:0.5px;"

    opacity="opacity:#{rand*0.5+0.5}"
    p2=points[l]
    v=p1-p2
    v=v*d2*(1.0/v.r)
    p3=p1+v
    p4=p2-v

    # p4 - p2 - p1 - p3

    print line(p1, p2, style+opacity)
    
    print line(p4, p2, style+opacity)
    
    puts line(p1, p3, style+opacity)

  end
  style="stroke:black;stroke-width:0.5px;"

  theta=2*Math::PI*(k+n/4)/n

  x=d2*Math.cos(theta)
  y=d2*Math.sin(theta)

  v=Vector[x,y]
  
  p2=p1+v
  p3=p1-v

  opacity="opacity:#{rand*0.5+0.5}"

  print line(p1, p2, style+opacity)
  puts line(p1, p3, style+opacity)
  
end

puts "</svg>"