ravello_round.rhtml

<%

require './helpers.rb'

size = 500
thickness = 25
angle = -Math::PI*0.75

s1 = 50
s0 = s1 * Math.tan(Math::PI/8)
s2 = s1 + 2*s0

base_chain = [p(s0,s1), p(s2,s1), p(s2,-s1)]
base_commands = [' L ', " A #{s1} #{s1} 0 0 0 "]

chain = (0...8).map do |step|
  base_chain.zip(base_commands).map { |(p, c)| p.rotate2d(step * angle).to2d_s + (c || "") }.join
end.join(' L ')

stroke_dashes = StrokeDash.new(-10,40,99,99,60.48)

page_intro("Ravello Round Knot")

%>
<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" version="1.1" xml:lang="en" viewBox="<%= -size/2 %> <%= -size/2 %> <%= size %> <%= size %>" id="knot">
  <defs>
    <style>
      .top, .bottom { stroke-width: <%= thickness %>px; fill: none; }
      .top { stroke: #E09989; }
      .bottom { stroke: #E8E1D3; }
      .top { <%= stroke_dashes.css %> }
    </style>
    <path id="path-a" d="M <%= chain %> Z" />
  </defs>
  <use xlink:href="#path-a" class="bottom" />
  <use xlink:href="#path-a" class="top" />
</svg>