A laser-cuttable circular slide rule generator

slide.rb

#!/usr/bin/env ruby

Maths = Math

Radius = ARGV.shift&.to_f || 50.0
Ring = ARGV.shift&.to_f || 15.0

Decimals = 6
Origin_x = Radius + Ring + 1
Origin_y = Radius + Ring + 1

Page_x = 2 * 2 * Origin_x
Page_y = 2 * Origin_y

def a_preamble(page_x, page_y)
  puts <<-EOT % [page_x, page_y, page_x, page_y]
<?xml version="1.0" encoding="UTF-8" standalone="no"?>

<svg
  width="%dmm"
  height="%dmm"
  viewBox="0 0 %d %d"
  version="1.1"
  xmlns="http://www.w3.org/2000/svg"
  xmlns:svg="http://www.w3.org/2000/svg"
>
  <g>
  EOT
end

def a_postamble
  puts <<-EOT
  </g>
</svg>
  EOT
end

def a_circle(origin_x, origin_y, radius)
  puts <<-EOT % [origin_x, origin_y, radius, radius]
    <ellipse
      style="fill:none;stroke:#FF0000;stroke-width:0.1"
      cx="%.6f"
      cy="%.6f"
      rx="%.6f"
      ry="%.6f"
    />
  EOT
end

def a_mark(xf, yf, xt, yt)
  puts <<-EOT % [xf, yf, xt, yt]
    <path
      style="fill:none;stroke:#0000FF;stroke-width:0.1"
      d="M %.6f,%.6f %.6f,%.6f"
    />
  EOT
end

def a_label(origin_x, origin_y, radius, heading, mod, ticktext)
  xt = origin_x + (radius * Maths.cos(heading) * (1 + mod))
  yt = origin_y + (radius * Maths.sin(heading) * (1 + mod))
  puts <<-EOT % [xt, yt, ticktext]
    <text
      xml:space="preserve"
      style="fill:#000000;stroke:none;font-size:1.5px;font-family:'Google Sans'"
      x="%.6f"
      y="%.6f"
      text-anchor="middle"
    >%s</text>
  EOT
end

def a_double_label(origin_x, origin_y, radius, heading, mod, ticktext)
  a_label(origin_x, origin_y, radius, heading, -mod, ticktext)
  a_label(origin_x, origin_y, radius, heading, mod, ticktext)
end

def a_tick(mantissa, exponent, origin_x, origin_y, radius, intervals)
  scale = Maths::PI * 2 / intervals
  (0..0.9).step(0.1).each do |sub|
    tick = mantissa * (10 ** exponent) + sub
    heading = scale * (exponent + Maths.log10(mantissa + sub))

    adj = case mantissa + sub
        when *[1.0,5.0]
          0.06
        when *[2.0,3.0,4.0,6.0,7.0,8.0,9.0]
          0.04
        else
          0.02
        end
    xi = origin_x + (radius * Maths.cos(heading) * (1 - adj))
    yi = origin_y + (radius * Maths.sin(heading) * (1 - adj))
    xo = origin_x + (radius * Maths.cos(heading) * (1 + adj))
    yo = origin_y + (radius * Maths.sin(heading) * (1 + adj))

    ticktext = if tick == 1.0
                 "#{tick.to_i}(#{"0" * intervals})"
               else 
                 "#{tick.to_i}"
               end

    a_mark(xi, yi, xo, yo)
    a_double_label(origin_x, origin_y, radius, heading, adj + 0.04, ticktext) if sub == 0
  end
end

def a_scale(origin_x, origin_y, radius, intervals)
  intervals.times do |exponent|
    (1..9).each do |mantissa|
      a_tick(mantissa, exponent, origin_x, origin_y, radius, intervals)
    end
  end
end

a_preamble(Page_x + 1, Page_y + 1)

a_circle(Origin_x, Origin_y, Radius)
a_circle(Origin_x, Origin_y, Radius + Ring)
a_circle(Origin_x + (2 * (Radius + Ring + 1)), Origin_y, Radius + Ring)
a_circle(Origin_x, Origin_y, Radius - Ring)

a_double_label(Origin_x, Origin_y, Radius - Ring, 0.05, 0.1, "x")
a_scale(Origin_x, Origin_y, Radius - Ring, 1)

a_double_label(Origin_x, Origin_y, Radius, 0.04, 0.1, "x^2")
a_scale(Origin_x, Origin_y, Radius, 2)

a_postamble