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Drawing Polar Grids

Drawing Polar Grids

Learn to draw polar grids in Ruby.

We'll cover the following...

The PolarGrid class

The to_png method we’ve used up to this point isn’t going to help us much with polar grids, so let’s just subclass Grid and rewrite to_png to be what we need it to be. We'll create a new file named polar_grid.rb. We’ll add the Grid subclass and to_png method to our file.

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require 'grid'
class PolarGrid < Grid 
  def to_png_v1(cell_size: 10)
    img_size = 2 * @rows * cell_size 
    background = ChunkyPNG::Color::WHITE
    wall = ChunkyPNG::Color::BLACK
    img = ChunkyPNG::Image.new(img_size + 1, img_size + 1, background)
    center = img_size / 2 
    each_cell do |cell|
      theta        = 2 * Math::PI / @grid[cell.row].length 
      inner_radius = cell.row * cell_size
      outer_radius = (cell.row + 1) * cell_size
      theta_ccw    = cell.column * theta
      theta_cw     = (cell.column + 1) * theta 
      ax = center + (inner_radius * Math.cos(theta_ccw)).to_i 
      ay = center + (inner_radius * Math.sin(theta_ccw)).to_i
      bx = center + (outer_radius * Math.cos(theta_ccw)).to_i
      by = center + (outer_radius * Math.sin(theta_ccw)).to_i
      cx = center + (inner_radius * Math.cos(theta_cw)).to_i
      cy = center + (inner_radius * Math.sin(theta_cw)).to_i
      dx = center + (outer_radius * Math.cos(theta_cw)).to_i
      dy = center + (outer_radius * Math.sin(theta_cw)).to_i 
      img.line(ax, ay, cx, cy, wall) unless cell.linked?(cell.north) 
      img.line(cx, cy, dx, dy, wall) unless cell.linked?(cell.east) 
    end
    img.circle(center, center, @rows * cell_size, wall) 
    img
  end
end

Code explanation

Line 4: This new to_png method starts much like the old version, computing the size of our canvas.

Line 5: In this case, though, ...