This is the solution I used to build the quiz movie. It works in a
Unix terminal and it can generate PPM images:
#!/usr/bin/env ruby -w
class SimFrost
def initialize(width, height, vapor)
@ticks = 0
@grid = Array.new(height) do
Array.new(width) { rand(100) < vapor ? "." : " " }
end
@grid[height / 2][width / 2] = "*"
end
attr_reader :ticks
def width
@grid.first.size
end
def height
@grid.size
end
def tick
(tick_start...height).step(2) do |y|
(tick_start...width).step(2) do |x|
cells = [ [x, y ],
[wrap_x(x + 1), y ],
[wrap_x(x + 1), wrap_y(y + 1)],
[x, wrap_y(y + 1)] ]
if cells.any? { |xy| cell(xy) == "*" }
cells.select { |xy| cell(xy) == "." }.each { |xy| cell(xy,
"*") }
else
rotated = cells.dup
if rand(2).zero?
rotated.push(rotated.shift)
else
rotated.unshift(rotated.pop)
end
new_cells = rotated.map { |xy| cell(xy) }
cells.zip(new_cells) { |xy, value| cell(xy, value) }
end
end
end
@ticks += 1
end
def complete?
not @grid.flatten.include? "."
end
def to_s
@grid.map { |row| row.join }.join("\n")
end
private
def tick_start; (@ticks % 2).zero? ? 0 : 1 end
def wrap_x(x) x % width end
def wrap_y(y) y % height end
def cell(xy, value = nil)
if value
@grid[xy.last][xy.first] = value
else
@grid[xy.last][xy.first]
end
end
end
class UnixTerminalDisplay
BLUE = "\e[34m"
WHITE = "\e[37m"
ON_BLACK = "\e[40m"
CLEAR = "\e[0m"
def initialize(simulator)
@simulator = simulator
end
def clear
@clear ||= `clear`
end
def display
print clear
puts @simulator.to_s.gsub(/\.+/, "#{BLUE + ON_BLACK}\\&#{CLEAR}").
gsub(/\*+/, "#{WHITE + ON_BLACK}\\&#{CLEAR}").
gsub(/ +/, "#{ ON_BLACK}\\&#{CLEAR}")
end
end
class PPMImageDisplay
BLUE = [0, 0, 255].pack("C*")
WHITE = [255, 255, 255].pack("C*")
BLACK = [0, 0, 0 ].pack("C*")
def initialize(simulator, directory)
@simulator = simulator
@directory = directory
Dir.mkdir directory unless File.exist? directory
end
def display
File.open(file_name, "w") do |image|
image.puts "P6"
image.puts "#{@simulator.width} #{@simulator.height} 255"
@simulator.to_s.each_byte do |cell|
case cell.chr
when "." then image.print BLUE
when "*" then image.print WHITE
when " " then image.print BLACK
else next
end
end
end
end
private
def file_name
File.join(@directory, "%04d.ppm" % @simulator.ticks)
end
end
if __FILE__ == $PROGRAM_NAME
require "optparse"
options = { :width => 80,
:height => 22,
:vapor => 30,
utput => UnixTerminalDisplay,
:directory => "frost_images" }
ARGV.options do |opts|
opts.banner = "Usage: #{File.basename($PROGRAM_NAME)} [OPTIONS]"
opts.separator ""
opts.separator "Specific Options:"
opts.on( "-w", "--width EVEN_INT", Integer,
"Sets the width for the simulation." ) do |width|
options[:width] = width
end
opts.on( "-h", "--height EVEN_INT", Integer,
"Sets the height for the simulation." ) do |height|
options[:height] = height
end
opts.on( "-v", "--vapor PERCENT_INT", Integer,
"The percent of the grid filled with vapor." ) do |vapor|
options[:vapor] = vapor
end
opts.on( "-t", "--terminal",
"Unix terminal display (default)." ) do
options[
utput] = UnixTerminalDisplay
end
opts.on( "-i", "--image",
"PPM image series display." ) do
options[
utput] = PPMImageDisplay
end
opts.on( "-d", "--directory", String,
"Where to place PPM image files. ",
%Q{Defaults to "frost_images".} ) do |directory|
options[:directory] = directory
end
opts.separator "Common Options:"
opts.on( "-?", "--help",
"Show this message." ) do
puts opts
exit
end
begin
opts.parse!
rescue
puts opts
exit
end
end
simulator = SimFrost.new(options[:width], options[:height], options
[:vapor])
setup = options[
utput] == PPMImageDisplay ?
[simulator, options[:directory]] :
[simulator]
terminal = options[
utput].new(*setup)
terminal.display
until simulator.complete?
sleep 0.5 if options[
utput] == UnixTerminalDisplay
simulator.tick
terminal.display
end
end
__END__
James Edward Gray II
