├── README.textile
└── fire.rb


/README.textile:
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 1 | h2. Fire in Ruby Processing
 2 | 
 3 | This code draws fire with a simple algorithm in "Ruby Processing":http://wiki.github.com/jashkenas/ruby-processing
 4 | 
 5 | !http://dl.getdropbox.com/u/221414/blogs/burn_baby.png!
 6 | 
 7 | Here's a video: "Fire video":http://screencast.com/t/69TnHrKqG4
 8 | 
 9 | h3. Algorithm:
10 | 
11 | 1. Create an indexed palette of red, orange and yellows
12 | 
13 | 2. Loop over the following:
14 | 
15 | * Draw a random set of colours from the palette at the bottom of the screen
16 | * Loop through each pixel and average the colour index value around it
17 | * Reduce the average by a fire intensity factor
18 | 
19 | 


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/fire.rb:
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  1 | # Fire
  2 | 
  3 | # Algorithm:
  4 | #   1. Create an indexed palette of red, orange and yellows
  5 | #   2. Loop:
  6 | #   3.   Draw a random set of colours from the palette at the bottom of the screen
  7 | #   4.   Loop through each pixel and average the colour index value around it
  8 | #   5.   Reduce the average by a fire intensity factor
  9 | 
 10 | # rp5 run fire.rb
 11 | 
 12 | class Fire < Processing::App
 13 | 
 14 |   def setup
 15 |     color_mode RGB, 255
 16 |     background 0
 17 |     frame_rate 30
 18 | 
 19 |     @palette = make_palette
 20 |     @fire = []
 21 | 
 22 |     @scale = 8
 23 |     @width = width / @scale
 24 |     @height = height / @scale
 25 | 
 26 |     @intensity = 2
 27 |   end
 28 |   
 29 |   def draw
 30 |     update_fire
 31 |   end
 32 | 
 33 |   def update_fire
 34 |     random_line @height - 1
 35 |     (0..@height - 2).each do |y|
 36 |       (0..@width).each do |x|
 37 |         # Wrap
 38 |         left = (x == 0) ? fire_data(@width - 1, y) : fire_data(x - 1, y)
 39 |         right = (x == @width - 1) ? fire_data(0, y) : fire_data(x + 1, y)
 40 |         below = fire_data(x, y + 1)
 41 | 
 42 |         # Get the average pixel value
 43 |         average = (left.to_i + right.to_i + (below.to_i * 2)) / 4
 44 | 
 45 |         # Fade the flames
 46 |         average -= @intensity if average > @intensity
 47 | 
 48 |         set_fire_data x, y, average
 49 | 
 50 |         fill color(*@palette[average])
 51 |         stroke color(*@palette[average])
 52 | 
 53 |         rect x * @scale, (y + 1) * @scale, @scale, @scale
 54 |       end
 55 |     end
 56 |   end
 57 | 
 58 |   def fire_data(x, y)
 59 |     @fire[offset(x, y)]
 60 |   end
 61 | 
 62 |   def set_fire_data(x, y, value)
 63 |     @fire[offset(x, y)] = value
 64 |   end
 65 | 
 66 |   def make_palette
 67 |     palette = []
 68 |     # Create the bands of colour for the palette (256 is the maximum colour)
 69 |     limit = 64
 70 |     multiplier = 256 / limit
 71 |     (0..limit).each do |i|
 72 |       # Range of reds
 73 |       palette[i] = [i * multiplier, 0, 0]
 74 |       # Orange
 75 |       palette[i + limit] = [255, i * multiplier, 0]
 76 |       # Yellow
 77 |       palette[i + limit * 2] = [255, 255, i * multiplier]
 78 |       # Also try making this white, I prefer a strong red (in wine terms too)
 79 |       palette[i + limit * 3] = [180, 0, 0]
 80 |     end
 81 |     palette
 82 |   end
 83 |   
 84 |   def random_colour
 85 |     color *@palette[rand(@palette.size)]
 86 |   end
 87 | 
 88 |   def random_offset
 89 |     rand @palette.size
 90 |   end
 91 | 
 92 |   def random_line(y)
 93 |     (0..@width - 1).each do |x|
 94 |       @fire[offset(x, y)] = random_offset
 95 |     end
 96 |   end
 97 | 
 98 |   def offset(x, y)
 99 |     (y * @width) + x
100 |   end
101 | end
102 | 
103 | Fire.new :title => "Fire", :width => 320, :height => 240
104 | 


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