Pixel Fireplace

Flow description

# @name Pixel Fireplace
# @desc Full-screen procedural pixel fire
# @version 2.0

class PixelFireplace

 var a,b,seed,last

 def init()
  self.seed=now_ms()+4517
  self.last=0
  self.a=[]
  self.b=[]

  for i:0..255
   self.a.push(0)
   self.b.push(0)
  end
 end

 def rnd(n)
  self.seed=(self.seed*1103515245+12345)%2147483647
  if self.seed<0 self.seed=-self.seed end
  return self.seed%n
 end


 # =====================================
 # FIRE PHYSICS
 # =====================================

 def update()

  var n=now_ms()
  if n-self.last<75 return end
  self.last=n


  # -----------------------------------
  # FIRE BED
  #
  # Constant heat along bottom with
  # random darker holes and hot spots.
  # -----------------------------------

  for x:0..31

   var h=190+self.rnd(66)

   if self.rnd(8)==0
    h=80+self.rnd(80)
   end

   self.a[224+x]=h

  end


  # extra white-hot pockets

  for i:0..5
   var x=2+self.rnd(28)
   self.a[224+x]=255
  end


  # -----------------------------------
  # PROPAGATE HEAT UPWARD
  # -----------------------------------

  for y:0..6

   for x:0..31

    var below=(y+1)*32+x
    var h=self.a[below]

    # mix nearby heat

    if x>0
     h+=self.a[below-1]
    else
     h+=self.a[below]
    end

    if x<31
     h+=self.a[below+1]
    else
     h+=self.a[below]
    end

    # heat two rows below makes
    # taller connected flames

    if y<6
     var yy=y+2
     if yy>7 yy=7 end
     h+=self.a[yy*32+x]
    end

    h=h/4


    # cooling increases toward top

    var cool=10+self.rnd(22)

    if y<3
     cool+=10
    end

    h-=cool

    if h<0 h=0 end


    # sideways turbulence

    var dx=0
    var r=self.rnd(5)

    if r==0 dx=-1 end
    if r==4 dx=1 end

    var xx=x+dx
    if xx<0 xx=0 end
    if xx>31 xx=31 end

    self.b[y*32+xx]=h

   end

  end


  # bottom remains combustion layer

  for x:0..31
   self.b[224+x]=self.a[224+x]
  end


  # swap buffers

  var q=self.a
  self.a=self.b
  self.b=q

 end


 # =====================================
 # HEAT -> FIRE COLOR
 # =====================================

 def dot(x,y,h)

  if h<18
   return
  end

  var c=0

  # deep ember
  if h<55
   c=0x260000

  # dark red
  elif h<90
   c=0x600000

  # red
  elif h<125
   c=0xB01000

  # orange/red
  elif h<165
   c=0xFF2800

  # orange
  elif h<200
   c=0xFF7000

  # yellow
  elif h<230
   c=0xFFC000

  # yellow-white
  elif h<248
   c=0xFFFF40

  # hottest core
  else
   c=0xFFFFD0
  end

  pixel(x,y,c)

 end


 # =====================================
 # EMBERS
 # =====================================

 def embers()

  # occasional isolated hot pixels
  # above the main flames

  if self.rnd(3)==0

   var x=3+self.rnd(26)
   var y=self.rnd(4)

   if self.rnd(3)==0
    pixel(x,y,0xFFFF80)
   else
    pixel(x,y,0xFF5000)
   end

  end

 end


 # =====================================
 # LOG / COAL BED
 # =====================================

 def bed()

  # dark irregular foreground

  pixel(0,7,0x240800)
  pixel(1,7,0x451000)
  pixel(2,7,0x701500)
  pixel(3,7,0x301000)

  pixel(6,7,0x701500)
  pixel(7,7,0xA02000)
  pixel(8,7,0x451000)

  pixel(11,7,0x8A1800)
  pixel(12,7,0xD03000)
  pixel(13,7,0x601000)

  pixel(16,7,0xA02000)
  pixel(17,7,0xF04000)
  pixel(18,7,0x701500)

  pixel(21,7,0x701500)
  pixel(22,7,0xC02800)
  pixel(23,7,0x501000)

  pixel(26,7,0x901800)
  pixel(27,7,0xD03000)
  pixel(28,7,0x601000)

  pixel(30,7,0x401000)
  pixel(31,7,0x200800)

 end


 # =====================================
 # DRAW
 # =====================================

 def draw()

  self.update()

  clear(0x010000)

  for y:0..7
   for x:0..31
    self.dot(x,y,self.a[y*32+x])
   end
  end

  self.embers()
  self.bed()

 end

end

return PixelFireplace()