fire effect (cc lua)

--[[
fire effect
code by GopherAtl, 2013

No rights reserved, DWYW.
--]]

local w,h=term.getSize()

local dithers={
 " ",
 ".",
 "-",
 "+",
 "%",
 "*",
 "#",
 "@",
}


local ranges= {
  { colors.black, colors.gray, },
  { colors.gray, colors.red, },
  { colors.red, colors.orange, },
  { colors.orange, colors.yellow, },
}

local coolWeight=75

if not term.isColor() then
  ranges={
    { colors.black,colors.white },
  }
  coolWeight=25
end

local numDithers=(#dithers*2-1)
local max_bright=#ranges*numDithers


function genShaded(brightness)
  --break into color group
  local bgColor=colors.black
  local fgColor=colors.black
  local char=" "

  if brightness>=max_bright then
    bgColor=ranges[#ranges][2]
    fgColor=ranges[#ranges][1]
  else
    local dither=brightness%numDithers
    local range=(brightness-dither)/numDithers
    local inv=false
    bgColor=ranges[range+1][1]
    fgColor=ranges[range+1][2]
    if dither>=#dithers then
      dither=2*#dithers-dither-1
      local t=bgColor
      bgColor=fgColor
      fgColor=t
    end
    char=dithers[dither+1]
  end

  --[[term.setBackgroundColor(bgColor)
  term.setTextColor(fgColor)
  term.write(char)--]]
  return bgColor,fgColor,char
end

local precalc_shade={}

for i=0,max_bright do
  precalc_shade[i]={genShaded(i)}
end

dither=true

function drawShaded(bright)
  bright=math.floor(bright+.5)
  if bright>max_bright then
    bright=max_bright
  elseif bright<0 then
    bright=0
  end
  local shading=precalc_shade[bright]
  if shading==nil then
    error("brightness "..bright.." invalid!")
  end
  term.setBackgroundColor(shading[1])
  term.setTextColor(shading[2])
  term.write(dither and shading[3] or " ")
end

local grid, gridB={},{}

for y=1,h+1 do
  grid[y]={}
  gridB[y]={}
  for x=1,w do
    grid[y][x]=0
  end
end

local coolingGrid={}

for y=1,h*4 do
  coolingGrid[y]={}
  for x=1,w*2 do
    coolingGrid[y][x]=0
  end
end

function smooth(grid)
  for y=0,(h*4-1) do
    local up=(y-1)%(h*4)+1
    local down=(y+1)%(h*4)+1
    for x=0,(w*2-1) do
      local left=(x-1)%(w*2)+1
      local right=(x+1)%(w*2)+1
      grid[y+1][x+1]=(grid[y+1][left]+grid[y+1][right]+grid[up][x+1]+grid[down][x+1])/4
    end
  end
end

for i=1,1.6*w*h do
  coolingGrid[math.random(1,h*4)][math.random(1,w*2)]=coolWeight
end

for i=1,5 do
  smooth(coolingGrid)
end

coolingOffsetY=0
coolingOffsetX=0


function smoothFlame(grid)
  for y=1,h do
    local up=math.max(0,y-1)+1
    local down=math.min((h-1),(y+1))+1
    for x=0,(w-1) do
      local left=(x-1)%w+1
      local right=(x+1)%w+1
      grid[y][x+1]=(grid[y+1][left]+grid[y+1][right]+grid[up][x+1]+grid[down][x+1])/4-coolingGrid[math.floor((y-1+coolingOffsetY)%(h*4))+1][math.floor((x+coolingOffsetX)%(w*2))+1]
    end
  end
end

function draw()
  for y=1,h do
    for x=1,w do
      term.setCursorPos(x,y)
      drawShaded(grid[y][x]/2)
    end
  end
end




for x=1,w do
  grid[h+1][x]=max_bright*2
end

for i=1,w do
  local x=math.random(1,w)
  grid[h+1][x]=max_bright*3
end

for i=1,h+1 do
  smoothFlame(grid)
end


local tick=os.startTimer(0)
while true do
  local e={os.pullEvent()}
  if e[1]=="timer" then
    draw()
    smoothFlame(grid)
    for i=1,1 do
      grid[h+1][math.random(1,w)]=max_bright*3
    end
    coolingOffsetY=(coolingOffsetY+1)%(h*4)
    coolingOffsetX=(coolingOffsetX+math.random(-2,3)/2)%(w*2)
    tick=os.startTimer(0)
  elseif e[1]=="char" then
    local ch=e[2]:lower()
    if ch=="d" then
      dither=not dither
    elseif ch=="q" then
      break
    end
  elseif e[1]=="monitor_touch" then
    dither=not dither
  end
end