133 lines
3.5 KiB
Lua
133 lines
3.5 KiB
Lua
-- Generates an image using multiple octaves of perlin noise.
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local args = {...}
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local rng = dfhack.random.new(3)
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if #args < 3 then
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qerror('Usage: devel/test-perlin <fname.pgm> <density> <coeff|expr...x[...y[...z]]>...')
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end
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local fname = table.remove(args,1)
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local goal = tonumber(table.remove(args,1)) or qerror('Invalid density')
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local zscale = 6
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local coeffs = {}
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local fns = {}
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local env = copyall(math)
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env.apow = function(x,y) return math.pow(math.abs(x),y) end
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for i = 1,#args do
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local fn = rng:perlin(3);
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local fn2 = rng:perlin(3);
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local fn3 = rng:perlin(3);
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local fn4 = rng:perlin(3);
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fns[i] = fn;
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local val = string.match(args[i],'^([+-]?[%d.]+)$')
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if val then
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coeffs[i] = function(x) return x * val end
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else
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local argstr = 'x'
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if string.match(args[i], '%f[%w]w%f[^%w]') then
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argstr = 'x,y,z,w'
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fns[i] = function(x,y,z)
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return fn(x,y,z), fn2(x,y,z), fn3(x+0.5,y+0.5,z+0.5), fn4(x+0.5,y+0.5,z+0.5)
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end
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elseif string.match(args[i], '%f[%w]z%f[^%w]') then
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argstr = 'x,y,z'
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fns[i] = function(x,y,z)
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return fn(x,y,z), fn2(x,y,z), fn3(x+0.5,y+0.5,z+0.5)
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end
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elseif string.match(args[i], '%f[%w]y%f[^%w]') then
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argstr = 'x,y'
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fns[i] = function(x,y,z)
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return fn(x,y,z), fn2(x,y,z)
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end
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end
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local f,err = load(
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'return function('..argstr..') return ('..args[i]..') end',
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'=(expr)', 't', env
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)
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if not f then
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qerror(err)
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end
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coeffs[i] = f()
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end
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end
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function render(thresh,file)
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local area = 0
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local line, arr = '', {}
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for zy = 0,1 do
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for y = 0,48*4-1 do
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line = ''
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for zx = 0,1 do
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for x = 0,48*4-1 do
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local tx = (0.5+x)/(48*2)
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local ty = (0.5+y)/(48*2)
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local tz = 0.5+(zx+zy*2)/(48*2/zscale)
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local v1 = 0
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for i = 1,#coeffs do
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v1 = v1 + coeffs[i](fns[i](tx,ty,tz))
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tx = tx*2
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ty = ty*2
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tz = tz*2
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end
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local v = -1
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if v1 > thresh then
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v = v1;
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area = area + 1
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end
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if file then
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local c = math.max(0, math.min(255, v * 127 + 128))
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arr[2*x+1] = c
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arr[2*x+2] = c
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end
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end
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if file then
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line = line..string.char(table.unpack(arr))
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end
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end
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if file then
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file:write(line,line)
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end
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end
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end
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return area/4/(48*4)/(48*4)
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end
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function search(fn,min,max,goal,eps)
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while true do
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local center = (max+min)/2
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local cval = fn(center)
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print('At '..center..': '..cval)
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if math.abs(cval-goal) < eps then
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return center
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end
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if cval > goal then
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min = center
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else
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max = center
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end
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end
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end
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local thresh = search(render, -1, 1, goal, 0.001)
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local file,err = io.open(fname, 'wb')
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if not file then
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print('error: ',err)
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return
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end
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file:write('P5\n768 768\n255\n')
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local area = render(thresh, file)
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file:close()
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print('Area fraction: '..area)
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