mirror of
https://gitlab.com/gaelysam/mapgen_rivers.git
synced 2024-12-29 12:20:41 +01:00
112 lines
2.3 KiB
Lua
112 lines
2.3 KiB
Lua
-- gaussian.lua
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local function get_box_size(sigma, n)
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local v = sigma^2 / n
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--print('v: '..v)
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local r_ideal = ((12*v + 1) ^ 0.5 - 1) / 2
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--print('r_ideal: '..r_ideal)
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local r_down = math.floor(r_ideal)
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--print('r_down: '..r_down)
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local r_up = math.ceil(r_ideal)
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--print('r_up: '..r_up)
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local v_down = ((2*r_down+1)^2 - 1) / 12
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--print('v_down: '..v_down)
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local v_up = ((2*r_up+1)^2 - 1) / 12
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--print('v_up: '..v_up)
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local m_ideal = (v - v_down) / (v_up - v_down) * n
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--print('m_ideal: '..m_ideal)
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local m = math.floor(m_ideal+0.5)
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--print('m: '..m)
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local sizes = {}
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for i=1, n do
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sizes[i] = i<=m and 2*r_up+1 or 2*r_down+1
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end
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--print('sizes: '..table.concat(sizes, ', '))
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return sizes
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end
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local function box_blur_1d(map, size, first, incr, len, map2)
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local n = math.ceil(size/2)
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first = first or 1
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incr = incr or 1
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len = len or math.floor((#map-first)/incr)+1
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local last = first + (len-1)*incr
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local nth = first+(n-1)*incr
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local sum = 0
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for i=first, nth, incr do
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if i == first then
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sum = sum + map[i]
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else
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sum = sum + 2*map[i]
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end
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end
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local i_left = nth
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local incr_left = -incr
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local i_right = nth
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local incr_right = incr
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map2 = map2 or {}
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for i=first, last, incr do
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map2[i] = sum / size
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i_right = i_right + incr_right
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sum = sum - map[i_left] + map[i_right]
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i_left = i_left + incr_left
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if i_left == first then
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incr_left = incr
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end
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if i_right == last then
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incr_right = -incr
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end
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end
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return map2
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end
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local function box_blur_2d(map1, size, map2)
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local X, Y = map1.X, map1.Y
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map2 = map2 or {}
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for y=1, Y do
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box_blur_1d(map1, size, (y-1)*X+1, 1, X, map2)
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end
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for x=1, X do
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box_blur_1d(map2, size, x, X, Y, map1)
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end
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return map1
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end
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--[[local function gaussian_blur(map, std, tail)
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local exp = math.exp
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local kernel_mid = math.ceil(std*tail) + 1
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local kernel_size = kernel_mid * 2 - 1
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local kernel = {}
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local cst1 = 1/(std*(2*math.pi)^0.5)
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local cst2 = -1/(2*std^2)
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for i=1, kernel_size do
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kernel[i] = cst1 * exp((i-kernel_mid)^2 * cst2)
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end
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]]
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local function gaussian_blur_approx(map, sigma, n, map2)
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map2 = map2 or {}
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local sizes = get_box_size(sigma, n)
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for i=1, n do
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box_blur_2d(map, sizes[i], map2)
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end
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return map
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end
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return {
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get_box_size = get_box_size,
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box_blur_1d = box_blur_1d,
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box_blur_2d = box_blur_2d,
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gaussian_blur_approx = gaussian_blur_approx,
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}
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