103 lines
2.2 KiB
Lua
103 lines
2.2 KiB
Lua
-- bounds.lua
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local function get_bounds(dirs, rivers)
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local X, Y = dirs.X, dirs.Y
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local bounds_x = {X=X, Y=Y}
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local bounds_y = {X=X, Y=Y}
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for i=1, X*Y do
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bounds_x[i] = 0
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bounds_y[i] = 0
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end
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for i=1, X*Y do
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local dir = dirs[i]
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local river = rivers[i]
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if dir == 1 then -- South (+Y)
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bounds_y[i] = river
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elseif dir == 2 then -- East (+X)
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bounds_x[i] = river
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elseif dir == 3 then -- North (-Y)
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bounds_y[i-X] = river
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elseif dir == 4 then -- West (-X)
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bounds_x[i-1] = river
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end
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end
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return bounds_x, bounds_y
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end
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local function twist(dirs, rivers, n)
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n = n or 5
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local X, Y = dirs.X, dirs.Y
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local bounds_x, bounds_y = get_bounds(dirs, rivers)
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local dn = 0.5 / n
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local offset_x = {X=X, Y=Y}
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local offset_y = {X=X, Y=Y}
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local offset_x_alt = {X=X, Y=Y}
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local offset_y_alt = {X=X, Y=Y}
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for i=1, X*Y do
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offset_x[i] = 0
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offset_y[i] = 0
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end
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for nn=1, n do
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local i = 1
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for y=1, Y do
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for x=1, X do
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local ox, oy = offset_x[i], offset_y[i]
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if dirs[i] ~= 0 and rivers[i] > 1 then
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local sum_fx = 0
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local sum_fy = 0
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local sum_w = 0
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local b
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if x < X then
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b = bounds_x[i]
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sum_fx = sum_fx + b*(offset_x[i+1]+1)
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sum_fy = sum_fy + b*offset_y[i+1]
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sum_w = sum_w + b
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end
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if y < Y then
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b = bounds_y[i]
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sum_fx = sum_fx + b*offset_x[i+X]
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sum_fy = sum_fy + b*(offset_y[i+X]+1)
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sum_w = sum_w + b
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end
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if x > 1 then
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b = bounds_x[i-1]
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sum_fx = sum_fx + b*(offset_x[i-1]-1)
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sum_fy = sum_fy + b*offset_y[i-1]
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sum_w = sum_w + b
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end
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if y > 1 then
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b = bounds_y[i-X]
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sum_fx = sum_fx + b*offset_x[i-X]
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sum_fy = sum_fy + b*(offset_y[i-X]-1)
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sum_w = sum_w + b
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end
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local fx, fy = sum_fx/sum_w - ox, sum_fy/sum_w - oy
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local fd = (fx*fx+fy*fy) ^ 0.5
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if fd > dn then
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local c = dn/fd
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fx, fy = fx*c, fy*c
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end
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offset_x_alt[i] = ox+fx
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offset_y_alt[i] = oy+fy
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else
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offset_x_alt[i] = ox
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offset_y_alt[i] = oy
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end
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i = i + 1
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end
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end
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offset_x, offset_x_alt = offset_x_alt, offset_x
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offset_y, offset_y_alt = offset_y_alt, offset_y
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end
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return offset_x, offset_y
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end
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return twist
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