mapgen_rivers/terrainlib_lua/twist.lua
2022-01-07 14:48:36 +01:00

103 lines
2.2 KiB
Lua

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