mapgen_rivers/terrainlib_lua/rivermapper.lua

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-- rivermapper.lua
local function flow_local_semirandom(plist)
local sum = 0
for i=1, #plist do
sum = sum + plist[i]
end
--for _, p in ipairs(plist) do
--sum = sum + p
--end
if sum == 0 then
return 0
end
local r = math.random() * sum
for i=1, #plist do
local p = plist[i]
--for i, p in ipairs(plist) do
if r < p then
return i
end
r = r - p
end
return 0
end
local flow_methods = {
semirandom = flow_local_semirandom,
}
local function flow_routing(dem, dirs, lakes, method)
method = method or 'semirandom'
local flow_local = flow_methods[method] or flow_local_semirandom
dirs = dirs or {}
lakes = lakes or {}
-- Localize for performance
--local tinsert = table.insert
local tremove = table.remove
local mmax = math.max
local X, Y = dem.X, dem.Y
dirs.X = X
dirs.Y = Y
lakes.X = X
lakes.Y = Y
local i = 1
local dirs2 = {}
for i=1, X*Y do
dirs2[i] = 0
end
local singular = {}
for y=1, Y do
for x=1, X do
local zi = dem[i]
local plist = {
y<Y and mmax(zi-dem[i+X], 0) or 0, -- Southward
x<X and mmax(zi-dem[i+1], 0) or 0, -- Eastward
y>1 and mmax(zi-dem[i-X], 0) or 0, -- Northward
x>1 and mmax(zi-dem[i-1], 0) or 0, -- Westward
}
local d = flow_local(plist)
dirs[i] = d
if d == 0 then
singular[#singular+1] = i
elseif d == 1 then
dirs2[i+X] = dirs2[i+X] + 1
elseif d == 2 then
dirs2[i+1] = dirs2[i+1] + 2
elseif d == 3 then
dirs2[i-X] = dirs2[i-X] + 4
elseif d == 4 then
dirs2[i-1] = dirs2[i-1] + 8
end
i = i + 1
end
end
-- Compute basins and links
local nbasins = #singular
local basin_id = {}
local links = {}
local basin_links
local function add_link(i1, i2, b1, isY)
local b2
if i2 == 0 then
b2 = 0
else
b2 = basin_id[i2]
if b2 == 0 then
return
end
end
if b2 ~= b1 then
local elev = i2 == 0 and dem[i1] or mmax(dem[i1], dem[i2])
local l2 = basin_links[b2]
if not l2 then
l2 = {}
basin_links[b2] = l2
end
if not l2.elev or l2.elev > elev then
l2.elev = elev
l2.i = mmax(i1,i2)
l2.is_y = isY
l2[1] = b2
l2[2] = b1
end
end
end
for i=1, X*Y do
basin_id[i] = 0
end
--for ib, s in ipairs(singular) do
for ib=1, nbasins do
--local s = singular[ib]
local queue = {singular[ib]}
basin_links = {}
links[#links+1] = basin_links
--tinsert(links, basin_links)
while #queue > 0 do
local i = tremove(queue)
basin_id[i] = ib
local d = dirs2[i]
if d >= 8 then -- River coming from East
d = d - 8
queue[#queue+1] = i+1
--tinsert(queue, i+X)
elseif i%X > 0 then
add_link(i, i+1, ib, false)
else
add_link(i, 0, ib, false)
end
if d >= 4 then -- River coming from South
d = d - 4
queue[#queue+1] = i+X
--tinsert(queue, i+1)
elseif i <= X*(Y-1) then
add_link(i, i+X, ib, true)
else
add_link(i, 0, ib, true)
end
if d >= 2 then -- River coming from West
d = d - 2
queue[#queue+1] = i-1
--tinsert(queue, i-X)
elseif i%X ~= 1 then
add_link(i, i-1, ib, false)
else
add_link(i, 0, ib, false)
end
if d >= 1 then -- River coming from North
queue[#queue+1] = i-X
--tinsert(queue, i-1)
elseif i > X then
add_link(i, i-X, ib, true)
else
add_link(i, 0, ib, true)
end
end
end
dirs2 = nil
links[0] = {}
local nlinks = {}
for i=0, nbasins do
nlinks[i] = 0
end
--for ib1, blinks in ipairs(links) do
for ib1=1, #links do
for ib2, link in pairs(links[ib1]) do
if ib2 < ib1 then
links[ib2][ib1] = link
nlinks[ib1] = nlinks[ib1] + 1
nlinks[ib2] = nlinks[ib2] + 1
end
end
end
local lowlevel = {}
for i, n in pairs(nlinks) do
if n <= 8 then
lowlevel[i] = links[i]
end
end
local basin_graph = {}
for n=1, nbasins do
local b1, lnk1 = next(lowlevel)
lowlevel[b1] = nil
local b2
local lowest = math.huge
local lnk1 = links[b1]
local i = 0
for bn, bdata in pairs(lnk1) do
i = i + 1
if bdata.elev < lowest then
lowest = bdata.elev
b2 = bn
end
end
-- Add link to the graph
local bound = lnk1[b2]
local bb1, bb2 = bound[1], bound[2]
if not basin_graph[bb1] then
basin_graph[bb1] = {}
end
if not basin_graph[bb2] then
basin_graph[bb2] = {}
end
basin_graph[bb1][bb2] = bound
basin_graph[bb2][bb1] = bound
-- Merge basin b1 into b2
local lnk2 = links[b2]
-- First, remove the link between b1 and b2
lnk1[b2] = nil
lnk2[b1] = nil
nlinks[b2] = nlinks[b2] - 1
if nlinks[b2] == 8 then
lowlevel[b2] = lnk2
end
-- Look for basin 1's neighbours, and add them to basin 2 if they have a lower pass
for bn, bdata in pairs(lnk1) do
local lnkn = links[bn]
lnkn[b1] = nil
if lnkn[b2] then
nlinks[bn] = nlinks[bn] - 1
if nlinks[bn] == 8 then
lowlevel[bn] = lnkn
end
else
nlinks[b2] = nlinks[b2] + 1
if nlinks[b2] == 9 then
lowlevel[b2] = nil
end
end
if not lnkn[b2] or lnkn[b2].elev > bdata.elev then
lnkn[b2] = bdata
lnk2[bn] = bdata
end
end
end
local queue = {[0] = -math.huge}
local basin_lake = {}
for n=1, nbasins do
basin_lake[n] = 0
end
local reverse = {3, 4, 1, 2, [0]=0}
for n=1, nbasins do
local b1, elev1 = next(queue)
queue[b1] = nil
basin_lake[b1] = elev1
for b2, bound in pairs(basin_graph[b1]) do
-- Make b2 flow into b1
local i = bound.i
local dir = bound.is_y and 3 or 4
if basin_id[i] ~= b2 then
dir = dir - 2
if bound.is_y then
i = i - X
else
i = i - 1
end
elseif b1 == 0 then
dir = 0
end
repeat
dir, dirs[i] = dirs[i], dir
if dir == 1 then
i = i + X
elseif dir == 2 then
i = i + 1
elseif dir == 3 then
i = i - X
elseif dir == 4 then
i = i - 1
end
dir = reverse[dir]
until dir == 0
-- Add b2 into the queue
queue[b2] = mmax(elev1, bound.elev)
basin_graph[b2][b1] = nil
end
basin_graph[b1] = nil
end
for i=1, X*Y do
lakes[i] = basin_lake[basin_id[i]]
end
return dirs, lakes
end
local function accumulate(dirs, waterq)
waterq = waterq or {}
local X, Y = dirs.X, dirs.Y
--local tinsert = table.insert
local ndonors = {}
local waterq = {X=X, Y=Y}
for i=1, X*Y do
ndonors[i] = 0
waterq[i] = 1
end
--for i1, dir in ipairs(dirs) do
for i1=1, X*Y do
local i2
local dir = dirs[i1]
if dir == 1 then
i2 = i1+X
elseif dir == 2 then
i2 = i1+1
elseif dir == 3 then
i2 = i1-X
elseif dir == 4 then
i2 = i1-1
end
if i2 then
ndonors[i2] = ndonors[i2] + 1
end
end
for i1=1, X*Y do
if ndonors[i1] == 0 then
local i2 = i1
local dir = dirs[i2]
local w = waterq[i2]
while dir > 0 do
if dir == 1 then
i2 = i2 + X
elseif dir == 2 then
i2 = i2 + 1
elseif dir == 3 then
i2 = i2 - X
elseif dir == 4 then
i2 = i2 - 1
end
w = w + waterq[i2]
waterq[i2] = w
if ndonors[i2] > 1 then
ndonors[i2] = ndonors[i2] - 1
break
end
dir = dirs[i2]
end
end
end
return waterq
end
return {
flow_routing = flow_routing,
accumulate = accumulate,
flow_methods = flow_methods,
}