mtcontrib/mapgen_rivers
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Flow routing: Initialize basin_graph + comment where complexity might be non-linear

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Gaël C 2024-01-22 11:06:03 +01:00
parent 4bce5fab77
commit f350f8785c
1 changed files with 19 additions and 9 deletions
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28
terrainlib_lua/rivermapper.lua
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@ -111,6 +111,10 @@ local function flow_routing(dem, dirs, lakes) -- 'dirs' and 'lakes' are optional
local d = dirs2[i] -- Get the directions water is coming from local d = dirs2[i] -- Get the directions water is coming from
-- Iterate through the 4 directions -- Iterate through the 4 directions
-- Loop is unrolled on purpose, for performance (critical part!)
----------
-- EAST --
----------
if d >= 8 then -- River coming from the East if d >= 8 then -- River coming from the East
d = d - 8 d = d - 8
cur = cur + 1 cur = cur + 1
@ -123,7 +127,7 @@ local function flow_routing(dem, dirs, lakes) -- 'dirs' and 'lakes' are optional
local l2 = basin_links[b2] local l2 = basin_links[b2]
if not l2 then if not l2 then
l2 = {b2, ib, elev=elev, i=i+1, is_y=false} l2 = {b2, ib, elev=elev, i=i+1, is_y=false}
basin_links[b2] = l2 basin_links[b2] = l2 -- Potential non-linear complexity here
elseif l2.elev > elev then -- If this link is lower than the lowest registered link between these two basins, register it as the new lowest pass elseif l2.elev > elev then -- If this link is lower than the lowest registered link between these two basins, register it as the new lowest pass
l2.elev = elev l2.elev = elev
l2.i = i+1 l2.i = i+1
@ -146,6 +150,9 @@ local function flow_routing(dem, dirs, lakes) -- 'dirs' and 'lakes' are optional
end end
end end
-----------
-- SOUTH --
-----------
if d >= 4 then -- River coming from the South if d >= 4 then -- River coming from the South
d = d - 4 d = d - 4
cur = cur + 1 cur = cur + 1
@ -180,6 +187,9 @@ local function flow_routing(dem, dirs, lakes) -- 'dirs' and 'lakes' are optional
end end
end end
----------
-- WEST --
----------
if d >= 2 then -- River coming from the West if d >= 2 then -- River coming from the West
d = d - 2 d = d - 2
cur = cur + 1 cur = cur + 1
@ -214,6 +224,9 @@ local function flow_routing(dem, dirs, lakes) -- 'dirs' and 'lakes' are optional
end end
end end
-----------
-- NORTH --
-----------
if d >= 1 then -- River coming from the North if d >= 1 then -- River coming from the North
cur = cur + 1 cur = cur + 1
singular[cur] = i-X singular[cur] = i-X
@ -287,7 +300,10 @@ local function flow_routing(dem, dirs, lakes) -- 'dirs' and 'lakes' are optional
end end
local basin_graph = {} local basin_graph = {}
while cur > 1 do for i=0, nbasins do
basin_graph[i] = {} -- Initialize (to ensure subtables don't go in the hash part)
end
for i=1, nbasins do
-- Iterate in lowlevel but its contents may change during the loop -- Iterate in lowlevel but its contents may change during the loop
local b1 = lowlevel[cur] local b1 = lowlevel[cur]
cur = cur - 1 cur = cur - 1
@ -307,13 +323,7 @@ local function flow_routing(dem, dirs, lakes) -- 'dirs' and 'lakes' are optional
-- Add link to the graph, in both directions -- Add link to the graph, in both directions
local bound = lnk1[b2] local bound = lnk1[b2]
local bb1, bb2 = bound[1], bound[2] local bb1, bb2 = bound[1], bound[2]
if not basin_graph[bb1] then basin_graph[bb1][bb2] = bound -- Potential non-linear complexity here
basin_graph[bb1] = {}
end
if not basin_graph[bb2] then
basin_graph[bb2] = {}
end
basin_graph[bb1][bb2] = bound
basin_graph[bb2][bb1] = bound basin_graph[bb2][bb1] = bound
-- Merge basin b1 into b2 -- Merge basin b1 into b2