From 6d8ee5af1f743ddc21fc82f6d1ca7c753bcfdde3 Mon Sep 17 00:00:00 2001
From: Gael-de-Sailly <gael-de-sailly@netc.eu>
Date: Mon, 3 Jan 2022 15:45:27 +0100
Subject: [PATCH] Added settings for margin, and documented in settingtypes.txt

---
 heightmap.lua         |  6 +++---
 pregenerate.lua       |  6 +++---
 settings.lua          |  3 +++
 settings_default.json |  3 +++
 settingtypes.txt      | 10 ++++++++++
 5 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/heightmap.lua b/heightmap.lua
index cbe8923..d6b2303 100644
--- a/heightmap.lua
+++ b/heightmap.lua
@@ -6,7 +6,7 @@ local transform_quadri = dofile(modpath .. 'geometry.lua')
 local sea_level = mapgen_rivers.settings.sea_level
 local riverbed_slope = mapgen_rivers.settings.riverbed_slope * mapgen_rivers.settings.blocksize
 
-local MAP_BOTTOM = -31000
+local out_elev = mapgen_rivers.settings.margin_elev
 
 -- Localize for performance
 local floor, min, max = math.floor, math.min, math.max
@@ -128,8 +128,8 @@ local function heightmaps(minp, maxp)
 				terrain_height_map[i] = terrain_height
 				lake_height_map[i] = lake_height
 			else
-				terrain_height_map[i] = MAP_BOTTOM
-				lake_height_map[i] = MAP_BOTTOM
+				terrain_height_map[i] = out_elev
+				lake_height_map[i] = out_elev
 			end
 			i = i + 1
 		end
diff --git a/pregenerate.lua b/pregenerate.lua
index 7334385..30ed915 100644
--- a/pregenerate.lua
+++ b/pregenerate.lua
@@ -14,9 +14,9 @@ local time_step = mapgen_rivers.settings.evol_time_step
 local niter = math.ceil(time/time_step)
 time_step = time / niter
 
-local use_margin = true
-local margin_width = 2000 / blocksize
-local margin_elev = -200
+local use_margin = mapgen_rivers.settings.margin
+local margin_width = mapgen_rivers.settings.margin_width / blocksize
+local margin_elev = mapgen_rivers.settings.margin_elev
 
 local function margin(dem, width, elev)
 	local X, Y = dem.X, dem.Y
diff --git a/settings.lua b/settings.lua
index a7aee00..c5e66f8 100644
--- a/settings.lua
+++ b/settings.lua
@@ -95,6 +95,9 @@ mapgen_rivers.settings = {
 
 	map_x_size = def_setting('map_x_size', 'number'),
 	map_z_size = def_setting('map_z_size', 'number'),
+	margin = def_setting('margin', 'bool'),
+	margin_width = def_setting('margin_width', 'number'),
+	margin_elev = def_setting('margin_elev', 'number'),
 	evol_params = {
 		K = def_setting('river_erosion_coef', 'number'),
 		m = def_setting('river_erosion_power', 'number'),
diff --git a/settings_default.json b/settings_default.json
index 9b63edc..3e937c7 100644
--- a/settings_default.json
+++ b/settings_default.json
@@ -15,6 +15,9 @@
 
 	"map_x_size": 15000,
 	"map_z_size": 15000,
+	"margin": true,
+	"margin_width": 2000,
+	"margin_elev": -200,
 	"river_erosion_coef": 0.5,
 	"river_erosion_power": 0.4,
 	"diffusive_erosion": 0.5,
diff --git a/settingtypes.txt b/settingtypes.txt
index 6446541..44b0290 100644
--- a/settingtypes.txt
+++ b/settingtypes.txt
@@ -23,6 +23,16 @@ mapgen_rivers_map_x_size (Map X size) int 15000 500 66000
 #    When increasing, it is recommended to increase blocksize too
 mapgen_rivers_map_z_size (Map Z size) int 15000 500 66000
 
+#    If margin is enabled, elevation becomes closer to a fixed value when approaching
+#    the edges of the map.
+mapgen_rivers_margin (Margin) bool true
+
+#    Width of the transition at map borders, in nodes
+mapgen_rivers_margin_width (Margin width) float 2000.0 0.0 15000.0
+
+#    Elevation toward which to converge at map borders
+mapgen_rivers_margin_elev (Margin elevation) float -200.0 -31000.0 31000.0
+
 #    Minimal catchment area for a river to be drawn, in square nodes
 #    Lower value means bigger river density
 mapgen_rivers_min_catchment (Minimal catchment area) float 3600.0 100.0 1000000.0