From 200adcaf5af1c1344dfeb96009d44e564179bea9 Mon Sep 17 00:00:00 2001
From: beezm <celerstew@gmail.com>
Date: Fri, 7 Aug 2026 06:20:48 -0400
Subject: [PATCH] feat: config-gated flat-scalar sea level (D-033,
 terrain-water task 04)
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SeaLevelModel: "flat" (one scalar, SeaLevelValue) or "field" (the
legacy latitude Lerp 0.26..0.15). Only GetSeaLevel's body changes —
all nine call sites (crater carve target, both flood fills, biome
split, beach band, Capitol window, town filters, A* zero-point)
inherit the model automatically; no consumer re-tuning. Default:
flat 0.15, pinned in ServerConfig.json.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
---
 Core/Scripts/ConfigManager.cs | 21 +++++++++++++++++++++
 ServerConfig.json             |  4 +++-
 Tools/Scripts/MapGenerator.cs |  8 +++++++-
 3 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/Core/Scripts/ConfigManager.cs b/Core/Scripts/ConfigManager.cs
index 36800e9..35e77c7 100644
--- a/Core/Scripts/ConfigManager.cs
+++ b/Core/Scripts/ConfigManager.cs
@@ -19,6 +19,13 @@ namespace IslaApocalypse.Core // Change this if your namespace is different
 		// not a shippable world. Default false.
 		public static bool SkipRoads = false;
 
+		// Sea-level model (D-033, terrain-water task 04): "flat" = one scalar sea
+		// level everywhere (SeaLevelValue); "field" = the legacy latitude Lerp
+		// (0.26 north .. 0.15 south). Generator-only — the runtime never computes
+		// sea level. Default: flat 0.15.
+		public static string SeaLevelModel = "flat";
+		public static float SeaLevelValue = 0.15f;
+
 		public static void LoadConfig()
 		{
 			string path = "res://ServerConfig.json";
@@ -74,6 +81,20 @@ namespace IslaApocalypse.Core // Change this if your namespace is different
 				SkipRoads = (bool)data["SkipRoads"];
 			}
 
+			// Extract the sea-level model
+			if (data.ContainsKey("SeaLevelModel"))
+			{
+				string model = (string)data["SeaLevelModel"];
+				if (model == "flat" || model == "field")
+					SeaLevelModel = model;
+				else
+					GD.PrintErr($"[ConfigManager] Unknown SeaLevelModel '{model}'. Keeping '{SeaLevelModel}'.");
+			}
+			if (data.ContainsKey("SeaLevelValue"))
+			{
+				SeaLevelValue = (float)data["SeaLevelValue"];
+			}
+
 			switch (profile)
 			{
 				case "4K":
diff --git a/ServerConfig.json b/ServerConfig.json
index b9af832..7949049 100644
--- a/ServerConfig.json
+++ b/ServerConfig.json
@@ -2,5 +2,7 @@
   "WorldSeed": 1409879727,
   "MapProfile": "8K",
   "TownDensity": "Normal",
-  "ChunkRadius": 32
+  "ChunkRadius": 32,
+  "SeaLevelModel": "flat",
+  "SeaLevelValue": 0.15
 }
diff --git a/Tools/Scripts/MapGenerator.cs b/Tools/Scripts/MapGenerator.cs
index f2fb4e0..a281436 100644
--- a/Tools/Scripts/MapGenerator.cs
+++ b/Tools/Scripts/MapGenerator.cs
@@ -1212,7 +1212,13 @@ public partial class MapGenerator : TextureRect
 		return astar.GetPointPath(from, to);
 	}
 
-	private float GetSeaLevel(float t) => Mathf.Lerp(0.26f, 0.15f, Mathf.Clamp(t, 0f, 1f));
+	// Sea-level model gate (D-033, task 04): "flat" returns the configured scalar;
+	// "field" is the legacy latitude Lerp. Pure numeric mapping either way (D-035);
+	// all nine call sites inherit whichever model config selects.
+	private float GetSeaLevel(float t) =>
+		ConfigManager.SeaLevelModel == "flat"
+			? ConfigManager.SeaLevelValue
+			: Mathf.Lerp(0.26f, 0.15f, Mathf.Clamp(t, 0f, 1f));
 
 	private Vector2I FindClosestPixel(Vector2 pos, HashSet<Vector2I> set) {
 		Vector2I closest = new Vector2I(0,0); float min = float.MaxValue;