feat: 0_height hillshade snapshot + TCRV blueprint section + harness (terrain-water task 05)

0_height: hypsometric storm-ladder tint x Lambert NW hillshade over
the curved heights, captured after topography in both curve modes —
relief is finally visible. Renumbers nothing.

TCRV (50 B, emitted when the curve is on): curve version + input knots
+ output bands, so blueprints are self-describing about the map their
heights went through (H7 spirit). Parsed into
WorldBlueprint.TerrainCurve (null = raw legacy profile); server treats
it as metadata. Round-trip harness compares it when present.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Core/Scripts/BlueprintFormat.cs

@@ -32,6 +32,7 @@ namespace IslaApocalypse.Core
 		public const uint TAG_WATER_BODY_IDS   = 0x44494257; // "WBID"
 		public const uint TAG_WATER_BODY_TABLE = 0x42544257; // "WBTB"
 		public const uint TAG_WATER_SURFACE    = 0x46525357; // "WSRF"
+		public const uint TAG_TERRAIN_CURVE    = 0x56524354; // "TCRV"
 
 		// WSRF quantization: u16, 0 reserved as the no-water sentinel. A real level L
 		// (raw blueprint height units) encodes as 1 + round(L × 32768), so a genuine

Core/Scripts/BlueprintWriter.cs

@@ -31,6 +31,8 @@ namespace IslaApocalypse.Core
 				writer.Write(BlueprintFormat.VERSION);
 
 				WriteSection(writer, BlueprintFormat.TAG_PARAMS, w => WriteParams(w, bp));
+				if (bp.TerrainCurve != null)
+					WriteSection(writer, BlueprintFormat.TAG_TERRAIN_CURVE, w => WriteTerrainCurve(w, bp.TerrainCurve));
 				WriteSection(writer, BlueprintFormat.TAG_HEIGHTS, w => WriteHeights(w, bp));
 				WriteSection(writer, BlueprintFormat.TAG_BIOMES, w => WriteBiomes(w, bp));
 
@@ -122,6 +124,16 @@ namespace IslaApocalypse.Core
 			}
 		}
 
+		private static void WriteTerrainCurve(BinaryWriter writer, TerrainCurveInfo c)
+		{
+			writer.Write(c.Version);
+			writer.Write(c.T1); writer.Write(c.T2); writer.Write(c.T3); writer.Write(c.T4);
+			writer.Write(c.HMaxCal);
+			writer.Write(c.Sea); writer.Write(c.OrangeCeil); writer.Write(c.RedCeil);
+			writer.Write(c.PlateauLo); writer.Write(c.PlateauHi); writer.Write(c.PeakCap);
+			writer.Write(c.TailSlope);
+		}
+
 		private static void WriteWaterBodyIds(BinaryWriter writer, WorldBlueprint bp)
 		{
 			int n = bp.MapSize;

Core/Scripts/MapDataParser.cs

@@ -58,6 +58,20 @@ namespace IslaApocalypse.Core
 		public Vector2 Centroid;     // map pixels
 	}
 
+	/// <summary>
+	/// The height-redistribution curve that shaped this blueprint's heights (v2 TCRV
+	/// section, terrain-water task 05). Null when the blueprint was generated with the
+	/// curve off (or predates it) — heights are then the raw legacy profile. Pure
+	/// metadata: the server never re-applies the curve; exported heights are already
+	/// curved.
+	/// </summary>
+	public class TerrainCurveInfo
+	{
+		public ushort Version;
+		public float T1, T2, T3, T4, HMaxCal;                        // input knots
+		public float Sea, OrangeCeil, RedCeil, PlateauLo, PlateauHi, PeakCap, TailSlope; // output bands
+	}
+
 	public class WorldBlueprint
 	{
 		public int MapSize;
@@ -82,6 +96,9 @@ namespace IslaApocalypse.Core
 		public ushort[,] WaterBodyIds;                        // 0 = no water, 1 = ocean, 2..N = lakes
 		public List<WaterBodyInfo> WaterBodies = new List<WaterBodyInfo>();
 		public ushort[,] WaterSurfaceQ;                       // quantized levels — BlueprintFormat.DecodeWaterLevel
+
+		// The curve that shaped HeightMap (v2 TCRV section); null = raw legacy profile.
+		public TerrainCurveInfo TerrainCurve;
 	}
 
 	// 2. The Parser Utility
@@ -204,6 +221,7 @@ namespace IslaApocalypse.Core
 				else if (tag == BlueprintFormat.TAG_WATER_BODY_IDS) sectionOk = ParseWaterGrid(reader, blueprint, payloadLength, isSurface: false);
 				else if (tag == BlueprintFormat.TAG_WATER_SURFACE) sectionOk = ParseWaterGrid(reader, blueprint, payloadLength, isSurface: true);
 				else if (tag == BlueprintFormat.TAG_WATER_BODY_TABLE) sectionOk = ParseWaterBodyTable(reader, blueprint);
+				else if (tag == BlueprintFormat.TAG_TERRAIN_CURVE) sectionOk = ParseTerrainCurve(reader, blueprint);
 				else
 				{
 					// The property the redesign exists to buy: future sections (water,
@@ -366,6 +384,21 @@ namespace IslaApocalypse.Core
 			return true;
 		}
 
+		private static bool ParseTerrainCurve(BinaryReader reader, WorldBlueprint blueprint)
+		{
+			var c = new TerrainCurveInfo();
+			c.Version = reader.ReadUInt16();
+			c.T1 = reader.ReadSingle(); c.T2 = reader.ReadSingle();
+			c.T3 = reader.ReadSingle(); c.T4 = reader.ReadSingle();
+			c.HMaxCal = reader.ReadSingle();
+			c.Sea = reader.ReadSingle(); c.OrangeCeil = reader.ReadSingle();
+			c.RedCeil = reader.ReadSingle(); c.PlateauLo = reader.ReadSingle();
+			c.PlateauHi = reader.ReadSingle(); c.PeakCap = reader.ReadSingle();
+			c.TailSlope = reader.ReadSingle();
+			blueprint.TerrainCurve = c;
+			return true;
+		}
+
 		private static bool ParseRoadTier(BinaryReader reader, List<Vector2[]> into)
 		{
 			int pathCount = reader.ReadInt32();

Tools/Scripts/MapGenerator.cs

@@ -98,7 +98,10 @@ public partial class MapGenerator : TextureRect
 		// A future water stage slots in as another CaptureStage call at its own boundary.
 
 		GenerateTopography();
-		GD.Print($"{T()} Topography done (height + temperature).");
+		GD.Print($"{T()} Topography done (height + temperature). TerrainCurve: {(_curveOn ? "v1" : "off")}.");
+
+		DrawHeightStageTexture();
+		await CaptureStage("0_height");
 
 		CalculateTrueOcean();
 		CalculateMainland();
@@ -247,6 +250,15 @@ public partial class MapGenerator : TextureRect
 			TrailRoads = _trailPaths,
 			WaterBodyIds = _waterBodyIds,
 			WaterBodies = _waterBodies ?? new List<WaterBodyInfo>(),
+			TerrainCurve = _curveOn ? new TerrainCurveInfo
+			{
+				Version = HeightCurve.VERSION,
+				T1 = HeightCurve.T1, T2 = HeightCurve.T2, T3 = HeightCurve.T3, T4 = HeightCurve.T4,
+				HMaxCal = HeightCurve.HMAX_CAL,
+				Sea = HeightCurve.SEA, OrangeCeil = HeightCurve.ORANGE_CEIL, RedCeil = HeightCurve.RED_CEIL,
+				PlateauLo = HeightCurve.PLATEAU_LO, PlateauHi = HeightCurve.PLATEAU_HI,
+				PeakCap = HeightCurve.PEAK_CAP, TailSlope = HeightCurve.TAIL_SLOPE
+			} : null,
 			FormatVersion = 2,
 			Params = new BlueprintParams
 			{
@@ -749,6 +761,65 @@ public partial class MapGenerator : TextureRect
 			$"deeper than 0.01: {basinDepths.FindAll(d => d > 0.01f).Count}, deeper than 0.05: {basinDepths.FindAll(d => d > 0.05f).Count}.");
 	}
 
+	/// <summary>
+	/// Paints the height-stage snapshot (task 05): hypsometric tint by storm-ladder
+	/// band × Lambert hillshade from the height gradient (NW light), over the CURVED
+	/// heights — this is the snapshot that makes relief visible. Runs in both curve
+	/// modes; with the curve off it shows the legacy profile under the same bands.
+	/// Pure numeric pass over the heightmap.
+	/// </summary>
+	private void DrawHeightStageTexture()
+	{
+		Image img = Image.CreateEmpty(MapSize, MapSize, false, Image.Format.Rgba8);
+		Vector3 light = new Vector3(-0.55f, -0.55f, 0.63f).Normalized(); // NW, ~39° up
+
+		Color deepSea = new Color(0.07f, 0.15f, 0.32f);
+		Color shallowSea = new Color(0.25f, 0.45f, 0.65f);
+		Color green = new Color(0.44f, 0.62f, 0.36f);   // orange band terrain: lowland green
+		Color tan = new Color(0.76f, 0.70f, 0.46f);     // red band: tan
+		Color brown = new Color(0.55f, 0.41f, 0.28f);   // shoulder + plateau: brown
+		Color white = new Color(0.97f, 0.97f, 0.98f);   // peaks
+		Color grey = new Color(0.72f, 0.72f, 0.70f);
+
+		int n = MapSize;
+		for (int x = 0; x < n; x++)
+		{
+			for (int y = 0; y < n; y++)
+			{
+				float h = _heightMap[x, y];
+				float sea = GetSeaLevel(_tempMap[x, y]);
+
+				Color tint;
+				if (h < sea)
+				{
+					float depth = Mathf.Clamp((sea - h) / 0.5f, 0f, 1f);
+					tint = shallowSea.Lerp(deepSea, depth);
+				}
+				else if (h < HeightCurve.ORANGE_CEIL) tint = green;
+				else if (h < HeightCurve.RED_CEIL) tint = tan;
+				else if (h < HeightCurve.PLATEAU_HI) tint = brown;
+				else
+				{
+					float t2 = Mathf.Clamp((h - HeightCurve.PLATEAU_HI) / (HeightCurve.PEAK_CAP - HeightCurve.PLATEAU_HI), 0f, 1f);
+					tint = grey.Lerp(white, t2);
+				}
+
+				// Lambert hillshade on the world-scale gradient (1 px = 1 m, height ×251 m).
+				int xm = x > 0 ? x - 1 : x, xp = x < n - 1 ? x + 1 : x;
+				int ym = y > 0 ? y - 1 : y, yp = y < n - 1 ? y + 1 : y;
+				float gx = (_heightMap[xp, y] - _heightMap[xm, y]) * 251f / (xp - xm == 0 ? 1 : xp - xm);
+				float gy = (_heightMap[x, yp] - _heightMap[x, ym]) * 251f / (yp - ym == 0 ? 1 : yp - ym);
+				Vector3 nrm = new Vector3(-gx, -gy, 1f).Normalized();
+				float shade = Mathf.Clamp(nrm.Dot(light), 0f, 1f);
+
+				Color c = tint * (0.35f + 0.65f * shade);
+				c.A = 1f;
+				img.SetPixel(x, y, c);
+			}
+		}
+		Texture = ImageTexture.CreateFromImage(img);
+	}
+
 	/// <summary>
 	/// Paints the water-stage snapshot from the stage's own outputs (the biome grid
 	/// does not exist yet at this point in the pipeline): ocean deep blue, lakes a

Tools/Scripts/RoundTripHarness.cs

@@ -120,6 +120,7 @@ public partial class RoundTripHarness : Node
 		ok &= CompareRoads("Rugged", a.RuggedRoads, b.RuggedRoads);
 		ok &= CompareRoads("Trail", a.TrailRoads, b.TrailRoads);
 		ok &= CompareWater(a, b);
+		ok &= CompareTerrainCurve(a, b);
 
 		if (ok)
 			GD.Print($"[Harness] Semantic equality holds: {a.MapSize}x{a.MapSize} grid, " +
@@ -185,6 +186,29 @@ public partial class RoundTripHarness : Node
 		return ok;
 	}
 
+	private bool CompareTerrainCurve(WorldBlueprint a, WorldBlueprint b)
+	{
+		if (a.TerrainCurve == null && b.TerrainCurve == null)
+		{
+			GD.Print("[Harness] TCRV: absent in source — nothing to compare (and none reappeared).");
+			return true;
+		}
+		if (a.TerrainCurve == null || b.TerrainCurve == null)
+		{
+			GD.PrintErr("[Harness] TCRV presence mismatch between source and reread.");
+			return false;
+		}
+		var ca = a.TerrainCurve; var cb = b.TerrainCurve;
+		bool same = ca.Version == cb.Version;
+		float[] fa = { ca.T1, ca.T2, ca.T3, ca.T4, ca.HMaxCal, ca.Sea, ca.OrangeCeil, ca.RedCeil, ca.PlateauLo, ca.PlateauHi, ca.PeakCap, ca.TailSlope };
+		float[] fb = { cb.T1, cb.T2, cb.T3, cb.T4, cb.HMaxCal, cb.Sea, cb.OrangeCeil, cb.RedCeil, cb.PlateauLo, cb.PlateauHi, cb.PeakCap, cb.TailSlope };
+		for (int i = 0; i < fa.Length; i++)
+			if (System.BitConverter.SingleToInt32Bits(fa[i]) != System.BitConverter.SingleToInt32Bits(fb[i])) same = false;
+		if (!same) { GD.PrintErr("[Harness] TCRV fields differ."); return false; }
+		GD.Print($"[Harness] TCRV equal (curve v{ca.Version}).");
+		return true;
+	}
+
 	private bool CompareRoads(string tier, List<Vector2[]> a, List<Vector2[]> b)
 	{
 		if (a.Count != b.Count)