islaApocalypse/Core/Scripts/BlueprintFormat.cs
beezm e7de292b3d 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>
2026-08-07 15:24:33 -04:00

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namespace IslaApocalypse.Core
{
/// <summary>
/// The single registry of constants for the v2 blueprint container — magic, version,
/// section tags, validation bounds, and the sentinel values used when a v2 file is
/// re-encoded from a v1 source that cannot supply real generation parameters.
///
/// The byte-accurate layout lives in Core/Scripts/BLUEPRINT_FORMAT.md. Writer:
/// BlueprintWriter.WriteV2. Reader: MapDataParser (v2 branch). Tags are FourCC codes
/// stored as little-endian u32, so the raw bytes on disk read as ASCII ("PRMS", "HGTS",
/// ...) in a hex dump.
/// </summary>
public static class BlueprintFormat
{
// "ISLA" as raw bytes 'I','S','L','A' == little-endian u32 0x414C5349.
// Deliberately NOT a length-prefixed .NET string: the v1 header starts with the
// 7-bit length prefix 0x07, so the first byte alone (0x49 vs 0x07) identifies the
// format and the reader can dispatch without ambiguity.
public const uint MAGIC = 0x414C5349;
public const uint VERSION = 2;
// Section tags (FourCC, little-endian). Reader rule: known tag -> parse,
// unknown tag -> skip by length and continue. Never reuse a retired tag value.
public const uint TAG_PARAMS = 0x534D5250; // "PRMS"
public const uint TAG_HEIGHTS = 0x53544748; // "HGTS"
public const uint TAG_BIOMES = 0x4D4F4942; // "BIOM"
public const uint TAG_TOWNS = 0x4E574F54; // "TOWN"
public const uint TAG_ROADS_HIGHWAY = 0x57484452; // "RDHW"
public const uint TAG_ROADS_BRANCH = 0x52424452; // "RDBR"
public const uint TAG_ROADS_RUGGED = 0x47524452; // "RDRG"
public const uint TAG_ROADS_TRAIL = 0x4C544452; // "RDTL"
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
// level can never encode to 0. Decodes back via (q 1) / 32768. Covers
// [0 .. ~1.99997] raw at 1/32768 raw resolution ≈ 7.7 mm of world height
// (1 raw unit = 251 m) — far below the 1 m voxel.
public const float WSRF_SCALE = 1f / 32768f;
public static ushort EncodeWaterLevel(float level)
{
return (ushort)Godot.Mathf.Clamp(1 + Godot.Mathf.RoundToInt(level * 32768f), 1, ushort.MaxValue);
}
public static float DecodeWaterLevel(ushort quantized)
{
return (quantized - 1) * WSRF_SCALE;
}
// MapSize sanity bounds, checked before any allocation on read.
public const int MIN_MAP_SIZE = 256;
public const int MAX_MAP_SIZE = 32768;
// Sentinels written into the params section when the source blueprint came from a
// v1 file (a re-encode cannot know the original generation inputs). WorldSeed 0 is
// also the config "randomize" sentinel, which no real resolved seed ever is.
public const int SENTINEL_WORLD_SEED = 0;
public const float SENTINEL_CRATER_RADIUS = -1f;
public const float SENTINEL_DENSITY_MULTIPLIER = -1f;
public const float SENTINEL_IMPACT_CENTER = -1f; // both components
/// <summary>Renders a tag as its 4 ASCII characters, for log messages.</summary>
public static string TagToString(uint tag)
{
return new string(new[] {
(char)(tag & 0xFF), (char)((tag >> 8) & 0xFF),
(char)((tag >> 16) & 0xFF), (char)((tag >> 24) & 0xFF)
});
}
}
}