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feat(core): procedural scenery from Region.SceneInfo (Phase 2c)

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Adds SceneryGenerator.Generate which walks Region.TerrainInfo.TerrainTypes
+ Region.SceneInfo.SceneTypes for each landblock vertex, selects a scene
using the AC client's pseudo-random LCG hash of global cell coordinates,
then rolls each ObjectDesc's frequency, computes a displaced cell-local
position, random scale, and random rotation — the exact algorithm
ACViewer ports from the retail AC client's get_land_scenes().

Phase 2 rendered 239 explicit Stab+Building entities on the 3x3 Holtburg
grid but was missing every procedurally-placed tree, bush, rock, fence,
and small decoration because these are not stored as LandBlockInfo entries.
This adds 419 scenery entities across the same 9 landblocks, bringing the
total to 658.

Integration in GameWindow.OnLoad: after the existing Stab/Building
hydration loop, iterate each landblock's scenery spawns, resolve each
to a GfxObj or Setup via the same mesh pipeline, bake the random scale
into each MeshRef's PartTransform so the static mesh renderer doesn't
need a scale field on WorldEntity, and sample the landblock heightmap
bilinearly for the ground Z (simpler than ACViewer's find_terrain_poly
slope-aware placement).

Deliberate deferrals for first pass:
- No slope-based rejection (obj.MinSlope/MaxSlope). Trees may end up on
  cliffs they shouldn't be on.
- No road-overlap rejection. Scenery may spawn in roads.
- No building-overlap rejection. Scenery may clip buildings.
- No WeenieObj handling (those are dynamic spawns, not static scenery).

All three filters will be added in a follow-up phase when we have the
walkable-polygon infrastructure they need.

Build clean, 48 tests still pass, smoke verified: "scenery: spawned 419
entities across 9 landblocks", process runs without exceptions.

Addresses the user visual feedback after Phase 2b: "some extra details
are missing, like a tree and the statue on top of the foundry". The tree
issue is now fixed (419 trees/bushes/rocks/etc placed). The foundry
statue may still be missing if it's a hierarchical Setup part (Phase 2a's
SetupMesh.Flatten intentionally doesn't walk ParentIndex) — that's a
separate fix if smoke verification shows it's still missing.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This commit is contained in:
Erik 2026-04-10 21:07:12 +02:00
parent fe0bfb075b
commit 9970811dc3
2 changed files with 306 additions and 1 deletions
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194
src/AcDream.Core/World/SceneryGenerator.cs Normal file
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using System.Numerics;
using DatReaderWriter;
using DatReaderWriter.DBObjs;
using DatReaderWriter.Types;
namespace AcDream.Core.World;
/// <summary>
/// Procedural scenery placement for a landblock. AC encodes "sparse decoration"
/// (trees, bushes, rocks, fences, small props) NOT as explicit Stab entries on
/// the LandBlockInfo but as per-terrain-vertex Scene/ObjectDesc references in
/// the Region dat, placed pseudo-randomly via deterministic LCG math keyed on
/// the vertex's global cell coordinates. Without this generator, any landblock
/// rendered from dats is missing all of its natural scenery.
///
/// Algorithm ported from ACViewer's Physics/Common/Landblock.get_land_scenes()
/// which is itself a port of the original AC client's scenery walker. We
/// deliberately skip the slope/road/building-overlap checks the original does;
/// those prevent scenery from floating in roads or clipping buildings but
/// require walkable-polygon lookups that we don't yet have. Accepting visual
/// artifacts (trees inside roads, scenery clipping buildings) for a first pass
/// and deferring the filters to a later phase.
/// </summary>
public static class SceneryGenerator
{
// AC landblock geometry — matches LandblockMesh.
private const int VerticesPerSide = 9;
private const float CellSize = 24.0f;
private const float LandblockSize = 192.0f; // 8 cells * 24 units
public readonly record struct ScenerySpawn(
uint ObjectId, // GfxObj or Setup id
Vector3 LocalPosition, // landblock-local world units
Quaternion Rotation,
float Scale);
/// <summary>
/// Generate all scenery entries for one landblock. Uses the bit-packed
/// TerrainInfo Type (bits 2-6) and Scenery (bits 11-15) fields to index into
/// Region.TerrainInfo.TerrainTypes[type].SceneTypes[scenery] → a SceneInfo
/// index into Region.SceneInfo.SceneTypes[sceneInfo].Scenes. Each cell picks
/// one scene via a pseudo-random hash of the cell's global coordinates, then
/// iterates the scene's ObjectDesc entries with per-object frequency rolls.
/// </summary>
public static IReadOnlyList<ScenerySpawn> Generate(
DatCollection dats,
Region region,
LandBlock block,
uint landblockId)
{
var result = new List<ScenerySpawn>();
if (region.TerrainInfo?.TerrainTypes is null || region.SceneInfo?.SceneTypes is null)
return result;
uint blockX = (landblockId >> 24) * 8; // 8 cells per landblock
uint blockY = ((landblockId >> 16) & 0xFFu) * 8;
// The original iterates Terrain[0..80] — 81 vertices of a 9x9 grid.
// The heightmap is packed x-major (Height[x*9+y]), so we match that here.
for (int x = 0; x < VerticesPerSide; x++)
{
for (int y = 0; y < VerticesPerSide; y++)
{
int i = x * VerticesPerSide + y;
ushort raw = block.Terrain[i];
uint terrainType = (uint)((raw >> 2) & 0x1F); // bits 2-6
uint sceneType = (uint)((raw >> 11) & 0x1F); // bits 11-15
if (terrainType >= region.TerrainInfo.TerrainTypes.Count) continue;
var sceneTypeList = region.TerrainInfo.TerrainTypes[(int)terrainType].SceneTypes;
if (sceneType >= sceneTypeList.Count) continue;
uint sceneInfo = sceneTypeList[(int)sceneType];
if (sceneInfo >= region.SceneInfo.SceneTypes.Count) continue;
var scenes = region.SceneInfo.SceneTypes[(int)sceneInfo].Scenes;
if (scenes.Count == 0) continue;
uint cellX = (uint)x;
uint cellY = (uint)y;
uint globalCellX = cellX + blockX;
uint globalCellY = cellY + blockY;
// Scene-selection hash: picks one scene from the terrain's scene list.
uint cellMat = globalCellY * (712977289u * globalCellX + 1813693831u)
- 1109124029u * globalCellX + 2139937281u;
double offset = cellMat * 2.3283064e-10;
int sceneIdx = (int)(scenes.Count * offset);
if (sceneIdx >= scenes.Count || sceneIdx < 0) sceneIdx = 0;
uint sceneId = (uint)scenes[sceneIdx];
var scene = dats.Get<Scene>(sceneId);
if (scene is null) continue;
// Per-object hashes: roll frequency, compute displacement, scale, rotation.
uint cellXMat = unchecked(0u - 1109124029u * globalCellX);
uint cellYMat = 1813693831u * globalCellY;
uint cellMat2 = 1360117743u * globalCellX * globalCellY + 1888038839u;
for (uint j = 0; j < scene.Objects.Count; j++)
{
var obj = scene.Objects[(int)j];
if (obj.WeenieObj != 0) continue; // Weenie entries are dynamic spawns, not static scenery
double noise = unchecked((uint)(cellXMat + cellYMat - cellMat2 * (23399u + j))) * 2.3283064e-10;
if (noise >= obj.Frequency) continue;
// Displacement: pseudo-random offset within the cell.
var localPos = DisplaceObject(obj, globalCellX, globalCellY, j);
float lx = cellX * CellSize + localPos.X;
float ly = cellY * CellSize + localPos.Y;
if (lx < 0 || ly < 0 || lx >= LandblockSize || ly >= LandblockSize)
continue;
// Z at the cell corner from the heightmap. Skipping slope-based
// Z placement (ACViewer uses find_terrain_poly which we don't have)
// — accept that some scenery will float or clip.
float lz = 0f; // will be lifted to ground at render time via landblock heightmap
// Rotation
Quaternion rotation = Quaternion.Identity;
if (obj.MaxRotation > 0)
{
double rotNoise = unchecked((uint)(1813693831u * globalCellY
- (j + 63127u) * (1360117743u * globalCellY * globalCellX + 1888038839u)
- 1109124029u * globalCellX)) * 2.3283064e-10;
float degrees = (float)(rotNoise * obj.MaxRotation);
float radians = degrees * MathF.PI / 180f;
rotation = Quaternion.CreateFromAxisAngle(Vector3.UnitZ, radians);
}
// Scale
float scale;
if (obj.MinScale == obj.MaxScale)
{
scale = obj.MaxScale;
}
else
{
double scaleNoise = unchecked((uint)(1813693831u * globalCellY
- (j + 32593u) * (1360117743u * globalCellY * globalCellX + 1888038839u)
- 1109124029u * globalCellX)) * 2.3283064e-10;
scale = (float)(Math.Pow(obj.MaxScale / obj.MinScale, scaleNoise) * obj.MinScale);
}
if (scale <= 0) scale = 1f;
result.Add(new ScenerySpawn(
ObjectId: obj.ObjectId,
LocalPosition: new Vector3(lx, ly, lz),
Rotation: rotation,
Scale: scale));
}
}
}
return result;
}
/// <summary>
/// Pseudo-random displacement within a cell for a scenery object. Returns a
/// Vector3 in local cell-offset space (the caller adds it to the cell corner
/// to get landblock-local position).
/// </summary>
private static Vector3 DisplaceObject(ObjectDesc obj, uint ix, uint iy, uint iq)
{
float x, y;
var baseLoc = obj.BaseLoc.Origin;
if (obj.DisplaceX <= 0)
x = baseLoc.X;
else
x = (float)(unchecked((uint)(1813693831u * iy - (iq + 45773u) * (1360117743u * iy * ix + 1888038839u) - 1109124029u * ix))
* 2.3283064e-10 * obj.DisplaceX + baseLoc.X);
if (obj.DisplaceY <= 0)
y = baseLoc.Y;
else
y = (float)(unchecked((uint)(1813693831u * iy - (iq + 72719u) * (1360117743u * iy * ix + 1888038839u) - 1109124029u * ix))
* 2.3283064e-10 * obj.DisplaceY + baseLoc.Y);
float z = baseLoc.Z;
double quadrant = unchecked((uint)(1813693831u * iy - ix * (1870387557u * iy + 1109124029u) - 402451965u)) * 2.3283064e-10;
if (quadrant >= 0.75) return new Vector3(y, -x, z);
if (quadrant >= 0.5) return new Vector3(-x, -y, z);
if (quadrant >= 0.25) return new Vector3(-y, x, z);
return new Vector3(x, y, z);
}
}