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feat(shafts): the spine joins its neighbours -- necessary, not sufficient

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Jahni chose: make the (0,0) column join the shafts it passes, so
VerticalShafts behaves like the other seven archetypes. Built, and it
works as far as it goes -- the spine is now the LARGEST air component in
13 of 16 seeds (share up to 0.81, was 0.096 and never largest).

⚠️ IT DOES NOT MEET THE ACCEPTANCE CRITERION. arrival->departure is still
1/16. Reported as a failure rather than dressed up, because the criterion
was the measured law, not "the code was written". The test now prints
ACCEPTANCE arrival->departure: FAIL (1/16 seeds pass) so it cannot be
quietly forgotten.

Why it is insufficient, and it is structural: the spine only joins its own
3x3 cell neighbourhood, while passage mouths land 60-200 voxels from
(0,0). The departure network is unreachable from the spine in all 16
seeds. Joining the hub to its neighbours does not help if the rest of the
graph never reaches the hub.

Part A diagnosis (seed 1337, margin 0, step 2, radius 192):
  baseline              30 components, largest .220
  roughness 0           17 components, largest .226
  connector radius 8    29 components, largest .229

H1 is real but partial: roughness fragments the space (13 of the 30
components are noise pockets), yet widening connectors past the proven
roughness bound barely moves it. So roughness is NOT what severs the
network -- the largest component sits at ~0.22 in every variant, which is
the signature of a graph below its percolation threshold. The lever is
topology, not radius. H2 (the hardcoded 1.6 pair cutoff) went untested.

Implementation notes: the spine is added ONLY as a connector endpoint, not
as a carving shaft -- VF_ApplyOriginSpine remains sole owner -- and is
excluded from ledge placement. Spine connectors use radius 6.625, above
the proven roughness supremum of 5.625 (sup|FBM| = 1.5, not 1.0).
SpineRadius is threaded through BuildVerticalShaftStack, not hardcoded.

Op-stack mirror bit-identical over 20,000 samples, 0 box-verdict
violations. LayoutOrderIndependence green.

Build clean, 19 succeeded / 0 warnings / 0 failed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Bp7FxoQcSoiuhxjuLr6aBM
This commit is contained in:
Fr0zkaandClaude Opus 5 committed 2026-08-30 16:52:57 +02:00
1 parent 5519b323c8
commit 58e61cdefa
5 files changed
+147 -40
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Source/VoxelForge/Private/VoxelGenerator.cpp
+31 -9
View File
@@ -3701,23 +3701,26 @@ float UVoxelGenerator::GetVerticalShaftDensity(float WorldX, float WorldY, float
// Shafts + cross-connectors of the 3×3 neighbourhood are pure functions of (cell, seed,
// params) yet were re-hashed PER VOXEL (9 cell rolls + a pair hash per shaft pair). Bake
// them once per centre cell (thread_local); per-voxel work = the cylinder/capsule SDFs.
struct FLocalShaft { float X, Y, R; };
struct FLocalConn { FVector A, B; };
thread_local TArray<FLocalShaft, TInlineAllocator<9>> Shafts;
thread_local TArray<FLocalConn, TInlineAllocator<8>> Conns;
struct FLocalShaft { float X, Y, R; bool bOriginSpine; };
struct FLocalConn { FVector A, B; float Radius; };
thread_local TArray<FLocalShaft, TInlineAllocator<10>> Shafts;
thread_local TArray<FLocalConn, TInlineAllocator<16>> Conns;
thread_local int32 VS_CX = INT32_MAX, VS_CY = INT32_MAX;
thread_local uint32 VS_Seed = 0xFFFFFFFFu;
thread_local float VS_Spacing = -1.0f, VS_Dens = -1.0f, VS_MinR = -1.0f, VS_MaxR = -1.0f,
VS_Cross = -1.0f, VS_BotZ = FLT_MAX, VS_TopZ = FLT_MAX;
VS_Cross = -1.0f, VS_ConnR = -1.0f, VS_Rough = -1.0f,
VS_SpineR = -1.0f, VS_BotZ = FLT_MAX, VS_TopZ = FLT_MAX;
if (CX != VS_CX || CY != VS_CY || S != VS_Seed || Spacing != VS_Spacing ||
Params.ShaftDensity != VS_Dens || Params.ShaftMinRadius != VS_MinR || Params.ShaftMaxRadius != VS_MaxR ||
Params.CrossConnectChance != VS_Cross ||
Params.CrossConnectChance != VS_Cross || Params.ConnectorRadius != VS_ConnR ||
Params.SurfaceRoughness != VS_Rough || OriginSpineRadius != VS_SpineR ||
Params.StrateBottomWorldZ != VS_BotZ || Params.StrateTopWorldZ != VS_TopZ)
{
VS_CX = CX; VS_CY = CY; VS_Seed = S; VS_Spacing = Spacing;
VS_Dens = Params.ShaftDensity; VS_MinR = Params.ShaftMinRadius; VS_MaxR = Params.ShaftMaxRadius;
VS_Cross = Params.CrossConnectChance;
VS_Cross = Params.CrossConnectChance; VS_ConnR = Params.ConnectorRadius;
VS_Rough = Params.SurfaceRoughness; VS_SpineR = OriginSpineRadius;
VS_BotZ = Params.StrateBottomWorldZ; VS_TopZ = Params.StrateTopWorldZ;
Shafts.Reset();
Conns.Reset();
@@ -3737,9 +3740,19 @@ float UVoxelGenerator::GetVerticalShaftDensity(float WorldX, float WorldY, float
Sh.Y = (ny + 0.15f + JY * 0.7f) * Spacing;
Sh.R = FMath::Lerp(Params.ShaftMinRadius, Params.ShaftMaxRadius,
VoxelHash::ToFloat01(VoxelHash::Mix(Hh ^ 0xBEEFu)));
Sh.bOriginSpine = false;
Shafts.Add(Sh);
}
// The structural (0,0) spine is not re-carved here. It participates only as a
// connector endpoint. The local 3x3 set is origin-adjacent when its centre cell is in
// the central 3x3; the structural post remains the sole owner of the vertical column.
const bool bOriginNearby = FMath::Abs(CX) <= 1 && FMath::Abs(CY) <= 1;
if (bOriginNearby && OriginSpineRadius > 0.0f)
{
Shafts.Add({0.0f, 0.0f, OriginSpineRadius, true});
}
// Horizontal connectors between nearby shaft pairs (hash-gated).
if (Params.CrossConnectChance > 0.0f && Shafts.Num() >= 2)
{
@@ -3750,6 +3763,7 @@ float UVoxelGenerator::GetVerticalShaftDensity(float WorldX, float WorldY, float
{
const FLocalShaft& A = Shafts[i];
const FLocalShaft& B = Shafts[j];
const bool bSpineConnector = A.bOriginSpine || B.bOriginSpine;
const float DSq = FMath::Square(A.X - B.X) + FMath::Square(A.Y - B.Y);
if (DSq > FMath::Square(Spacing * 1.6f)) continue; // only neighbours
@@ -3760,7 +3774,13 @@ float UVoxelGenerator::GetVerticalShaftDensity(float WorldX, float WorldY, float
if (VoxelHash::ToFloat01(PH) >= Params.CrossConnectChance) continue;
const float Zc = FMath::Lerp(BottomZ, TopZ, VoxelHash::ToFloat01(VoxelHash::Mix(PH)));
Conns.Add({ FVector(A.X, A.Y, Zc), FVector(B.X, B.Y, Zc) });
const float ConnectorR = bSpineConnector
? FMath::Max(
Params.ConnectorRadius,
FMath::Max(Params.SurfaceRoughness, 0.0f)
* VOXEL_NOISE_SCALE * 1.5f + 1.0f)
: Params.ConnectorRadius;
Conns.Add({ FVector(A.X, A.Y, Zc), FVector(B.X, B.Y, Zc), ConnectorR });
}
}
}
@@ -3770,13 +3790,14 @@ float UVoxelGenerator::GetVerticalShaftDensity(float WorldX, float WorldY, float
// Vertical shafts as infinite cylinders (boundary seal handles the ends).
for (const FLocalShaft& Sh : Shafts)
{
if (Sh.bOriginSpine) continue; // VF_ApplyOriginSpine owns the structural column.
const float DX = WorldX - Sh.X;
const float DY = WorldY - Sh.Y;
CaveSDF = FMath::Min(CaveSDF, FMath::Sqrt(DX * DX + DY * DY) - Sh.R);
}
for (const FLocalConn& C : Conns)
{
CaveSDF = FMath::Min(CaveSDF, VoxelSDF::Capsule(Pos, C.A, C.B, Params.ConnectorRadius));
CaveSDF = FMath::Min(CaveSDF, VoxelSDF::Capsule(Pos, C.A, C.B, C.Radius));
}
// Wall roughness.
@@ -3807,6 +3828,7 @@ float UVoxelGenerator::GetVerticalShaftDensity(float WorldX, float WorldY, float
const FLocalShaft* Near = nullptr; float BestSq = FLT_MAX;
for (const FLocalShaft& Sh : Shafts)
{
if (Sh.bOriginSpine) continue; // ledges belong to real shafts, not the post.
const float D2 = FMath::Square(WorldX - Sh.X) + FMath::Square(WorldY - Sh.Y);
if (D2 < BestSq) { BestSq = D2; Near = &Sh; }
}