diag: ACDREAM_PROBE_LIGHT — log dungeon ambient/sun/active-light state (#133 A7)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/AcDream.App/Rendering/GameWindow.cs

@@ -7625,6 +7625,24 @@ public sealed class GameWindow : IDisposable
 
             _sceneLightingUbo?.Upload(ubo);
 
+            // #133 A7 (2026-06-13): objective dungeon-lighting probe. One
+            // rate-limited [light] line — insideCell / ambient / sun /
+            // registered-point-lights / active-slot-count / player cell — so
+            // the dungeon-dim question is self-verifiable from launch.log
+            // without a screenshot. RegisteredCount is point/spot lights only
+            // (the sun lives in LightManager.Sun, never in the _all list);
+            // ubo.CellAmbient.W is the shader active-slot count, which counts
+            // the (zeroed) sun slot indoors. Inert unless ACDREAM_PROBE_LIGHT=1.
+            AcDream.Core.Rendering.RenderingDiagnostics.EmitLight(
+                insideCell:        playerInsideCell,
+                ambientR:          Lighting.CurrentAmbient.AmbientColor.X,
+                ambientG:          Lighting.CurrentAmbient.AmbientColor.Y,
+                ambientB:          Lighting.CurrentAmbient.AmbientColor.Z,
+                sunIntensity:      Lighting.Sun?.Intensity ?? 0f,
+                registeredLights:  Lighting.RegisteredCount,
+                activeLights:      (int)ubo.CellAmbient.W,
+                playerCellId:      playerRoot?.CellId ?? 0u);
+
             // Never cull the landblock the player is currently on.
             uint? playerLb = null;
             if (_playerMode && _playerController is not null)

src/AcDream.Core/Rendering/RenderingDiagnostics.cs

@@ -243,6 +243,34 @@ public static class RenderingDiagnostics
     public static bool ProbePhantomEnabled { get; set; } =
         Environment.GetEnvironmentVariable("ACDREAM_PROBE_PHANTOM") == "1";
 
+    /// <summary>
+    /// #133 A7 (2026-06-13) dungeon-lighting objective probe. When true,
+    /// the per-frame scene-lighting build emits ONE <c>[light]</c> line
+    /// roughly every second (wall-clock rate-limited like WB-DIAG) via
+    /// <see cref="EmitLight"/>:
+    /// <code>
+    /// [light] insideCell=&lt;bool&gt; ambient=(r,g,b) sun=&lt;intensity&gt;
+    ///         registeredLights=&lt;N&gt; activeLights=&lt;uCellAmbient.w&gt; playerCell=0x&lt;id&gt;
+    /// </code>
+    /// This is the self-verification signal for the dungeon-dim question:
+    /// <list type="bullet">
+    ///   <item><description><c>insideCell=true ambient=(0.20,0.20,0.20) sun=0</c>
+    ///   confirms the indoor branch fired (retail flat ambient, sun killed).</description></item>
+    ///   <item><description><c>registeredLights</c> is the count of dat-baked
+    ///   point/spot lights (<c>Setup.Lights</c>) registered with the
+    ///   <c>LightManager</c> — if this is 0 in a dungeon, the cell's static
+    ///   objects carry no baked torches (so the only illumination IS the
+    ///   0.2 ambient → dim).</description></item>
+    ///   <item><description><c>activeLights</c> is <c>uCellAmbient.w</c> — the
+    ///   shader's active-slot count, which INCLUDES the (zeroed) sun slot
+    ///   indoors. So <c>activeLights=1 registeredLights=0</c> = "only the dead
+    ///   sun slot, no torches in range".</description></item>
+    /// </list>
+    /// Output-only, inert when off. Initial state from <c>ACDREAM_PROBE_LIGHT=1</c>.
+    /// </summary>
+    public static bool ProbeLightEnabled { get; set; } =
+        Environment.GetEnvironmentVariable("ACDREAM_PROBE_LIGHT") == "1";
+
     // Cell-change gate for EmitVis. The probe fires once per distinct root cell
     // so launch.log stays readable under motion (the per-frame call is a no-op
     // when the root is unchanged). Sentinel 0 = "no root yet" — the first real
@@ -336,6 +364,50 @@ public static class RenderingDiagnostics
     /// </summary>
     internal static void ResetVisibilityProbeForTests() => _lastVisRootCellId = 0;
 
+    // Wall-clock rate-limit gate for EmitLight. Ticks (100 ns) is plenty —
+    // we only need ~1 Hz and avoid a Stopwatch allocation/field. Sentinel 0
+    // = "never emitted" so the first call always fires.
+    private static long _lastLightEmitTicks;
+    private const long LightEmitIntervalTicks = 10_000_000; // 1 s in 100-ns ticks
+
+    /// <summary>
+    /// #133 A7 — emit ONE rate-limited <c>[light]</c> line describing the
+    /// current scene-lighting state. Cheap no-op when
+    /// <see cref="ProbeLightEnabled"/> is false; otherwise fires at most
+    /// once per second. Pull the values from the spot where
+    /// <c>GameWindow.UpdateSunFromSky</c> set <c>Lighting.CurrentAmbient</c>
+    /// / <c>Lighting.Sun</c> and where <c>SceneLightingUbo.Build</c> computed
+    /// the active-slot count.
+    /// </summary>
+    /// <param name="insideCell">The <c>playerInsideCell</c> value driving the indoor branch.</param>
+    /// <param name="ambientR">Cell ambient red (xyz of <c>uCellAmbient</c>).</param>
+    /// <param name="ambientG">Cell ambient green.</param>
+    /// <param name="ambientB">Cell ambient blue.</param>
+    /// <param name="sunIntensity">The sun <c>LightSource.Intensity</c> (0 indoors).</param>
+    /// <param name="registeredLights">Total point/spot lights registered with the LightManager.</param>
+    /// <param name="activeLights"><c>uCellAmbient.w</c> — shader active-slot count (includes the zeroed sun slot indoors).</param>
+    /// <param name="playerCellId">The player's current cell id (0 if unresolved → outside).</param>
+    public static void EmitLight(bool insideCell,
+                                 float ambientR, float ambientG, float ambientB,
+                                 float sunIntensity,
+                                 int registeredLights,
+                                 int activeLights,
+                                 uint playerCellId)
+    {
+        if (!ProbeLightEnabled) return;
+
+        long now = DateTime.UtcNow.Ticks;
+        if (_lastLightEmitTicks != 0 && (now - _lastLightEmitTicks) < LightEmitIntervalTicks)
+            return;
+        _lastLightEmitTicks = now;
+
+        var ci = System.Globalization.CultureInfo.InvariantCulture;
+        Console.WriteLine(string.Format(ci,
+            "[light] insideCell={0} ambient=({1:0.###},{2:0.###},{3:0.###}) sun={4:0.###} registeredLights={5} activeLights={6} playerCell=0x{7:X8}",
+            insideCell, ambientR, ambientG, ambientB, sunIntensity,
+            registeredLights, activeLights, playerCellId));
+    }
+
     private static bool _probeEnvCellEnabled =
         Environment.GetEnvironmentVariable("ACDREAM_PROBE_ENVCELL") == "1";