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The whole "indoor interiors read dark/flat vs retail" saga was ONE root-cause bug: EnvCellRenderer.GetCellLightSet derived the landblock key as `cellId & 0xFFFF0000` (0xXXYY0000), but landblocks are keyed by the streaming id 0xXXYYFFFF. The lookup missed for EVERY cell, so SelectForObject never ran and every EnvCell wall received ZERO point lights — torches, lanterns, the viewer light, all of it. Confirmed by a [cell-light] probe: inBounds=False selected=0 across 1M+ cell draws; after the fix inBounds=True selected=3-4. User-confirmed the interiors now look like retail. Three faithful additions that were blocked by the key bug (and only show now): - Viewer light (LightManager.UpdateViewerLight): retail's SmartBox::set_viewer (0x00452c40) adds a white fill light at the player every frame via add_dynamic_light — the dominant interior fill (no sun indoors). acdream had NO dynamic lights at all. Params from the cdb capture: intensity 2.25, falloff 10, white, offset (0,0,2). Indoor-only via the AP-43 gate. - Weenie fixture lights (OnLiveEntitySpawnedLocked): server-spawned lanterns/ braziers carry Setup.Lights but the dat-static registration never saw CreateObject entities. Register on spawn; unregister on despawn (UnregisterOwner made unconditional). Register row AP-44. - IndoorObjectReceivesTorches now excludes the 0xFFFF landblock marker (it is not an EnvCell) — fixes WbDrawDispatcherIndoorFlagTests.LandblockId_OutdoorFlag0 (a #142 verification miss). Divergence register: AP-44 (weenie light spawn-position, no movement tracking), AP-47 (acdream's 128-light/camera-independent cap keeps interiors always-lit vs retail's 40-nearest-to-player budget that pops in on approach — intentional, user-preferred). Investigation: docs/research/2026-06-20-indoor-torch-lantern-lighting-investigation.md Core 1505 / App 476 green. Visual gate: user-confirmed "looks like retail now." Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
75 lines
4.9 KiB
Markdown
75 lines
4.9 KiB
Markdown
# A7 indoor torch/lantern lighting — why acdream interiors read dark (investigation)
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**Date:** 2026-06-20 **Mode:** report-only investigation (no code changed)
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**Trigger:** after #142 sun-gate (`ef5049f`) the Agent of Arcanum interior
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(`0xA9B40171/0172`) still reads dark; user: "retail uses torches **and lanterns**
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for lighting indoors."
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## Retail oracle — the static-light bake (decomp, confirmed)
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`SetStaticLightingVertexColors` (0x0059cfe0), per EnvCell mesh, per vertex:
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```
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for each vertex V:
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acc = (0,0,0) // from BLACK; no ambient/sun here
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for i in 0 .. world_lights.num_static_lights: // ALL lights — NO per-vertex/cell cap
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L = sorted_static_lights[i]
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if L.type==0: calc_point_light(V, acc, L) // 0x0059c8b0
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else: acc += dot(N,dir)*scale*L.color
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acc = clamp(acc, 0, 1) // per-channel, AFTER summing all
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V.diffuse = encode(acc)
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```
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`calc_point_light` (0x0059c8b0): `range = falloff × static_light_factor(1.3)`;
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back-face/range gated; `angular = dot_n/dist` (<1 m) else `dot_n/(dist²·dist)`;
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`scale = angular·(1−dist/range)·intensity`; per-channel cap `min(scale·c, c)`.
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**Global cap:** `max_static_lights = 0x28 = 40` (`insert_light` 0x0054d1b0 keeps a
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distance-sorted, replace-farthest list). So the bake sees up to **40 nearest static
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lights — and sums ALL of them per vertex.** There is no 8-light cap on the static
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wall bake. (The 8-light cap is the D3D *hardware* path for *dynamic objects*,
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`minimize_object_lighting` 0x0054d480 — a different path.)
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## acdream's torch path — three real divergences
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| # | Divergence | Site | Effect |
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|---|---|---|---|
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| Bug A | **Weenie fixture lights never registered.** `RegisterOwnedLight` is called ONLY from `ApplyLoadedTerrainLocked` for dat-baked landblock + EnvCell statics (Setup `0x02xxxxxx`, `Lights.Count>0`). Server `CreateObject` weenies (`OnLiveEntitySpawnedLocked`) never register lights. | `GameWindow.cs:6733-6758` (registers); `GameWindow.cs:2696/3275` (weenie path — no register) | If a lantern/torch is a server weenie, its light is **entirely absent**. |
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| Bug B | **Per-cell 8-light cap.** `GetCellLightSet`→`SelectForObject` keeps the **8 nearest-to-cell-center** lights (`MaxLightsPerObject=8`); 9th+ dropped. Retail sums up to 40. | `EnvCellRenderer.cs:1044`; `LightManager.cs:234-278` | Dense cells (dungeon corridors, fixture clusters) lose lights. **Not binding** for the Arcanum (only ~3 in range). |
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| Bug C | **128 global camera pre-filter.** `BuildPointLightSnapshot` keeps the 128 nearest-**to-camera** lights (`MaxGlobalLights=128`), drops the rest before per-cell selection. Retail has no global per-frame cap on statics. | `LightManager.cs:179,208-211` | `registeredLights=129` ⇒ already at the cap; drops farthest-from-camera. Hurts far lights, not the near interior. |
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Bug A·partial: the per-vertex bake is also approximated as **one 8-light set per
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whole cell** (uniform across all the cell's vertices), vs retail's true per-vertex
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bake — a fidelity gap (bright cluster smears across the cell), secondary to the
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source-count gaps above.
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The per-light shader formula (`pointContribution`) + the `min(pointAcc,1.0)` torch
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clamp **match** retail's `calc_point_light` + final saturate — magnitude per light
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is faithful. The gap is **missing / capped light SOURCES**, not per-light math.
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## Ranked hypotheses (for the Agent of Arcanum specifically)
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1. **H1 — the lanterns are server weenies ⇒ Bug A drops their light** (best fit
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for the "lanterns" hint). The cell shows only ~3 *dat* torches; lanterns absent.
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*Falsify:* pick a lantern in-game — guid `0x80…`/`0x7…` = weenie ⇒ confirmed.
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2. **H4 — per-cell (not per-vertex) bake / magnitude** — if the Arcanum has no
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weenie fixtures, the 3 dat torches are all there is and the per-cell-uniform bake
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under-fills vs retail's per-vertex bake.
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3. **H2/H3 (8-cap / 128-cap)** — real retail divergences, but **not binding** for
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this building (≤3 lights in range, near camera). They matter for dense dungeons.
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## Fix plan (faithful, per hypothesis)
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- **H1 (likely):** register `Setup.Lights` for light-bearing weenies in
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`OnLiveEntitySpawnedLocked`, mirroring `ApplyLoadedTerrainLocked:6742-6758`
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(guard `setup.Lights.Count>0`); unregister on despawn (`UnregisterByOwner`).
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Faithful: retail registers object lights regardless of static/dynamic origin.
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- **H2:** raise the per-cell static bake cap from 8 toward retail's 40 (the cap is
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retail-correct only for the *dynamic-object hardware* path, not the wall bake).
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- **H3:** make the per-cell selection independent of the 128 camera pre-filter for
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statics (retail's bake has no global count cap).
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- **H4:** move the cell bake toward per-vertex (longer-horizon A7 LightBake work).
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## What this is NOT
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NOT a #142 sun-gate regression and NOT an ambient bug (ambient matches retail;
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it's just dim rainy-twilight). It is missing / capped light **sources**.
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