docs(issues): close #27 (cloud parity) — DONE-via-Fix-2

Cloud rendering parity with retail confirmed visually under Phase 0 of
the #27 fix plan: launched acdream with no DG override (LCG-picked
matches retail's pick), compared cloud coverage / color / edges /
movement at the same in-game time. User verdict: "Cloud and colors look
correct."

The original #27 observation from earlier in this session was a
side-effect of the broken `effEmissive=1.0` default that saturated every
sky mesh's vTint to white. That bug, plus the orthogonal `surface.Translucency`
plumbing gap, were both repaired in commit 4678b3e:
  - Fix 1 (Translucency): cloud surface 0x08000023 has Translucency=0.25,
    now plumbed end-to-end → clouds at 75% opacity instead of 100%.
  - Fix 2 (Luminosity): cloud surfaces have Luminosity=0.0, so post-fix
    they run through `vTint = ambient + sun·N·L` instead of saturating
    to white — clouds pick up the keyframe time-of-day tint.

User also flagged that acdream's clock is "a few minutes ahead" of retail
(sun higher on the horizon at the same wall-clock moment). That is the
existing #3 (`Client clock drifts from retail after ~10 minutes —
periodic TimeSync missing`), reproducing exactly as documented. Out of
scope for the sky-fixes branch.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/ISSUES.md

@@ -272,29 +272,6 @@ missing is the plugin-API surface.
 
 ---
 
-## #27 — Cloud meshes appear missing or faint compared to retail
-
-**Status:** OPEN
-**Severity:** LOW (aesthetic feature-parity — doesn't break gameplay)
-**Filed:** 2026-04-26
-**Component:** sky / clouds
-
-**Description:** After fixing Bug B (#26 — stars-as-square), the user observed during visual verification that cloud coverage in the sky doesn't match retail. Cloud meshes are authored in the dat (e.g. `0x010015B6`, `0x01004C35`-`0x01004C38`, `0x01004C36` etc) and `tools/StarsProbe` confirms they're loaded into the SkyObject lists with non-zero TexVelocity (so they get GL_REPEAT correctly under the post-#26 code path). They're not strictly missing — they're rendered — but their visual presence falls short of retail.
-
-**Root cause / status:** Unknown. Hypotheses: (a) cloud surfaces' alpha/blend mode is too subtle (cloud surface flags or shader path under-emphasise the texture); (b) cloud meshes positioned/scaled wrong relative to the dome so they're inside the dome and occluded; (c) DayGroup keyframe interpolation suppresses cloud transparency at certain times of day; (d) some cloud SkyObjects we should be rendering are filtered out by a Properties bit we mis-handle (Props=0x02 might mean something more than "cloud — render it"); (e) retail uses an additive cloud blend that our Translucency classifier doesn't apply.
-
-**Files:**
-- `src/AcDream.App/Rendering/Sky/SkyRenderer.cs` — sky pass; check per-cloud blend / luminosity / transparency.
-- `src/AcDream.Core/World/SkyDescLoader.cs` — Properties bit decoding.
-- `src/AcDream.App/Rendering/Shaders/sky.frag` — cloud transparency math.
-- `tools/StarsProbe/` — already dumps cloud GfxObj UVs + bounds; extend to dump per-DayGroup cloud surface flags.
-
-**Research:** None yet. `tools/StarsProbe` output already enumerates which DayGroups reference which cloud meshes — start there.
-
-**Acceptance:** Side-by-side launch of acdream and a retail client at the same `ACDREAM_DAY_GROUP` shows visually-comparable cloud coverage in the sky.
-
----
-
 ## #28 — Aurora ("northern lights") effect not rendered
 
 **Status:** OPEN
@@ -318,6 +295,14 @@ missing is the plugin-API surface.
 
 # Recently closed
 
+## #27 — [DONE 2026-04-26] Cloud meshes appeared missing or faint vs retail
+
+**Closed:** 2026-04-26
+**Commit:** `4678b3e fix(sky): apply per-Surface Translucency + Luminosity for retail-faithful weather`
+**Resolution:** Resolved as a side-effect of the Bug A fix. The original observation came from a session where every sky mesh got `effEmissive = 1.0` (saturated `vTint` to white), which made stars/clouds look full-bright instead of time-of-day-tinted. Fix 2 corrected the emissive default to `sub.SurfLuminosity` so cloud surfaces (Lum=0.0) now run through the ambient+diffuse vertex-lit path and pick up keyframe tint. Fix 1 separately plumbed `surface.Translucency` to the shader, picking up the 0.25 translucency on cloud surface `0x08000023` (75% opacity). Visual verification under Phase 0 of the followup plan: clouds and colors now match retail at LCG-picked DayGroups across the day cycle.
+
+---
+
 ## #1 — [DONE 2026-04-26] Rain falls only to horizon, not to the player's feet
 
 **Closed:** 2026-04-26