fix(render): kill blown highlights + phantom doors (GPU-verified)

First GPU pass on the rev-3 depth pipeline surfaced two issues; both fixed
and re-rendered clean:

1. Blown near-field highlights (regression from 018909b). Mapping the
   nearest pixel to pure white (nearPlane=nearRaw) made the depth
   ControlNet render overexposed near floors/ceilings at strength 0.85.
   fpv.js: nearPlane=0 (anchor white at the camera; nearest real surface
   ≈gray 214, headroom intact) + minSpan 5→8. Re-bake confirms the blown
   ceiling is gone while recesses still reach black and geometry holds.

2. Phantom doors on closed walls — a PROMPT problem, not the depth map
   (present in old maps too). Opening NOUNS in the positive prompt summon
   a passage onto solid stone: threshold's "gatehouse, portcullis,
   entrance" painted a gate on a blank wall, and at cfg 1.0 the negative
   can't cancel it. bake_atlas.py: THEME_BODY_CLOSED (full theme flavor,
   zero opening nouns) for closed facings + opening-nouns negated on
   closed facings only. r0_N (threshold) now renders clean ashlar wall.
   ("Bricked-up archway" backfires — "archway" alone re-summons the arch.)

Also: sweep_strength.py re-exec-under-venv guard (the venv python is a
symlink to the base interpreter, so the realpath check wrongly skipped
the hop and the montage died after every render); now env-sentinel
guarded. Findings in .dev/2026-06-15-diffusion-pipeline-reliability.md.

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

.dev/2026-06-15-diffusion-pipeline-reliability.md

@@ -59,6 +59,38 @@ With a weak signal you crank strength to force adherence; a strong signal wants
 3. Then re-bake a full atlas at the chosen strength and spot-check a montage vs the
    old `acc8137`/`a12bcbb` bakes.
 
+## Iteration 3 — first GPU pass (2026-06-15/16, workstation back up)
+
+Ran the A/B + strength sweep (16 renders) and follow-ups. Findings:
+
+1. **Open frames: the rev-3 normalization works.** `r8_N` renders a clean pillared
+   hall with the passage landing exactly on the depth's black recess. NEW ≈ OLD here
+   only because `r8_N` already had structure; the win shows on small-room recesses.
+2. **Blown-highlight regression (introduced by rev-3, now FIXED).** Mapping the
+   nearest pixel to pure white (`nearPlane = nearRaw`) made the ControlNet render
+   overexposed near floors/ceilings at strength 0.85. Fix: `nearPlane = 0` (anchor
+   white at the camera, nearest real surface ≈ gray 214) + `minSpan = 8`. Re-baked +
+   re-rendered: blown ceiling gone, geometry adherence intact, recesses still black.
+3. **Phantom doors on closed walls = a PROMPT problem, not depth.** Present in OLD
+   maps too. Root cause: opening-NOUNS in the positive prompt. `threshold`'s body
+   ("dungeon gatehouse, iron portcullis, entrance") painted a gate onto a solid
+   wall; at cfg 1.0 the negative can't cancel it. A generic opening-free body
+   ("rough-hewn stone chamber, bare granite walls") renders a clean dead-end.
+   "Bricked-up archway" BACKFIRES — "archway" alone re-summons the arch.
+   → Fix in `bake_atlas.py`: `THEME_BODY_CLOSED` (theme flavor, zero opening nouns)
+   for closed facings + opening-nouns added to the negative on closed facings only.
+
+**Tooling fixes:** `sweep_strength.py` re-exec-under-venv guard (the venv's python is
+a symlink to the base interpreter, so the realpath check wrongly skipped the hop —
+now an env-sentinel guard); montage now succeeds in one invocation.
+
+### Still open after iteration 3
+- **Pick the production strength.** Sweep rendered 0.55/0.7/0.85/1.0; 0.85 looks good
+  on open frames now. Eyeball the full montage for the lowest strength that still
+  honors geometry (lower = more natural texture). Then set `bake_atlas.py --strength`.
+- **Re-bake a full atlas** (seed 7) with rev-3 maps + closed-body prompts and montage
+  vs the old `a12bcbb` bake to confirm the end-to-end win across all themes.
+
 ## Open levers if still hit-and-miss after strength tuning
 - `nearPlane`/`minSpan`/`gamma` are now tunable per-export — A/B if near surfaces
   read too blown-out (the AFTER maps are ~47% near-white; may want a slightly

reikhelm-web/fpv.js

@@ -186,14 +186,20 @@ export function computeFPVDepth(env, opts = {}) {
     if (x === centerX) ahead = dist;
   }
 
-  // Per-frame normalization window. The far plane tracks the deepest surface
-  // actually visible (so a real passage reads black), but is clamped to a floor
-  // (minSpan) so a shallow dead-end nook isn't stretched into a dramatic fake
-  // tunnel — its faced wall stays an honest mid-gray slab, not a black recess
-  // the model would paint a phantom door into. `gamma` then shapes the falloff
-  // within that window.
-  const nearPlane = opts.nearPlane ?? nearRaw;
-  const minSpan = opts.minSpan ?? 5;
+  // Per-frame normalization window.
+  //   nearPlane = 0 (the camera), NOT the nearest surface: a GPU sweep showed
+  //     that mapping the closest pixel to pure white (255) made the depth
+  //     ControlNet render blown-out, overexposed near floors/ceilings. Anchoring
+  //     white at the camera leaves the nearest real surface (~1 cell) at ~gray
+  //     214 — bright, but with headroom — which renders as lit stone, not glare.
+  //   farPlane tracks the deepest surface actually visible so a real passage
+  //     reads black, but is floored (minSpan) so a shallow dead-end isn't
+  //     stretched into a fake tunnel — its faced wall stays a brighter mid-gray
+  //     slab. (Phantom doors on fully-closed walls are a separate camera-vantage
+  //     problem, not a normalization one — the faced wall is unavoidably darker
+  //     than the near floor; see the .dev reliability note.)
+  const nearPlane = opts.nearPlane ?? 0;
+  const minSpan = opts.minSpan ?? 8;
   const farPlane = clamp(farRaw, nearPlane + minSpan, maxView);
   const span = Math.max(farPlane - nearPlane, 1e-3);
 

tools/bake_atlas.py

@@ -53,21 +53,48 @@ THEME_BODY = {
     "stone":     "rough-hewn stone chamber, bare granite walls, plain and ancient",
 }
 DEFAULT_BODY = THEME_BODY["stone"]
+# Closed-facing bodies: SAME theme flavor (material, contents, mood) but every
+# architectural OPENING noun stripped — gatehouse/portcullis/entrance, wall
+# niches, the throne's recessed dais, etc. A GPU sweep (2026-06-15) proved the
+# phantom doors on closed walls were summoned by these words, not the depth map:
+# `threshold`'s "gatehouse, portcullis, entrance" painted a gate onto a solid
+# wall, and at cfg 1.0 the negative branch is too weak to cancel it. Working WITH
+# a generic solid-wall description (no opening nouns) renders a clean dead-end;
+# even "bricked-up archway" backfires because "archway" alone re-summons the arch.
+THEME_BODY_CLOSED = {
+    "forge":     "forge chamber, soot-blackened granite walls, iron anvils and hanging chains, dim fiery glow",
+    "cistern":   "flooded cistern, dark still water, dripping wet stone walls, cold teal light",
+    "crypt":     "ancient crypt, carved stone sarcophagi along blank stone walls, cobwebs, cold pale light",
+    "library":   "ruined library, tall stone shelves of rotting books against the wall, drifting dust, warm dim light",
+    "throne":    "throne hall, towering carved stone columns and a blank stone wall, tattered banners, cold grandeur",
+    "vault":     "treasure vault, iron-bound chests and stone strongboxes against heavy locked stone walls, scattered gold",
+    "hall":      "grand pillared hall, carved stone columns and a high blank stone wall, vaulted ceiling",
+    "den":       "foul beast den, gnawed bones and filth, claw-scratched blank stone walls, dim red light",
+    "threshold": "heavy sealed gateroom of dungeon stone, worn flagstones, blank ashlar walls",
+    "stone":     "rough-hewn stone chamber, bare granite walls, plain and ancient",
+}
 # These reinforce the depth (a deep recess vs a near wall straight ahead) so the
 # model paints a passage only where one actually exists — killing phantom doors.
 AHEAD_OPEN = "a dark arched passage leads onward into shadow ahead"
 # cfg 1.0 makes negatives inert, so the closed case is carried by emphatic
-# positive description — themes like the vault say "locked", which otherwise
-# summons phantom doors on blank walls.
-AHEAD_WALL = ("the way ahead ends at a blank unbroken wall of carved stone blocks, "
-              "sealed solid masonry with no door and no opening, a dead end")
+# positive description (opening-free body above) + this sealed-wall clause.
+AHEAD_WALL = ("the way ahead ends at a blank unbroken wall of solid carved stone blocks, "
+              "sealed flat masonry, a dead end")
 NEGATIVE = ("person, people, human, figure, character, hands, fingers, hand, arm, arms, "
             "holding weapon, sword, feet, legs, body, silhouette, UI, HUD, text, watermark, modern")
+# Closed facings additionally negate every opening noun (cheap insurance; the
+# opening-free positive body does the real work). NOT applied to open facings —
+# they WANT a passage.
+NEG_OPENINGS = "doorway, door, archway, arch, opening, passage, tunnel, gate, portcullis, gateway, entrance, corridor"
 
 
 def prompt_for(theme, is_open):
+    """Return (positive, negative) for this (theme, facing)."""
+    if is_open:
         body = THEME_BODY.get(theme or "stone", DEFAULT_BODY)
-    return f"{STYLE}{body}, {AHEAD_OPEN if is_open else AHEAD_WALL}"
+        return f"{STYLE}{body}, {AHEAD_OPEN}", NEGATIVE
+    body = THEME_BODY_CLOSED.get(theme or "stone", THEME_BODY_CLOSED["stone"])
+    return f"{STYLE}{body}, {AHEAD_WALL}", f"{NEGATIVE}, {NEG_OPENINGS}"
 
 NAME_RE = re.compile(r"^r(\d+)_([NESW])_depth\.png$")
 
@@ -127,7 +154,7 @@ def main():
         room = rooms.get(int(rid), {})
         theme = room.get("theme")
         is_open = bool(room.get("open", {}).get(d, False))
-        prompt = prompt_for(theme, is_open)
+        prompt, negative = prompt_for(theme, is_open)
         strength = a.strength
         # Walls render under their own FIXED seed: the open-frame seed's
         # favorite composition is a centered doorway — exactly what a closed
@@ -140,7 +167,7 @@ def main():
         if not run(["python3", COMFY, "zrender", a.url, "--depth", depth,
                     "--width", str(a.width), "--height", str(a.height),
                     "--strength", str(strength), "--seed", str(render_seed),
-                    "--prompt", prompt, "--negative", NEGATIVE,
+                    "--prompt", prompt, "--negative", negative,
                     "--prefix", prefix, "--wait", "300"]):
             print(f"  {tag}  RENDER FAILED"); continue
 

tools/comfy-spike/sweep_strength.py

@@ -25,6 +25,25 @@ REPO = os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__)
 COMFY = os.path.join(REPO, "tools", "comfy-spike", "comfy.py")
 VENV_PY = os.path.join(REPO, "tools", "pixelart", ".venv", "bin", "python")
 
+# The final montage needs Pillow, which only lives in the pixelart venv; the
+# renders themselves shell out to `python3 comfy.py` (stdlib only). If we were
+# launched under a Python without PIL, re-exec under the venv so one invocation
+# both renders and montages. (Without this the whole sweep runs, then dies at the
+# last step — wasting every render.)
+if __name__ == "__main__":
+    try:
+        import PIL  # noqa: F401
+    except ImportError:
+        # The venv's bin/python is a symlink back to the base interpreter, so a
+        # realpath() comparison wrongly reports "already in the venv" and skips
+        # the hop — what matters is sys.path (venv site-packages), not the binary.
+        # Guard the re-exec with an env sentinel so a still-missing PIL raises
+        # instead of looping forever.
+        if os.path.exists(VENV_PY) and not os.environ.get("_SWEEP_REEXEC"):
+            os.environ["_SWEEP_REEXEC"] = "1"
+            os.execv(VENV_PY, [VENV_PY, os.path.abspath(__file__), *sys.argv[1:]])
+        raise
+
 # Mirror bake_atlas.py's proven prompt skeleton so the sweep reflects production.
 STYLE = ("dark fantasy, ancient torchlit stone, warm orange torchlight, deep black shadows, "
          "wet stone, volumetric haze, architectural photography of an empty ruin, "