Tattoo test bed: Quaternius v3-v6 bakes + Lena pipeline (bake, de-mirror, re-UV, viewers)

Session 2026-07-23/24 additions on top of the existing Quaternius bed:
- bake_lena.gd: 6-piece bake on QuatSkin Lena (chiefs-mark/iron-spine arms,
  voyagers/storm-bearer legs, star-eye chest, hearth-warmth back); global-axis
  wrap frame + 3cm junction blend kill the elbow split line
- demirror_lena.gd: tri-level split of mirror-shared limb UVs (arms 100%->0%,
  legs 99%->5% crotch-only residual)
- reuv_lena.gd: Quaternius-style semantic re-UV (16 islands, cylinder limbs +
  cylinder head/torso with planar caps) + texture transfer; fixes armpit/chin/
  cheek planar smears; single 4096 atlas, per-side tattoos native
- main_lena / anim_lena viewers (18 UAL clips, U light toggle) + probes + shots

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

prep.gd

@@ -0,0 +1,65 @@
+# Builds 1024² gen canvases from the per-part UV masks: the island silhouette
+# (padded bbox, aspect-true, centered) as parchment white on black. The exact
+# same transform is recomputed in composite.gd to map results back into UV space.
+# Run headless:
+#   tinqs.console.exe --headless --path tattoo-test -s res://prep.gd
+extends SceneTree
+
+const MASK_DIR := "C:/Users/CAN/tinqs-ltd/tattoo-test/masks/"
+const OUT_DIR := "C:/Users/CAN/tinqs-ltd/tattoo-test/gen-v4/"
+const PARTS := ["arm_r", "arm_l", "leg_r", "leg_l", "chest", "back"]
+const CANVAS := 1024
+const MARGIN := 48    # silhouette keeps this distance from canvas edges
+const PAD := 24       # px padding around the mask bbox in UV space
+const PARCHMENT := Color(0.97, 0.94, 0.88)
+
+func _init() -> void:
+	DirAccess.make_dir_recursive_absolute(OUT_DIR)
+	for part: String in PARTS:
+		var mask := Image.load_from_file(MASK_DIR + "mask_" + part + ".png")
+		var t := transform_for(mask)
+		var rect: Rect2i = t["rect"]
+		var s: float = t["scale"]
+		var off: Vector2 = t["offset"]
+		var canvas := Image.create(CANVAS, CANVAS, false, Image.FORMAT_RGBA8)
+		canvas.fill(Color(0, 0, 0))
+		for cy in CANVAS:
+			for cx in CANVAS:
+				var mx := int((cx - off.x) / s) + rect.position.x
+				var my := int((cy - off.y) / s) + rect.position.y
+				if mx < rect.position.x or my < rect.position.y \
+						or mx >= rect.end.x or my >= rect.end.y:
+					continue
+				if mask.get_pixel(mx, my).r > 0.5:
+					canvas.set_pixel(cx, cy, PARCHMENT)
+		var path := OUT_DIR + "canvas_" + part + ".png"
+		canvas.save_png(path)
+		print("CANVAS %s rect=%s scale=%.4f offset=%.1f,%.1f saved=%s" %
+			[part, rect, s, off.x, off.y, path])
+	quit()
+
+# shared with composite.gd — keep in sync
+static func transform_for(mask: Image) -> Dictionary:
+	var size := mask.get_width()
+	var minx := size
+	var maxx := -1
+	var miny := size
+	var maxy := -1
+	for y in size:
+		for x in size:
+			if mask.get_pixel(x, y).r > 0.5:
+				minx = mini(minx, x)
+				maxx = maxi(maxx, x)
+				miny = mini(miny, y)
+				maxy = maxi(maxy, y)
+	var rect := Rect2i(
+		maxi(minx - PAD, 0), maxi(miny - PAD, 0),
+		mini(maxx + PAD + 1, size) - maxi(minx - PAD, 0),
+		mini(maxy + PAD + 1, size) - maxi(miny - PAD, 0))
+	var s := minf(
+		float(CANVAS - 2 * MARGIN) / rect.size.x,
+		float(CANVAS - 2 * MARGIN) / rect.size.y)
+	var off := Vector2(
+		(CANVAS - rect.size.x * s) * 0.5,
+		(CANVAS - rect.size.y * s) * 0.5)
+	return {"rect": rect, "scale": s, "offset": off}