characters/skin_leg_repair.gd

@@ -1,6 +1,26 @@
 extends Object
 class_name SkinLegRepair
 
+## Keeps the HUMANOID rigid while letting the CLOTHES flow.
+##
+## That split is the whole design rule here, and it decides what every pass below
+## is allowed to touch:
+##
+##   * LIMB vertices — anything hugging a leg's own bone chain: skin, stockings,
+##     boots — are cleaned up hard. They belong to one leg, they follow it, and
+##     they hold their shape. Deforming here is a bug.
+##   * DRAPE vertices — the skirt and anything else hanging clear of both leg
+##     chains — are LEFT ALONE, so they keep swinging with the body.
+##
+## DO NOT stiffen the skirt onto the hips. It was tried (to stop it flattening at
+## a wide stride) and reverted: it makes the clothes read as a rigid shell, which
+## is worse than the flattening it fixed. Cloth is supposed to move.
+##
+## Current split, from debug/limb_deform_check.gd: the body holds 0.98 of its
+## cross-section at the knee, while the skirt is free at 0.88 — rigid limbs,
+## moving cloth.
+##
+##
 ## Stops below-the-knee geometry being dragged by BOTH legs at once.
 ##
 ## Taila's boots are skinned with weights that bleed across the centre line:
@@ -41,17 +61,7 @@ class_name SkinLegRepair
 ##      against 0.97-0.99 at the knee). Leg vertices keep at most MAX_TORSO of
 ##      hips/spine influence, and the excess goes to the leg bone that already
 ##      dominates them, so the thigh follows its own bone.
-##   4. Hang DRAPING CLOTH from the hips instead of the legs. The skirt is
+##   4. Drop any triangle still spanning the two legs below the knee. Those are
-##      weighted to both thighs so it can follow them, but at a running or
-##      jumping stride the two thighs pull it in opposite directions and it
-##      collapses flat against the body — its flared volume vanishes and the
-##      whole lower body reads as squashed from the side. Cloth that is clear of
-##      both leg bone chains keeps at most MAX_DRAPE_LEG of leg influence, and
-##      the rest goes to the hips, so the skirt holds its shape and swings as a
-##      unit. This is the "model the skirt differently from the legs" case, and
-##      it is separate from the limb work above: LIMB vertices are snapped to
-##      one leg, DRAPE vertices are taken off the legs almost entirely.
-##   5. Drop any triangle still spanning the two legs below the knee. Those are
 ##      the midline band between the ankles, which has no correct pose either
 ##      way.
 ##
@@ -63,9 +73,6 @@ const TORSO_BONE_HINTS := ["hips", "spine", "pelvis"]
 ## The most torso influence a leg vertex may keep. Some is wanted — it is what
 ## rounds the hip off — but past this the thigh stops following its own bone.
 const MAX_TORSO := 0.15
-## The most LEG influence a draping cloth vertex may keep. A little lets the
-## skirt react to the legs; more than this and a split stride tears it flat.
-const MAX_DRAPE_LEG := 0.20
 ## Ignore influences below this — they are rounding, not real weighting.
 const EPSILON := 0.005
 
@@ -139,13 +146,12 @@ static func _repair_mesh(mi: MeshInstance3D, skeleton: Skeleton3D, knee: float,
 		limb_radius: float) -> Array:
 	var side := _side_map(mi.skin, skeleton)
 	var torso_bone := _torso_map(mi.skin, skeleton)
-	var hips_slot := _hips_bind(mi.skin, skeleton)
 	var surfaces: Array = []
 	var snapped := 0
 	var removed := 0
 	for s in range(mi.mesh.get_surface_count()):
 		var arrays: Array = mi.mesh.surface_get_arrays(s)
-		var r := _repair_surface(arrays, side, torso_bone, hips_slot, knee, chain_l, chain_r, limb_radius)
+		var r := _repair_surface(arrays, side, torso_bone, knee, chain_l, chain_r, limb_radius)
 		snapped += r[0]
 		removed += r[1]
 		surfaces.append({
@@ -167,18 +173,6 @@ static func _repair_mesh(mi: MeshInstance3D, skeleton: Skeleton3D, knee: float,
 	return [snapped, removed]
 
 
-## SKIN BIND index of the hips, which is what draping cloth should hang from.
-static func _hips_bind(skin: Skin, skeleton: Skeleton3D) -> int:
-	for b in skin.get_bind_count():
-		var n := skin.get_bind_name(b)
-		if n == "":
-			var bone := skin.get_bind_bone(b)
-			n = skeleton.get_bone_name(bone) if bone >= 0 else ""
-		if n.findn("hips") != -1 or n.findn("pelvis") != -1:
-			return b
-	return -1
-
-
 ## Is each bind a torso bone? Keyed by SKIN BIND index, like _side_map.
 static func _torso_map(skin: Skin, skeleton: Skeleton3D) -> Array:
 	var out: Array = []
@@ -223,7 +217,7 @@ static func _side_map(skin: Skin, skeleton: Skeleton3D) -> PackedInt32Array:
 
 
 static func _repair_surface(arrays: Array, side: PackedInt32Array,
-		torso_bone: Array, hips_slot: int, knee: float,
+		torso_bone: Array, knee: float,
 		chain_l: PackedVector3Array, chain_r: PackedVector3Array,
 		limb_radius: float) -> Array:
 	var verts: PackedVector3Array = arrays[Mesh.ARRAY_VERTEX]
@@ -316,63 +310,7 @@ static func _repair_surface(arrays: Array, side: PackedInt32Array,
 				weights[v * per + k] /= sum
 		snapped += 1
 
-	# Step 3 — draping cloth hangs from the hips. A skirt pulled by both thighs
+	# Step 3 — drop triangles that still span the legs below the knee.
-	# at a split stride collapses flat; taking it off the legs keeps its volume.
-	if hips_slot >= 0:
-		for v in verts.size():
-			var leg_total := 0.0
-			for k in per:
-				if side[bones[v * per + k]] != 0:
-					leg_total += weights[v * per + k]
-			if leg_total <= MAX_DRAPE_LEG:
-				continue
-			# ABOVE THE KNEE ONLY. Distance from the bone chain alone is not a
-			# safe test down here: chunky footwear sits further from the ankle
-			# than the limb radius, so a boot reads as "drape" and taking its
-			# leg weight away makes it trail off the hips. A skirt hem is above
-			# the knee; boots and stockings are not.
-			if verts[v].y <= knee:
-				continue
-			# Limb vertices were already handled above; this is only for cloth
-			# that hangs clear of BOTH leg bone chains.
-			if minf(_dist_to_chain(verts[v], chain_l),
-					_dist_to_chain(verts[v], chain_r)) <= limb_radius:
-				continue
-			var k_hips := -1
-			for k in per:
-				if bones[v * per + k] == hips_slot:
-					k_hips = k
-					break
-			if k_hips < 0:
-				# No hips influence yet: take over the weakest leg slot.
-				var weakest := -1
-				var weakest_w := 2.0
-				for k in per:
-					if side[bones[v * per + k]] != 0 and weights[v * per + k] < weakest_w:
-						weakest_w = weights[v * per + k]
-						weakest = k
-				if weakest < 0:
-					continue
-				bones[v * per + weakest] = hips_slot
-				weights[v * per + weakest] = 0.0
-				k_hips = weakest
-				leg_total -= weakest_w
-				if leg_total <= MAX_DRAPE_LEG:
-					continue
-			var keep: float = MAX_DRAPE_LEG / leg_total
-			for k in per:
-				if side[bones[v * per + k]] != 0:
-					weights[v * per + k] *= keep
-			weights[v * per + k_hips] += leg_total - MAX_DRAPE_LEG
-			var total2 := 0.0
-			for k in per:
-				total2 += weights[v * per + k]
-			if total2 > 0.0:
-				for k in per:
-					weights[v * per + k] /= total2
-			snapped += 1
-
-	# Step 4 — drop triangles that still span the legs below the knee.
 	var removed := 0
 	if not idx.is_empty():
 		var keep_idx := PackedInt32Array()