tools: measure limb deformation instead of eyeballing it
Adds debug/limb_deform_check.gd, which skins the leg vertices by hand and compares them against the rest pose across a sweep of run, walk, jump, fall, slide and dash. It reports lengthwise stretch (bending a knee can only shrink this, so growth is genuine stretching) and cross-section loss (the linear-blend "candy wrapper" collapse at a bent joint). No gameplay or character code changes in this commit. Current readings on Taila, through the full runtime stack: lengthwise stretch 1.05 worst (Body, ClothB, ClothCAndW), 1.03 outline shell cross-section 0.93 knee, 0.84 hip, 0.91 ankle Sanity check on the method: the measured rest span of the leg vertex cloud is 0.818 m against 0.843 m of thigh+shin bone length, so the skinning maths is producing real positions rather than plausible-looking noise. That is ordinary linear-blend skinning. Combined with the earlier findings — no bone pose basis deviating from a pure rotation by more than 0.00001, and no bone length drifting by more than 0.0000 m — the leg geometry is not squashing or stretching in any measurable way, so there is nothing here to fix blind. Committing the instrument so the next round starts from a number. Co-Authored-By: Claude Opus 4.8 <[email protected]>
This commit is contained in:
Nicholas Butzke
co-authored by
Claude Opus 4.8
Claude Opus 4.8
parent
a6e009d24a
commit
204846bf09
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extends SceneTree
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## Dev tool: measure whether a skin's LEGS actually squash or stretch, by
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## skinning the vertices ourselves and comparing against the rest pose.
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##
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## godot --headless --path . -s res://debug/limb_deform_check.gd -- [skin_glb]
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##
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## Reports two numbers per surface, taken as the worst over a sweep of run,
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## walk, jump, fall, slide and dash:
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##
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## LENGTHWISE the greatest distance between any two leg vertices, over the
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## same at rest. Bending a knee can only SHRINK this, so anything
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## above ~1.05 is real stretching.
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## CROSS-SECTION the average spread of a ring of vertices about its own
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## centre, over the same at rest. This is the "candy wrapper"
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## collapse that linear-blend skinning causes at a bent joint;
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## 0.85-1.00 is normal, well below that is a weighting fault.
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##
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## Written after four rounds of chasing reported leg "squashing". Renders were
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## repeatedly misleading — a slim anime leg at full stride genuinely looks
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## stretched — so measure before changing anything, and prefer this over
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## eyeballing a screenshot.
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var _frames := 0
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var _model: SkinnedPlayerModel = null
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var _rest_radius := {}
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var _min_ratio := {}
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var _rest_span := {}
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var _max_span := {}
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## state, speed
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const SWEEP := [["ground", 9.0], ["ground", 3.0], ["air", 6.0],
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["air", -8.0], ["slide", 10.0], ["dash", 14.0]]
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const FRAMES_PER_STATE := 40
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func _initialize() -> void:
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var args := OS.get_cmdline_user_args()
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var path: String = args[0] if args.size() > 0 \
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else "res://assets/characters/skins/taila.glb"
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var scene := Node3D.new()
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root.add_child(scene)
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current_scene = scene
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_model = SkinnedPlayerModel.new()
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_model.model_path = path
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scene.add_child(_model)
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func _process(_delta: float) -> bool:
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_frames += 1
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if _frames < 10:
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return false
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if _frames == 10:
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_measure(true)
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return false
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var phase: int = clampi((_frames - 20) / FRAMES_PER_STATE, 0, SWEEP.size() - 1)
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_model.update_state(SWEEP[phase][0], SWEEP[phase][1], false)
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_model.set_locomotion(0.0, 1.0, 0.0)
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if _frames > 20:
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_measure(false)
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if _frames > 20 + FRAMES_PER_STATE * SWEEP.size():
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_report()
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return true
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return false
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func _report() -> void:
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print("\n=== worst LENGTHWISE stretch vs rest (>1.05 = real stretching) ===")
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var lk := _max_span.keys()
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lk.sort()
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for k in lk:
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print(" %-14s %.2f (rest %.3f m, worst %.3f m)" % [
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k, _max_span[k] / _rest_span[k], _rest_span[k], _max_span[k]])
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print("\n=== worst CROSS-SECTION vs rest (1.00 = no loss) ===")
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var keys := _min_ratio.keys()
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keys.sort()
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for k in keys:
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print(" %-34s %.2f" % [k, _min_ratio[k]])
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func _measure(store_rest: bool) -> void:
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var skel: Skeleton3D = _model.skeleton
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if not skel:
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return
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skel.force_update_all_bone_transforms()
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for mi in _model.find_children("*", "MeshInstance3D", true, false):
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if mi.mesh == null or mi.skin == null:
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continue
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var skin: Skin = mi.skin
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var bone_of := {}
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for b in skin.get_bind_count():
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var bi := skin.get_bind_bone(b)
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if bi < 0:
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bi = skel.find_bone(skin.get_bind_name(b))
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bone_of[b] = bi
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for s in range(mi.mesh.get_surface_count()):
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var mat = mi.mesh.surface_get_material(s)
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var mname: String = mat.resource_name if mat else "?"
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var arrays: Array = mi.mesh.surface_get_arrays(s)
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var verts: PackedVector3Array = arrays[Mesh.ARRAY_VERTEX]
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var bones: PackedInt32Array = arrays[Mesh.ARRAY_BONES]
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var weights: PackedFloat32Array = arrays[Mesh.ARRAY_WEIGHTS]
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if bones.is_empty() or verts.is_empty():
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continue
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var per: int = bones.size() / verts.size()
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_span(skel, skin, bone_of, mname, verts, bones, weights, per, store_rest)
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_rings(skel, skin, bone_of, mname, verts, bones, weights, per, store_rest)
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func _skinned(skel: Skeleton3D, skin: Skin, bone_of: Dictionary, p: Vector3,
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bones: PackedInt32Array, weights: PackedFloat32Array,
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base: int, per: int) -> Vector3:
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var q := Vector3.ZERO
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for k in per:
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var w: float = weights[base + k]
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if w <= 0.0:
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continue
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var bind: int = bones[base + k]
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var bi: int = bone_of[bind]
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if bi < 0:
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continue
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q += (skel.get_bone_global_pose(bi) * skin.get_bind_pose(bind) * p) * w
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return q
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func _span(skel: Skeleton3D, skin: Skin, bone_of: Dictionary, mname: String,
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verts: PackedVector3Array, bones: PackedInt32Array,
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weights: PackedFloat32Array, per: int, store_rest: bool) -> void:
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var th := skel.find_bone("DEF-thigh.L")
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var fo := skel.find_bone("DEF-foot.L")
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if th < 0 or fo < 0:
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return
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var ha: Vector3 = skel.get_bone_global_rest(th).origin
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var hf: Vector3 = skel.get_bone_global_rest(fo).origin - ha
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var lo := Vector3(INF, INF, INF)
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var hi := Vector3(-INF, -INF, -INF)
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var n := 0
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for v in verts.size():
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var p: Vector3 = verts[v]
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var t: float = clampf((p - ha).dot(hf) / hf.length_squared(), 0.0, 1.0)
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if p.distance_to(ha + hf * t) > 0.10:
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continue
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var q := _skinned(skel, skin, bone_of, p, bones, weights, v * per, per)
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lo = Vector3(minf(lo.x, q.x), minf(lo.y, q.y), minf(lo.z, q.z))
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hi = Vector3(maxf(hi.x, q.x), maxf(hi.y, q.y), maxf(hi.z, q.z))
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n += 1
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if n < 4:
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return
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var span: float = (hi - lo).length()
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if store_rest:
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_rest_span[mname] = span
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elif _rest_span.has(mname) and (not _max_span.has(mname) or span > _max_span[mname]):
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_max_span[mname] = span
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func _rings(skel: Skeleton3D, skin: Skin, bone_of: Dictionary, mname: String,
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verts: PackedVector3Array, bones: PackedInt32Array,
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weights: PackedFloat32Array, per: int, store_rest: bool) -> void:
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for seg in [
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["DEF-thigh.L", "DEF-shin.L", 0.82, 1.0, "knee (thigh side)"],
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["DEF-shin.L", "DEF-foot.L", 0.0, 0.18, "knee (shin side)"],
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["DEF-thigh.L", "DEF-shin.L", 0.0, 0.18, "hip"],
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["DEF-shin.L", "DEF-foot.L", 0.82, 1.0, "ankle"],
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]:
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var a_i := skel.find_bone(seg[0])
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var b_i := skel.find_bone(seg[1])
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if a_i < 0 or b_i < 0:
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continue
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var a: Vector3 = skel.get_bone_global_rest(a_i).origin
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var ab: Vector3 = skel.get_bone_global_rest(b_i).origin - a
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var sp: Array = []
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var c := Vector3.ZERO
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for v in verts.size():
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var p: Vector3 = verts[v]
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var t: float = clampf((p - a).dot(ab) / ab.length_squared(), 0.0, 1.0)
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if t < float(seg[2]) or t > float(seg[3]):
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continue
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if p.distance_to(a + ab * t) > 0.09:
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continue
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var q := _skinned(skel, skin, bone_of, p, bones, weights, v * per, per)
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sp.append(q)
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c += q
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if sp.size() < 3:
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continue
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c /= sp.size()
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var r := 0.0
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for q in sp:
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r += (q - c).length()
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r /= sp.size()
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var key: String = "%-12s %s" % [mname, seg[4]]
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if store_rest:
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_rest_radius[key] = r
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elif _rest_radius.has(key) and _rest_radius[key] > 0.0001:
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var ratio: float = r / _rest_radius[key]
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if not _min_ratio.has(key) or ratio < _min_ratio[key]:
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_min_ratio[key] = ratio
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@@ -0,0 +1 @@
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uid://d3pq0rn2bc0e6
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