animation/characters/work/lena/14_seam_membrane.py

# Stage 14: heal the SOURCE MESH's panel-seam network. The mask viz proved the stomach/waist
# lines are the Tripo scan-panel slits (a body-wide grid), not garment edges — the paint had
# been camouflaging them. Map the raw mesh's boundary verts at 2 mm (welding moved verts ~1 mm,
# which is why a 0.5 mm map only caught a quarter of the network), grow 2, membrane across.
#   blender --background --python 14_seam_membrane.py -- <in.blend> <raw.glb> <out.blend>
import bpy, sys, time
import numpy as np
from mathutils import Vector
from mathutils.kdtree import KDTree

argv = sys.argv[sys.argv.index("--") + 1:]
BLEND, RAW, OUT = argv[0], argv[1], argv[2]
t0 = time.time()

SEAM_TOL = 0.002
Z0, Z1 = 0.28, 0.87      # whole body below the chin; face seams stay (framed by features)


def log(m):
    print(f"[seam {time.time()-t0:6.1f}s] {m}", flush=True)


bpy.ops.wm.open_mainfile(filepath=BLEND)
ob = max([o for o in bpy.data.objects if o.type == 'MESH'],
         key=lambda o: len(o.data.vertices))
me = ob.data
n_v = len(me.vertices)
co = np.empty(n_v * 3)
me.vertices.foreach_get("co", co)
co = co.reshape(-1, 3)

n_e = len(me.edges)
ev0 = np.empty(n_e * 2, dtype=np.int32)
me.edges.foreach_get("vertices", ev0)
ev0 = ev0.reshape(-1, 2)

before = set(bpy.data.objects)
bpy.ops.import_scene.gltf(filepath=RAW)
new = [o for o in bpy.data.objects if o not in before]
raw = max([o for o in new if o.type == 'MESH'], key=lambda o: len(o.data.vertices))
rme = raw.data
rn = len(rme.vertices)
rco = np.empty(rn * 3)
rme.vertices.foreach_get("co", rco)
rco = rco.reshape(-1, 3)
l_tot = np.empty(len(rme.polygons), dtype=np.int32)
rme.polygons.foreach_get("loop_total", l_tot)
l_start = np.empty(len(rme.polygons), dtype=np.int32)
rme.polygons.foreach_get("loop_start", l_start)
l_v = np.empty(len(rme.loops), dtype=np.int32)
rme.loops.foreach_get("vertex_index", l_v)
ecount = {}
for fs, ft in zip(l_start, l_tot):
    idxs = l_v[fs:fs + ft]
    for k in range(ft):
        a, b = idxs[k], idxs[(k + 1) % ft]
        kk = (a, b) if a < b else (b, a)
        ecount[kk] = ecount.get(kk, 0) + 1
rbnd = np.zeros(rn, dtype=bool)
for (a, b), c in ecount.items():
    if c == 1:
        rbnd[a] = rbnd[b] = True
for o in new:
    bpy.data.objects.remove(o, do_unlink=True)
log(f"raw boundary verts: {rbnd.sum()}")

kd = KDTree(n_v)
for i in range(n_v):
    kd.insert(Vector(co[i]), i)
kd.balance()
seam = np.zeros(n_v, dtype=bool)
for p in rco[rbnd]:
    if not (Z0 < p[2] < Z1):
        continue
    hit = kd.find(Vector(p))
    if hit[0] is not None and hit[2] < SEAM_TOL:
        seam[hit[1]] = True
log(f"seam verts mapped: {seam.sum()}")

navel = (np.abs(co[:, 0]) < 0.022) & (co[:, 2] > 0.495) & (co[:, 2] < 0.555) & (co[:, 1] < 0)


def grow_edges(mask, rings, ev):
    m = mask.copy()
    for _ in range(rings):
        hit = m[ev[:, 0]] | m[ev[:, 1]]
        m2 = m.copy()
        m2[ev[:, 0]] |= hit
        m2[ev[:, 1]] |= hit
        m = m2
    return m


free_m = grow_edges(seam, 2, ev0) & (co[:, 2] > Z0) & (co[:, 2] < Z1) & ~navel
collar = grow_edges(free_m, 2, ev0) & ~free_m
S = np.nonzero(free_m | collar)[0]
in_S = np.zeros(n_v, dtype=bool)
in_S[S] = True
glb = np.full(n_v, -1, dtype=np.int64)
glb[S] = np.arange(len(S))
se = ev0[in_S[ev0].all(axis=1)]
a_ = glb[se[:, 0]]
b_ = glb[se[:, 1]]
deg = np.zeros(len(S))
np.add.at(deg, a_, 1.0)
np.add.at(deg, b_, 1.0)
free = free_m[S]
log(f"free {free.sum()}, collar {(~free).sum()}")


def Ls(X):
    out = deg[:, None] * X
    np.add.at(out, a_, -X[b_])
    np.add.at(out, b_, -X[a_])
    return out


def A_op(U):
    X = np.zeros((len(S), 3))
    X[free] = U
    return Ls(Ls(X))[free]


Xc = np.zeros((len(S), 3))
Xc[~free] = co[S[~free]]
rhs = -Ls(Ls(Xc))[free]
U = co[S[free]].copy()
r = rhs - A_op(U)
p = r.copy()
rs = (r * r).sum()
rs0 = rs
for it in range(120000):
    Ap = A_op(p)
    al = rs / max((p * Ap).sum(), 1e-30)
    U += al * p
    r -= al * Ap
    rs2 = (r * r).sum()
    if rs2 < 1e-18 or rs2 < rs0 * 1e-14:
        break
    p = r + (rs2 / rs) * p
    rs = rs2
co_new = co.copy()
co_new[S[free]] = U
d = np.linalg.norm(co_new - co, axis=1)
log(f"membrane: {free.sum()} verts (CG {it}, rel {rs2/max(rs0,1e-30):.2e}), max move {d.max():.4f}")

me.vertices.foreach_set("co", co_new.reshape(-1))
me.update()
if me.has_custom_normals:
    vn = np.empty(n_v * 3, dtype=np.float32)
    me.vertices.foreach_get("normal", vn)
    me.normals_split_custom_set_from_vertices(vn.reshape(-1, 3))
bpy.context.preferences.filepaths.save_version = 0  # no .blend1 autosave
bpy.ops.wm.save_as_mainfile(filepath=OUT)
log(f"WROTE {OUT}")
print("SEAM_DONE")