Phase 2: reskin engine — dress the nude TRELLIS bodies without fitting anything

Every anatomy body is an independent TRELLIS reconstruction: no shared topology, no vertex
correspondence, its own UV atlas. That kills garment portability — a fitted mesh can't move
between bodies. Reskin sidesteps the whole problem by repainting the atlas the body already
has, so it works on unstructured meshes and needs no rig.

Chain (/api/reskin), all local except one farm call:
  render_plates.py  -> bind-pose front/back ortho plates, EEVEE, 1024, transparent
  mflux_image_edit  -> "put <garment> from image 2 onto the person in image 1", per plate
  align_plate.py    -> re-fit the edited figure to the original bbox. The edit model redraws
                       at its own scale/offset, and the projection bake assumes the original
                       framing, so skipping this makes the body sample background.
  bake_skin.py      -> Cycles DIFFUSE projection onto the mesh's real UVs, front/back split
                       on normal.Y
Costume swapping in the browser is just a material.map change, so pre-baked outfits toggle
instantly with no re-bake; the bare map is retained so it's reversible.

Fixed a real defect in the inherited baker: planar front/back projection has no idea a head
is round, so side-facing skull polygons sampled whatever front-plate pixel sat at their x/z
and painted a ghost second face down the side of the head (clearly visible on phrtt2). Since
this tier repaints CLOTHES, the bake now keeps the body's own texture above a neck-height
cutoff (default 0.87 of body height, -1 to disable), sampling it through the mesh's real UVs.

Verified end-to-end on phrtt2 (1 mesh / 1 UVMap / 1 material / 4,364 tris — the reskin class):
farm try-on produced a convincing corduroy jacket holding the exact T-pose, and the bake put
it on the model. Known ceiling, unchanged and by design: the silhouette does not move, so this
sells tight and printed garments and reads wrong for a heavy coat.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server.py

@@ -31,6 +31,7 @@ EXTRA_BODIES = [os.path.expanduser('~/Documents/anatomy'),
 CACHE = os.path.join(ROOT, '.glbcache')
 BLENDER = os.environ.get('WG_BLENDER', '/Applications/Blender.app/Contents/MacOS/Blender')
 OPS = os.path.join(ROOT, 'blender_ops.py')
+TOOLS = os.path.join(ROOT, 'tools')       # reskin trio (NPCFACTORY) + the doll compositor (90sDJsim)
 # Creds come off disk, never off the command line. .env beside server.py (gitignored) holds the
 # CF Workers AI pair; MB_TOKEN lives in backnforth/.env — read it there rather than making every
 # launch remember `export MB_TOKEN=…` (without it the farm tiers silently die: no RMBG-2.0, no
@@ -120,9 +121,13 @@ FLAT_PROMPT = ('product photo of a single {phrase} laid flat on a plain white ba
                'slightly worn')
 
 
-def run_blender(args, jid=None):
+def run_blender(args, jid=None, script=None):
-    """One headless Blender op; stdout tail lands in the job log (when there is a job)."""
+    """One headless Blender op; stdout tail lands in the job log (when there is a job).
-    cmd = [BLENDER, '-b', '--python', OPS, '--'] + [str(a) for a in args]
+
+    script= runs a different bpy file (the reskin trio lifted from NPCFACTORY) instead of
+    blender_ops.py.
+    """
+    cmd = [BLENDER, '-b', '--python', script or OPS, '--'] + [str(a) for a in args]
     r = subprocess.run(cmd, capture_output=True, text=True, timeout=1800)
     tail = '\n'.join((r.stdout + r.stderr).strip().splitlines()[-12:])
     if jid and jid in JOBS:
@@ -318,6 +323,62 @@ class H(BaseHTTPRequestHandler):
                 json.dump(rec, f, indent=2)
             return self.j({'ok': True, 'name': name})
 
+        if u.path == '/api/reskin':               # 3D tier: paint a garment onto the body's own UVs
+            # Sidesteps the fact that every TRELLIS body is unstructured with no shared topology —
+            # instead of fitting a cloth mesh, we repaint the atlas the body already has. Needs a
+            # single-mesh / single-UV / single-material body (multi-material rigs shard the bake).
+            if not MB_TOKEN:
+                return self.j({'error': 'reskin needs the farm image-edit operator — MB_TOKEN missing'}, 400)
+            b, g = body.get('body', ''), body.get('garment', '')
+            for p in (b, g):
+                if not allowed(p) or not os.path.isfile(p):
+                    return self.j({'error': 'path outside library'}, 403)
+            desc = body.get('desc') or 'the garment in image 2'
+            jid = new_job('reskin', 'reskin ' + os.path.basename(b))
+
+            def fx(jid):
+                src = glb_of(b, jid)
+                name = slug(os.path.basename(b).rsplit('.', 1)[0]) + '--' + slug(os.path.basename(g).rsplit('.', 1)[0])
+                wd = os.path.join(DIRS['gen'], '_reskin', name)
+                os.makedirs(wd, exist_ok=True)
+                JOBS[jid]['note'] = 'rendering bind-pose plates'
+                run_blender([src, wd], jid, script=os.path.join(TOOLS, 'render_plates.py'))
+                gid = mb_upload(g)
+                outs = {}
+                for side in ('front', 'back'):
+                    plate = os.path.join(wd, f'base_{side}.png')
+                    if not os.path.exists(plate):
+                        raise RuntimeError(f'no {side} plate rendered')
+                    JOBS[jid]['note'] = f'image-edit: dressing the {side} plate'
+                    j = mb_req('/api/jobs', {
+                        'operator': 'mflux_image_edit',
+                        'asset_ids': [mb_upload(plate), gid],
+                        'params': {'prompt': f'put {desc} from image 2 onto the person in image 1. '
+                                             'Keep the exact same pose, body proportions, framing and '
+                                             'plain background. Full body visible, head to toe.'}})
+                    ji = j.get('id') or j.get('job_id')
+                    mb_wait(ji, jid, timeout=900)
+                    o = mb_outputs(ji)
+                    if not o:
+                        raise RuntimeError(f'image-edit returned nothing for the {side} plate')
+                    edited = os.path.join(wd, f'edit_{side}.png')
+                    mb_download(o[0], edited)
+                    # the edit model redraws the figure at its own scale/offset; the projection bake
+                    # assumes the original framing, so unaligned plates make the body sample background
+                    aligned = os.path.join(wd, f'aligned_{side}.png')
+                    subprocess.run(['python3', os.path.join(TOOLS, 'align_plate.py'), plate, edited, aligned],
+                                   capture_output=True, text=True, timeout=300)
+                    outs[side] = aligned if os.path.exists(aligned) else edited
+                JOBS[jid]['note'] = 'baking onto the body atlas (Cycles)'
+                tgt = os.path.join(DIRS['garments'], name + '.reskin.png')
+                run_blender([src, outs['front'], outs['back'], tgt], jid,
+                            script=os.path.join(TOOLS, 'bake_skin.py'))
+                if not os.path.exists(tgt):
+                    raise RuntimeError('bake produced no texture')
+                return tgt
+            job_thread(jid, fx)
+            return self.j({'job': jid})
+
         if u.path == '/api/doll/gen':             # 2D tier: prompt → staged paper-doll layer
             if not DOLL:
                 return self.j({'error': '2D tier unavailable — needs pillow + numpy'}, 400)

tools/bake_skin.py

@@ -51,7 +51,42 @@ mix = node('ShaderNodeMix', data_type='RGBA')
 nt.links.new(mix.inputs['Factor'], lt.outputs[0])
 nt.links.new(mix.inputs[6], texB.outputs['Color'])   # A = back
 nt.links.new(mix.inputs[7], texF.outputs['Color'])   # B = front (factor 1 when n.y<0)
-bsdf = node('ShaderNodeBsdfDiffuse'); nt.links.new(bsdf.inputs['Color'], mix.outputs[2])
+# --- keep the original head -------------------------------------------------------------
+# Front/back planar projection has no idea a head is round: side-facing skull polygons sample
+# whatever front-plate pixel sits at their x/z, which paints a second ghost face down the side
+# of the head. We're repainting CLOTHES, so above the neck we just keep the body's own texture.
+# Cutoff is a fraction of body height measured from the feet (~0.87 ≈ chin on a standing figure);
+# pass -1 to disable and bake the whole body.
+KEEP_HEAD_ABOVE = float(sys.argv[-5]) if len(sys.argv) >= 6 and sys.argv[-5].replace('.', '', 1).replace('-', '', 1).isdigit() else 0.87
+orig_tex = None
+for slot in (m.data.materials[0] if m.data.materials else None,):
+    if slot and slot.use_nodes:
+        for n in slot.node_tree.nodes:
+            if n.type == 'TEX_IMAGE' and n.image:
+                orig_tex = n.image
+                break
+
+if KEEP_HEAD_ABOVE > 0 and orig_tex is not None:
+    neck_z = mn.z + (mx.z - mn.z) * KEEP_HEAD_ABOVE
+    # original texture sampled through the mesh's REAL UVs (not the projection)
+    uvmap = node('ShaderNodeUVMap')
+    if m.data.uv_layers:
+        uvmap.uv_map = m.data.uv_layers[0].name
+    texO = node('ShaderNodeTexImage'); texO.image = orig_tex
+    nt.links.new(texO.inputs[0], uvmap.outputs[0])
+    above = node('ShaderNodeMath', operation='GREATER_THAN'); above.inputs[1].default_value = neck_z
+    nt.links.new(above.inputs[0], sep.outputs['Z'])
+    headmix = node('ShaderNodeMix', data_type='RGBA')
+    nt.links.new(headmix.inputs['Factor'], above.outputs[0])
+    nt.links.new(headmix.inputs[6], mix.outputs[2])        # below neck: the projected garment
+    nt.links.new(headmix.inputs[7], texO.outputs['Color'])  # above neck: the untouched original
+    colour_out = headmix.outputs[2]
+    print(f'keeping original head above z={neck_z:.3f} ({KEEP_HEAD_ABOVE:.2f} of height)')
+else:
+    colour_out = mix.outputs[2]
+    print('baking whole body (no head preserve)')
+
+bsdf = node('ShaderNodeBsdfDiffuse'); nt.links.new(bsdf.inputs['Color'], colour_out)
 outn = node('ShaderNodeOutputMaterial'); nt.links.new(outn.inputs['Surface'], bsdf.outputs[0])
 baketex = node('ShaderNodeTexImage'); baketex.image = tgt; nt.nodes.active = baketex
 m.data.materials.clear(); m.data.materials.append(mat)

web/index.html

@@ -149,6 +149,13 @@
     <div class="note">swatch retints the last attached item (free colourways — no re-gen).</div>
     <div class="row"><input id="fitName" placeholder="save dress-up as…"><button id="saveFitBtn" class="ghost">save</button></div>
     <div id="savedFits" class="note"></div>
+    <h2>reskin — paint it on</h2>
+    <div class="row"><button id="reskinBtn">RESKIN body + garment</button></div>
+    <div class="row"><label>costume</label><select id="costumeSel"><option value="">— bare —</option></select></div>
+    <div class="note">Bakes the garment onto the body's own UV atlas, so it works on unstructured
+      TRELLIS meshes with no fitting. Silhouette doesn't change — great for tight/printed garments,
+      wrong for a big coat. Swapping the dropdown is instant (no re-bake).</div>
+
     <h2>deforming fit (blender)</h2>
     <div class="row"><label>inflate mm</label><input id="fitInf" value="3"></div>
     <div class="row">
@@ -399,6 +406,7 @@ function renderLists() {
     else previewGarment(it);
   });
   document.querySelectorAll('.fitchip').forEach(el => el.onclick = () => loadFit(el.dataset.fit));
+  renderCostumes();
   document.querySelectorAll('[data-pick]').forEach(cb => cb.onchange = () => {
     cb.checked ? picked.add(cb.dataset.pick) : picked.delete(cb.dataset.pick);
     $('fitList').textContent = picked.size ? [...picked].map(p => p.split('/').pop()).join(' + ') : 'tick fitted items in the garments list…';
@@ -454,6 +462,34 @@ $('hangBtn').onclick = async () => {
   toast(r.note || r.error); refresh();
 };
 
+// ---------- reskin: swap the body's own texture ----------
+// The bake is the expensive part and it already happened; changing costume is just a map swap,
+// so pre-baked outfits toggle instantly. Keeps the original map so "bare" is reversible.
+const texLoader = new THREE.TextureLoader();
+$('reskinBtn').onclick = () => (BODY && GARM)
+  ? runJob('/api/reskin', { body: BODY.path, garment: GARM.path, desc: 'the ' + GARM.name.replace(/[-_]/g, ' ').replace(/\.\w+$/, '') }, 'reskin')
+  : toast('pick a body AND a garment first');
+
+function renderCostumes() {
+  const mine = (LIB.garments || []).filter(g => g.name.endsWith('.reskin.png'));
+  $('costumeSel').innerHTML = '<option value="">— bare —</option>' +
+    mine.map(g => `<option value="${g.path}">${g.name.replace('.reskin.png', '')}</option>`).join('');
+}
+$('costumeSel').onchange = e => {
+  if (!bodyRoot) return toast('load a body first');
+  const p = e.target.value;
+  bodyRoot.traverse(o => {
+    if (!o.isMesh || !o.material) return;
+    if (o.userData.bareMap === undefined) o.userData.bareMap = o.material.map || null;
+    if (!p) { o.material.map = o.userData.bareMap; o.material.needsUpdate = true; return; }
+    texLoader.load('/file?p=' + encodeURIComponent(p) + '&t=' + Date.now(), t => {
+      t.flipY = false; t.colorSpace = THREE.SRGBColorSpace;   // glTF UV convention
+      o.material.map = t; o.material.needsUpdate = true;
+    });
+  });
+  toast(p ? 'wearing ' + p.split('/').pop().replace('.reskin.png', '') : 'bare');
+};
+
 // ---------- 2D paper-doll tier ----------
 // The flat cut-outs are a first-class product, not a fallback: djsim already ships 441 of
 // them and its loader self-heals on any dropped PNG, so a layer generated here wears itself