Arche Extensions

A Blender add-on for Human Generator characters — bind garment weights properly, manage clothing, and repair what a Rigify conversion breaks.

Not affiliated with Human Generator or Auto-Rig Pro. Contains no code from either and requires no modification to them.

Button	What it does
Bind Weights	Skins a garment to the character (body weights for hugging garments, else Auto-Rig Pro voxel bind, else Blender bone heat), cleans up, hides the skin under the cloth, copies the body's corrective shape keys, and verifies every frame.
Mask Skin Under Garment	Just the skin mask, on a garment whose weights you already like. Removes a shrinkwrap guard if one is there.
Add to Character Clothing	Tags a mesh placed on the character as HumGen clothing and binds it. Optional HumGen fitting for garments built on the default body.
Add to Clothing Asset Library	Saves one garment to your library, not the whole outfit.
Remove Clothing	Deletes garments and the body masks they added, so no holes are left behind.
Re-bind Clothing to Rigify	Fixes clothing that stopped following the rig after a Rigify conversion.

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Why Bind Weights exists

HumGen's own weighting runs a single data_transfer with vert_mapping="NEAREST" and no cleanup at all. Measured on a 29,736-vertex shirt against HG_Body:

• 72.9% of vertices had weights that did not sum to 1 — 2,676 of them under 0.5, so they followed the armature at less than half strength
• a median of 5 bone influences per vertex, against the body's 2
• 58 vertex groups holding no weight whatsoever

Clipping vertices counted across 7 poses:

	7 poses	at rest
HumGen data_transfer NEAREST + cleanup	10,539	1,482
Auto-Rig Pro pseudo-voxel bind	3,611	321

Auto-Rig Pro's bind_to_rig() with the PSEUDO_VOXELS engine works on a Rigify rig, not just ARP rigs, binds in ~16 s, and assigns the twist bones (DEF-upper_arm.L.001) that surface transfer never touches.

What the bind does

1. Engine ladder — when the garment hugs the skin (median rest distance under 1.5 cm) the body's own weights are copied first: identical deformation, nothing to disagree. Otherwise Auto-Rig Pro pseudo-voxel bind (resolution slider, clamped 3–8, default 7) → Blender bone-heat automatic weights → surface transfer. The first engine that leaves under 10 % of vertices unweighted wins. ARP and HumGen are both optional.
2. Clean up — cap influences at 4, drop dead and non-deform groups, fill any unweighted vertex, normalise every vertex to exactly 1.0.
3. Drop far-away bones by proximity, never by name — a bone stays only if the skin it drives on the body lies near the garment. A bone the body has no group for (HumGen has no DEF-jaw) goes. The old name blacklist stripped DEF-toe off shoes and, matching ear, DEF-forearm off every sleeve.
4. Remove arm bleed from the chest — otherwise the chest sloshes when an arm moves.
5. Soften the seam with a per-group smooth.
6. Hide the skin under the cloth (default) — a MASK modifier on the body over the skin the garment covers. Coverage is found by ray casts from each skin vertex: cloth up to 4 cm in front of it, or a panel buried up to 8 cm inside the body (a shirt sat 6.3 cm deep — a nearest-point test never reaches that). Hits within 1 cm of the garment's open edges don't count, so the cut line always sits under the cloth. The garment mesh is never touched. This is what HumGen's own library garments do. Alternative: a Shrinkwrap guard (outside surface, 4 mm, last in the stack) — fine on loose garments, visibly deforms a dense body-hugging one.
7. Copy the body's corrective shape keys — HumGen's skin bulges at elbows and shoulders through pose-driven keys (cor_ElbowBend_Lt…). Every driven body key becomes a garment key (nearest-vertex delta) with the same driver on the rig. Without them identical weights still let 150–250 vertices of skin through a sleeve on an elbow bend.
8. Verify every frame — garment vertices inside visible skin counted on each frame of the scene range and reported in the status bar. Sampled checks have passed animations that were broken in between.

A Corrective Smooth modifier on the garment with factor > 0.5 is reported as a warning: at factor 1.0 × 20 iterations it pulled sleeves 3 cm off the skin on every arm raise (256 vertices through the cloth; 10 with it off).

Install

1. Download the latest arche_extensions-*.zip from Releases.
2. Edit ▸ Preferences ▸ Add-ons ▸ Install from Disk…, pick the zip, enable Arche Extensions.

Blender 4.0+. Auto-Rig Pro is optional but strongly recommended — without it the binder falls back to surface transfer.

Upgrading from v1.x? Remove the old single-file Arche FX - HumGen Tools add-on first. Both register the same operators and will collide.

Use

Press N in the 3D view. The buttons appear as an Arche Extensions panel in two places, so they are wherever you happen to be working:

• inside the HumGen tab
• in its own Arche FX tab

Everything is also in the F3 search menu.

Adding a garment: place it on the character with the rig at rest pose (the shape gets corrected to the A-pose, so a posed rig bakes in the wrong shape), select it, then Add to Character Clothing. Add clothing before converting to Rigify where you can.

Notes for anyone forking this

Test against use_deform bones, not all bones. Rigify carries plain-named control bones (foot.L, f_index.01.L, eyeball.L) that collide with HumGen's un-prefixed group names. On a garment that genuinely did not deform, 37 groups still matched a bone name. Only use_deform bones move mesh.

Rigify limbs default to IK (IK_FK = 0.0). Verify a fix by rotating an FK control and nothing moves — a perfectly working rig looks broken. Pose through foot_ik.L / hand_ik.R.

Never raise ARP's voxel resolution to 12. On a 30k-vert closed-solid garment it ran 221 minutes and reached 20.5 GB before it had to be killed. ARP's own tooltip: "Low values may sometimes work better than high values." The slider here is capped at 8. Diagnose a stuck bind by memory growth, not CPU — rising RAM with low CPU is runaway allocation that will never finish.

Do not try to append() into another add-on's panel. bpy.types.HG_PT_CLOTHING is the very class you get by importing it, yet its _draw_funcs stays empty after append(), so the buttons never render and nothing reports an error. Register your own panel with bl_category set to their tab name instead. And do not create the second panel as a subclass of the first - registering it lets Blender clobber the base class's bl_category, silently moving the original tab.

Smooth one vertex group at a time (group_select_mode='ACTIVE'). Smoothing with 'ALL' collapsed influences to a median of 1 bone per vertex.

outfit.add_obj's docstring says "top", but the corrective shape key JSON keys it as "torso" — passing "top" raises KeyError.

arp_pseudo_voxels_type='2' binds faster (8.6 s vs 16 s) but produced no usable weights on a real garment, so it is not exposed.

What it deliberately does not do

Touch your body masks. The binder only changes weights. Mask painting is yours.

It also cannot fix a garment whose topology fails. A closed-solid scanned garment with no armhole seam still stretches ~9.6× at the armpit under a high arm raise even with correct weights — that needs mesh work, not rigging. (A garment merely modelled inside the skin is handled by the collision guard.)

Refit your mesh. Human Generator's own add_obj assumes a garment built on the default HumGen body and reshapes it onto the character — on a shirt already fitted to the character it moved the mesh 14 cm up and 30 cm forward. Add to Character Clothing therefore defaults to Tag only; pick HumGen fitting only for default-body garments.

Verified

Against a real character, Blender 4.5.11:

• Guards — pose, body masks and weights all restored after a deliberate exception
• Shirt, 3,281 verts — ARP 16 s, 11 groups (jaw and thighs dropped by proximity), 0 unweighted, influences med 2 / max 5; inside the body over 123 frames: mean 3, max 21, worst 0.4 cm (before: ~950 per frame, 5 cm)
• Shoe, 183 verts — DEF-foot.L + DEF-toe.L, guard after Subsurf: mean 0, max 5, worst 0.4 cm (guard placed before Subsurf: 164)
• Without ARP — bone-heat path binds the same shirt in 0.4 s with equivalent results
• Dense shirt, 31,284 verts, on a HumGen male (v2.3, mask instead of guard) — vertices through visible skin over seven test poses: rest 3,326 → 10, arms side 5,549 → 10, arms up 6,616 → 10, arms front 7,004 → 11, torso twist 3,489 → 14. The two poses that keep a residual are self-intersecting (forearm pressed 100° into the chest; a 45° bow folding the hips under the trousers).
• Preservation — body masks, shape keys, drivers, cloth tag, mask_0 and the user's pose unchanged after a bind; the guard is the only modifier added

Licence

GPL-3.0-or-later. See LICENSE.