Clothing

The execution model is in blender-core. The rig and weights are in blender-character-rigging, classic cloth settings in blender-simulation, and Roblox layered clothing cages in blender-export-pipelines (references/roblox.md).

One call each

scripts/garment.py -- --body Body --group Torso --name Shirt --hide-body
scripts/garment.py -- --body Body --zmin 0.45 --zmax 1.05 --name Pants --offset 0.01 --drape 40 --morphs
scripts/garment.py -- --body Body --group Torso --name Armor --offset 0.02 --thickness 0.008
scripts/garment.py -- --check Shirt --body Body          # pose the rig first: checks the current pose

How pros build game clothing

1. Shape: start from the body (extract + offset) for fitted clothes, or from flat patterns sewn by cloth sim (Marvelous Designer or Blender cloth with sewing springs) for loose ones. Simulate on the body in its rest pose (A/T).
2. Game mesh: retopo the high/sim result to clean, even quads with loops at the joints (elbows, knees, shoulders get 3 loops), then UV it. Bake folds into normal maps (blender-texture-baking) so the low mesh stays light.
3. Skin: copy weights from the body (same bones, same influences), clean them (limit 4, normalize, drop < 0.001), then blend toward smoother weights only on loose parts (skirts, coats) and add extra bones for those.
4. Hide what's covered: delete body faces under the garment (save tris, stop poke-through) or mask them per outfit. Keep one ring of skin under cuffs and collars.
5. Verify in motion: stress poses (blender-character-rigging stress_poses.py), then --check in each. Fix by easing (offset), smoothing the body there, weight tweaks, or hiding.

garment.py

• Region: --group (body vertex group, weight > 0.5) or a world --zmin/--zmax band. The faces are copied in world space and pushed out along the vertex normals by --offset (ease: 5–10 mm fitted cotton, 10–20 mm jackets, 15–30 mm armor). Then Solidify adds --thickness (2–4 mm fabric, 5–10 mm leather/armor), growing outward. UVs carry over from the body.
• Weights: Data Transfer (POLYINTERP_NEAREST, all groups by name), applied, limited to --max-influences, normalized and cleaned. The body's Armature modifier is added and parented to the rig.
• --hide-body: Hidden_<name> vertex group (the region shrunk by one ring) + an inverted Mask modifier on the body. Swappable outfits toggle masks. For export, delete those faces on a body copy instead.
• --drape N: classic cloth (cotton-ish: mass 0.15, tension 15, bending 0.5, quality 8). The top 8% is pinned, the body collides at 3 mm, it settles N frames, then the result is applied. That gives gravity folds on loose areas. Use 30–60 frames.
• --morphs: for each body shape key, a same-named garment shape key, via Surface Deform bound in the rest pose and applied as a shape key per morph. Engines drive body and garment keys together (fat/thin, muscle, breathing). Measured: a 30% body morph pokes through 346 verts. With the matching garment key, 0.
• Poke check (also run at the end of every build): casts along each body vertex normal. If the garment is hit inward before outward (or sits < 0.5 mm away), it's poke-through. Verts that hit no garment within 0.1 m aren't covered and are ignored. It reports covered_verts, poke_verts and poke_max_m, uses the evaluated pose, and respects the body masks.

Layered clothing

• Order from the skin out: underwear/base → shirt → vest → jacket → armor. Each layer offsets from the one below (run garment.py --body Shirt for a vest over the shirt) and copies weights from the body, not from the layer below.
• Interpenetration between layers in motion usually comes from mismatched weights. Copying all layers from the same body keeps them moving together.
• Roblox layered clothing needs <Name>_InnerCage + <Name>_OuterCage built from Roblox's template cages (same vert order/UVs). Other engines (UE Mutable/Unity) blend shape keys or use body-hiding masks. Same principle.

Gotchas

• shape_key_add() creates keys at value 1.0 (measured). Set .value = 0 when authoring morphs from Python.
• Surface Deform for morphs only: if left live together with an Armature modifier, the pose is applied twice. --morphs removes it after baking the keys.
• Apply the body's scale before building. Offsets and thickness are in meters.
• Cloth sims need the body's collision mesh at a modest resolution. Decimate a proxy for the collision if the body is > 50k verts.
• Run blender-asset-qa on the final garment (z-fighting with the body, floating parts, normals) and check its tris against blender-game-optimization budgets.