Bones & regions

The two canonical reference tables every modeller and item author needs: the 20-bone EF biped (the only skeleton meshes skin to) and the body regions (the values you put in an item’s regions array). Both are verified against the mod’s code.

The 20-bone EF biped

The skeleton is the official Epic Fight biped — exactly 20 joints, case-sensitive names. The renderer builds this skeleton in Java (TiedUpArmatures.buildBiped) and matches your GLB’s bones to it by name. A mistyped joint name is silently ignored — the mesh deforms wrong, with no error in the log.

Naming rules

• Underscore _ separator, never a dot. Hand_R, never Hand.R.
• First letter of each word uppercase. Thigh_R, never thigh_R or THIGH_R.
• Right/left suffix is _R / _L only. No .R, no Left/Right words.
• Start from the official rig (EpicFight_Animation_Rig_OFFICIAL.blend). Don’t rebuild the skeleton by hand — subtle rest-transform differences cause skinning artifacts at runtime.

Exact joint names

Root,
Thigh_R, Leg_R, Knee_R,
Thigh_L, Leg_L, Knee_L,
Torso, Chest, Head,
Shoulder_R, Arm_R, Elbow_R, Hand_R, Tool_R,
Shoulder_L, Arm_L, Elbow_L, Hand_L, Tool_L

Hierarchy

Root
├── Thigh_R
│   ├── Leg_R
│   └── Knee_R
├── Thigh_L
│   ├── Leg_L
│   └── Knee_L
└── Torso
    └── Chest
        ├── Head
        ├── Shoulder_R
        │   └── Arm_R
        │       ├── Elbow_R
        │       └── Hand_R
        │           └── Tool_R
        └── Shoulder_L
            └── Arm_L
                ├── Elbow_L
                └── Hand_L
                    └── Tool_L

EF's unusual parenting (verified against the code)

The arm and leg chains are not a straight Arm → Elbow → Hand line. In the actual armature (TiedUpArmatures.buildBiped):

• Elbow and Hand are both children of Arm (siblings). Elbow is the auxiliary “middle joint” used for arm bending; the forearm (Hand) hangs directly off Arm. Tool is the only child of Hand.
• Leg and Knee are both children of Thigh (siblings), for the same reason.

This matches Epic Fight’s biped.json. It only matters if you parent custom bones or read the raw hierarchy; for ordinary weight-painting you just skin to the joint by name.

Per-joint reference

Joint	Role
Root	Global root — do not keyframe it for a worn-item animation
Thigh_R / Thigh_L	Hip
Leg_R / Leg_L	Upper leg
Knee_R / Knee_L	Lower leg / foot (the “foot” is the same joint as Knee in EF)
Torso	Lower spine
Chest	Upper spine / ribcage
Head	Head (vanilla head tracking applies unless an animation overrides it)
Shoulder_R / Shoulder_L	Clavicle / shoulder pivot
Arm_R / Arm_L	Upper arm — in EF naming, “Arm” already means upper arm
Elbow_R / Elbow_L	Forearm — in EF naming, the forearm is called “Elbow”
Hand_R / Hand_L	Hand
Tool_R / Tool_L	Tool attachment point (usually left at identity)

Naming differences vs other conventions

Coming from a generic Blender rig, Mixamo, or another mod? Translate your names:

Common Blender / external name	TiedUp EF name	Note
root	Root	Uppercase
Spine / Spine1	Torso	No number
Spine2 / Chest	Chest
Shoulder.R / Clavicle.R	Shoulder_R	Dot → underscore
Upper_Arm.R / UpperArm.R	Arm_R	”Arm” already means upper arm
Forearm.R / LowerArm.R	Elbow_R	Forearm is called Elbow in EF
Hand.R	Hand_R	Dot → underscore
Thigh.R	Thigh_R
Leg.R (upper)	Leg_R
Foot.R / Knee.R	Knee_R	Foot is the same joint as Knee_R in EF
—	Tool_R / Tool_L	No common equivalent

Weight limits

Hard limit: 3 bones per vertex (EF-JSON / mesh limit)

At most 3 bones per vertex. The 4th-strongest weight is silently dropped at load (SingleGroupVertexBuilder); the symptom is visible distortion at joints when the pose leaves rest. In Blender: Object Data Properties → Vertex Groups → Weights → Limit Total = 3, then Normalize All.

You don’t need to skin to every joint. The GLB exporter only writes bones that actually have skinned vertices, and the renderer matches by name against the full biped — so a blindfold GLB listing only Head is perfectly fine. Partial bone lists are optimal, not a limitation.

Body regions

Every item declares one or more body regions in its regions array. The 14 values below are the complete, exact set the parser accepts (matched against BodyRegion, case-insensitive — the parser uppercases your input). An unknown region name is dropped with a WARN (often a “did you mean…?” suggestion); if every region is invalid, the whole item is skipped.

Region table

Region	Global?	Typical items	Joints it tends to skin to
HEAD	global	Hood, helmet, head harness	Head
EYES	sub of HEAD	Blindfold	Head
EARS	sub of HEAD	Earplugs	Head
MOUTH	sub of HEAD	Gag, muzzle	Head
NECK	—	Collar, choker	(cosmetic — Chest or Head)
TORSO	—	Straitjacket, harness	Torso, Chest
WAIST	—	Belt, chastity belt	Torso, Chest
ARMS	global	Handcuffs, armbinder	Shoulder_R/L, Arm_R/L, Elbow_R/L, Hand_R/L, Tool_R/L
HANDS	sub of ARMS	Mittens, fist mitts	Hand_R/L (+ arm chain as needed)
FINGERS	sub of ARMS	Finger cuffs	(cosmetic — Hand_R/L)
LEGS	global	Ankle cuffs, leg binder	Thigh_R/L, Leg_R/L, Knee_R/L
FEET	sub of LEGS	Forced shoes, foot cuffs	Knee_R/L
TAIL	—	Tail plug (pet play)	(cosmetic — adjacent joint)
WINGS	—	Decorative wings	(cosmetic — Chest)

The 'joints' column is authoring guidance, not a rule the code enforces

A BodyRegion carries no joint list in code — it is only a gameplay slot. The region you pick does not restrict or auto-select which joints your mesh skins to, and it does not decide which joints an animation may pose. Skinning is governed by your vertex groups; animation coverage is governed by the joints array in an OVERLAY binding (see Animations). The right-hand column above is the conventional skinning for each region, not an automatic mapping.

Global vs sub-regions

Three regions are global (isGlobal() == true on the enum) — they conceptually encompass sub-regions:

Global	Sub-regions
HEAD	EYES, EARS, MOUTH
ARMS	HANDS, FINGERS
LEGS	FEET

Blocking is NOT automatic

A hood occupying HEAD does not automatically block EYES, EARS, or MOUTH. The global flag is metadata only — it carries no auto-block behaviour. If you want an item to block its sub-regions, declare them explicitly in blocked_regions. (Conversely, a tiara on HEAD can leave EYES free for a separate blindfold.) See Item JSON for blocked_regions.

Cosmetic-only regions

NECK, FINGERS, TAIL, and WINGS have no biped joint of their own. Items in these regions render by skinning to whichever adjacent joint makes sense (e.g. a collar skinned to Chest, a choker to Head), but they do not change the player’s pose. They behave like any other region for slot occupancy and blocked_regions.

How the two tables connect

1. Pick the region(s) for your item from the 14 above and put them in regions. This drives slot occupancy, escape difficulty, and (if you declare it) blocking.
2. Skin your mesh to the relevant joint names from the biped — the names, not the region, determine deformation.
3. (optional) If the item forces a pose, list the same joint names in an OVERLAY binding’s joints array so the animation drives only those joints.

For the full item schema see Item JSON; for the build-it-once tour see Your First Item.