Rigging

Rigging

Functional rigs supporting intended motion. Clean deformation. Engine-compatible bone hierarchies.

When to Use

• Character/creature deformation rigs
• Mechanical constraint rigs
• Facial expression rigs
• Prop rigs (doors, vehicles, weapons)
• Before any animation work

Workflow

Skeleton Design → Bone Placement → Hierarchy → Constraints/IK
    → Weight Painting → Deformation Test → Export Prep

Armature Naming

Prefix: ARM_[AssetName] Bones: [side]_[region]_[name] — e.g., L_arm_upper, spine_01, jaw

Bone Hierarchy

ARM_Character
├── root
├── spine_01 → spine_02 → spine_03
│   ├── L_clavicle → L_arm_upper → L_arm_lower → L_hand
│   └── R_clavicle → R_arm_upper → R_arm_lower → R_hand
├── L_leg_upper → L_leg_lower → L_foot → L_toe
└── R_leg_upper → R_leg_lower → R_foot → R_toe

IK vs FK

Use IK	Use FK
Legs (ground contact)	Spine (flexible arc)
Arms (hand placement)	Shoulder overlap
Feet planting	Finger detail
Mechanical reach	Whip/tail motion

Standard: IK legs, FK spine; switchable arms for game characters.

Constraints

Constraint	Use
IK	Limb positioning
Copy Rotation	Mechanical sync
Limit Rotation	Joint ranges
Stretch To	Tentacles, pistons
Child Of	Weapon attach/detach
Shrinkwrap	Ground contact (use carefully)

Weight Painting

1. Automatic weights as starting point only
2. Clean weights: normalize per vertex (max 4 influences)
3. Smooth problematic areas (shoulders, hips)
4. Test extreme poses: T-pose, arms up, crouch, jaw open
5. Gradient weights at joints — no hard 1.0/0.0 at bend center

Mechanical Rigs

• Empty objects as control handles
• Constraints instead of weight painting
• Hinge limits match real joint ranges
• Parent hierarchy mirrors mechanical assembly

Facial Rigs

Approach	Use Case
Bone-based	Game characters
Shape keys	Cinematics, dialog
Hybrid	Hero game characters

Minimum game facial: jaw open, blink L/R, brow up/down.

Drivers

• Gear rotation sync
• Auto eyelid blink
• Weapon reload mechanism
• Procedural antenna/wire motion

MCP Integration

1. Create armature via MCP
2. Parent mesh with automatic weights via MCP
3. Query bone count and hierarchy
4. Validate weight groups via MCP if supported
5. Export armature with mesh via export-pipeline

Deformation Test Poses

• T-pose / A-pose (bind pose)
• Arms fully raised
• Deep crouch
• Neck rotation extremes
• Jaw wide open (characters)

Constraints

MUST DO

• Rig after retopology complete
• Name bones consistently
• Limit bone influences to 4 per vertex (game engines)
• Test deformation at extremes before animation
• Document control scheme for animators

MUST NOT DO

• Auto weights without cleanup (hero assets)
• Scale bones in bind pose
• Rig before topology validated
• Skip IK pole targets on limbs
• Mix multiple root bones without documentation

Reference Guide

Topic	Reference	Load When
Humanoid rig	references/humanoid-rig.md	Characters
Mechanical rig	references/mechanical-rig.md	Props, vehicles