Bone Chain Setup

This guide explains how to set up bone chains in KawaiiPhysics.

Selecting Root Bone

Root Bone specifies the parent bone of the bone chain to apply physics to.

warning

Physics is not applied to the Root Bone itself. Physics is applied to its child bones and below.

Auto-detection

KawaiiPhysics automatically detects child bones from the Root Bone and constructs the chain.

spine_03 (Root Bone - no physics)
├── hair_front_01  ← Physics applied
│   └── hair_front_02  ← Physics applied
└── hair_back_01   ← Physics applied
    └── hair_back_02   ← Physics applied

Exclude Bones

You can exclude specific bones from physics calculation.

UPROPERTY()
TArray<FBoneReference> ExcludeBones;

Use Cases

• Parts you don't want to move, like ribbon knots
• Bones you want to control with a different KawaiiPhysics node

Multiple Bone Chains

You can use multiple KawaiiPhysics nodes for one character.

AnimGraph
├── KawaiiPhysics (for hair)
├── KawaiiPhysics (for tail)
└── KawaiiPhysics (for clothing)

tip

Parts with different parameters are easier to adjust when managed with separate nodes.

Additional Root Bones

Version Info

Added in v1.17.0

You can set multiple RootBones in a single KawaiiPhysics node. Useful when you want to control multiple bone chains with the same parameters.

Setup

1. Select KawaiiPhysics node
2. Add elements to Additional Root Bones array
3. Set additional RootBone for each element

FKawaiiPhysicsRootBoneSetting

Property	Type	Description
RootBone	FBoneReference	Additional control root bone
OverrideExcludeBones	TArray<FBoneReference>	Exclude bones list specific to this root bone
bUseOverrideExcludeBones	bool	Enable exclude bones override

Usage Example

// Control front and back hair with one node
RootBone: hair_front_root
AdditionalRootBones:
  - RootBone: hair_back_root
  - RootBone: hair_side_l_root
  - RootBone: hair_side_r_root

Benefits

• Reduced Node Count: Combine into one node if parameters are the same
• Performance: Slightly more efficient than multiple nodes
• Easier Management: Parameter changes apply to all at once

Comparison with Traditional Method

Method	Benefits	Drawbacks
Multiple Nodes	Different parameters for each part	More nodes
Additional Root Bones	Manage all with same parameters	Difficult to fine-tune per part

tip

Recommended to use Additional Root Bones for parts you want to animate with the same parameters like hair, and use separate nodes for parts that need different parameters like skirt and tail.

Bone Length and Radius

Each bone's length is automatically calculated. Radius can be set manually or controlled with curves.

For more details, see Curve Editor.