# Three Bone Chain Settings

Several FocalRig nodes use the same three-bone limb definition together with the same shared stretch and twist settings.

Nodes that use these settings:
- [Adjust Three Bone Chain](adjust-three-bone-chain.md)
- [Aim Chain](aim-chain.md) (through **Limb Adjustment**)
- [Aim Weapon](aim-weapon.md) (through **Arm Adjustment**)
- [First Person View](first-person-view.md) (through **Limb Adjustment**)

## Three Bone Chain

Use this to define the limb that should be solved.

| Property | Type | Description |
|----------|------|-------------|
| Root Bone | Rig Element Key | The root element of the chain, such as an upper arm or thigh |
| Middle Bone | Rig Element Key | The middle element of the chain, such as a forearm or calf |
| End Bone | Rig Element Key | The end element of the chain, such as a hand or foot |

## Stretch Settings

These settings control how the limb behaves when the desired effector position reaches or exceeds the chain's natural length.

| Property | Type | Description |
|----------|------|-------------|
| Allow Stretch | bool | Whether to allow stretching the limb beyond its natural length. When false, the chain stops at the soft extension limit |
| Min Bend Angle Degrees | float | The minimum bend angle between the two limb segments. This helps prevent full straightening and reduces snapping when the target passes through the extension point |
| Force Min Bend Angle | bool | If true, the limb always bends by at least **Min Bend Angle Degrees**, even when the input pose is straighter |
| Lower Segment Stretch Ratio | float | How stretch is distributed between the two segments. 0.0 = only the upper segment stretches, 1.0 = only the lower segment stretches, 0.5 = both stretch equally |

## Twist Settings

These settings twist the whole limb around the root-to-end axis so the effector rotation lines up better.

| Property | Type | Description |
|----------|------|-------------|
| Weight | float | How much of the desired twist to apply (0.0 = none, 1.0 = full) |
| Max Degrees Clockwise | float | Maximum allowed clockwise twist in degrees when looking along the limb axis |
| Max Degrees Counter Clockwise | float | Maximum allowed counter-clockwise twist in degrees when looking along the limb axis |
| Scale Twist To Clamp Limits | bool | If true, scales the twist proportionally so the limits are never reached. If false, clamps directly at the limits |