# Ep.22.1 — Upper Arm Shoulder Module

https://youtu.be/i7gTfVvmDOs
https://youtu.be/nhH-hxcj3Yk

## Overview

A short update: **Skirt** left **Hip Extra** on the Build tab, and **Upper Arm** took that slot. It corrects the shoulder when the arm folds and unfolds, and it does not affect Twist.

## What's covered

| Section | Content |
|---------|---------|
| Where | Hip Extra: Hip, Upper Arm, Calf, Forearm. Skirt slot → Upper Arm |
| Role | Shoulder corrective on fold and unfold. Twist stays put |
| Amount | A-Pose is 0°. About 45° down gives Weight 1. Everyday Z is 1–2, closer to 1 |
| Direction | Skirt, ponytail, tail, and hair stay customization. Focus is the base skeleton and correctives |

## Related

- **Ep.22** — Elbow · Hip Corrective
- **Ep.21** — Double Knee
- **Ep.21.1** — Thigh inner/outer
- **Ep.16–18** — Customizing (hierarchy · layers · naming)

## Steps

1. **Hip Extra** on the **Build** tab lists Hip, Upper Arm, Calf, and Forearm. Skirt left this slot and Upper Arm replaced it.
2. Match **Default**, then **Build**. Check the module in the **Picker**.
3. Turn off **Figure Mode**. The module corrects the silhouette as the shoulder folds and unfolds. Twist must not move, so this module does not drive it. The module sits at front/back, side, and mid points.
4. There was a request for Push when the shoulder drops. On the gear **Start**, A-Pose Current Angle is **0**. Lowering reaches about **45°**, and Weight from 0° to 45° becomes **1**.
5. **Unlock** and set position **Z**. The video uses Z **10** only to show the difference. The upper angle stays. Only the lower part pushes.
6. Do not use it that strong day to day. **1 or 2** is enough, and about **1** is only a small thickness correction. That is the added shoulder bone.

## Product direction

- Skirt, ponytail, tail, and hair differ by studio. There was also a request that Spring Magic did not work on a skirt. Those parts stay **customization**, with a guide so teams handle them in-house, rather than as default modules.
- The focus is a stable, higher-quality humanoid **base skeleton**, then widening the service from that skeleton.
- Customizing is covered in other videos. Do not stop at the provided template. After you understand the structure, bone names and layer names may change for a production.
- More attention goes to **correctives** such as the shoulder bone. **Double Knee** is also a base-skeleton module for a more realistic thigh. What is needed now is not more attached parts, but modules that make the base skeleton solid.
- This shoulder is a base module. A more advanced shoulder-muscle rig is a later direction.

## Related

- **Ep.22** — Elbow · Hip Corrective
- **Ep.21 / Ep.21.1** — Double Knee · thigh inner/outer
- **Ep.16–18** — Customizing

Contact: `contact@otakusolutions.com`  
Product: [BipedPlus](https://otakusolutions.com/ko/biped-plus)