# Ep.21.1 — Thigh Inner/Outer · Double Knee

https://youtu.be/flejVek4Lcs
https://youtu.be/rLg6RbG_DFs

## Overview

Follow-up to **Ep.21 Double Knee**. Calf thickness was fine, but the thigh-squash Controller still moved the whole thigh. This episode splits that motion into **inner** and **outer**.

The inner and outer areas have to split along the center line. The three thigh parts are divided inner/outer so fold and jiggle can separate.

## What's covered

| Section | Content |
|---------|---------|
| Problem | One squash Controller driving the whole thigh |
| Build | Double Knee Seg was 3 only; now **2 / 3 / 5** |
| Controller | One becomes two. Attribute channels move to the gear Controller |
| Push | After Unlock, vertical Scale **0.7**, side Scale **1.2** |
| Weight | Split front/back (inner/outer) Weight in SkinLayer Studio |
| Apply | In 3ds Max, squash the inner/back side and let it spread sideways |

## Related

- **Ep.21** — Advanced Rigging Module · Double Knee
- **Ep.6** — Problems with Max skinning · SkinLayer Studio

## Build · Controller

1. On the **Build** tab, turn on **Double Knee**. Seg used to be **3** only. It is now **2 / 3 / 5**. Run **Build**.
2. Check the **Picker**. Base use matches the previous rig module. Attribute channels that were on the main Control now sit on the **gear Controller**. Tuning them is the same as Ep.21.
3. Right-click a **Layer** to select only that node, then **Isolate** it.
4. The change that matters: one Controller is now **two**. When the thigh bends, the outer side is bone and moves less. **Push Weight** drives the inner side.
5. **Unlock**, then set vertical Scale to **0.7** and side Scale to **1.2** so only the contacting back flesh pushes.

## Weight in SkinLayer Studio

Stock 3ds Max Skin makes this front/back split hard. Layers are **Thigh**, **Mask**, and **Calf**. Inner thigh-bone weights run as 1, 2, and 3. The lower layer is **Calf Out** (outer) and the upper layer is **Calf In** (inner). Here In/Out means thigh inner/outer Weight.

1. Calf In and Calf Out share the same Weight and, together, move like one bone. Moving both shows a clean arc.
2. Copy the Weight onto the upper layer. **Influence Change** keeps the Weight and only swaps the assigned bone from Out to In.
3. After the bones are assigned, paint **Mask** on the back only. Stem Weight stays the same. Only the front and back regions split.

## Apply in 3ds Max

- After the front/back split, a bent thigh squashes **only the back/inner side**.
- The earlier Double Knee scaled the whole thigh down and nudged the bone up. That is closer to a cheat than anatomy. Flat subculture materials hide it. Realistic materials may show it.
- Squash only the inner side with vertical Scale **0.7**, and add side Scale so flesh spreads. The video shows a mid-thigh pass and a side scale around **1.5**.
- Prefer **Scale** over position. Position changes per character. A scale of 1.5 becomes 1.5× width when the thigh folds, and stays less awkward across proportions. With front and back split, games can push the squash harder. Subculture legs need a slightly strong squash to read as alive.

## Notes

- Extra leg bones placed per character are treated here as **one-off hardcoding**. This module is **general**: move the joint point and the thigh module follows. Moving the joint can break skin data. The rig system itself is described as unaffected.
- Bone hierarchy and scale handling are already prepared for the engine.
- Finer Weight cleanup is left for a later pass. Button names that are not in the video are not added here.

## Related

- **Ep.21** — Double Knee main episode
- **Ep.6** — Why use SkinLayer Studio

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