Ep.21.1 — Thigh Inner/Outer · Double Knee

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

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

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