Rigging: skeletons & skinning Project 2 launch

Mon 2:00 · Brief Bones, hierarchy, and skin

Rigging is building the puppet. Get the skeleton and the skinning right and animation is a joy; get them wrong and every pose fights you. This is the least glamorous week and the one that saves you the most pain later.

Joints and hierarchies

A rig is a tree of bones (Blender calls them bones; Maya calls them joints — same idea). Each bone is the child of another, so rotating the shoulder carries the elbow, wrist, and fingers with it. That parent-child hierarchy is the whole trick: you pose a few high-level controls and the chain follows. Build the hierarchy wrong — a bone parented to the skip-a-generation ancestor — and limbs detach in ways that are maddening to debug.

The humanoid skeleton

Humanoid rigs share a standard skeleton: a spine chain, a head, two arm chains (shoulder, upper arm, forearm, hand), two leg chains (thigh, shin, foot, toe). This standardization is what lets you retarget animation from one humanoid to another later — in Unreal, the IK Retargeter maps one humanoid Skeleton onto another. The bones sit at the anatomical joints — the elbow bone pivot goes exactly where your elbow bends, not an inch off, or the deformation lies.

Rigify, and Maya as the alternative

Blender's Rigify add-on generates a full, production-grade control rig from a metarig — a simplified skeleton you position to match your character. It gives you IK/FK limbs, foot rolls, and clean controls without hand-building hundreds of constraints. Maya's HumanIK and rigging tools do the equivalent job; we teach Rigify because it's free and in our default DCC, but the concepts port directly. Either way, you'll export the deform skeleton — the bones that actually skin the mesh — for Unreal.

Skinning and weight painting

Binding the mesh assigns each vertex a set of weights — how much each nearby bone influences it. Automatic weights gives a fast, usually-decent guess based on proximity. But automatic weights always struggle at high-deformation zones: shoulders, elbows, hips. Weight painting is you correcting that guess by hand — literally painting influence onto vertices — until the mesh creases and stretches like flesh over bone instead of shrink-wrap.

Mon 2:45 · Guided lab Rig a humanoid, fix the joints

Metarig to control rig to clean deformation to an Unreal Skeletal Mesh — the full first pass on your character.

1. First, five minutes for next week: install Claude Code and Codex

   The agent lab starts Week 09, and its first minutes should go to directing the agent, not installing it. Install both CLIs now — they are small — and sign in once from your project directory. Install only: no agents touch this week’s work.

   Exact steps

   1. Install Claude Code: follow code.claude.com/docs — one install command for your OS — then cd into your project root, run claude, and sign in.
   2. Install the Codex CLI from github.com/openai/codex, then run codex from the project root and sign in.
   3. Always launch an agent from inside the project folder — that is how it sees your files.

   Done when both claude and codex start from your project root without errors.

2. Add the metarig

   With your mesh in a T/A-pose, Add → Armature → Human (Meta-Rig) from Rigify. If your character isn't humanoid, block a simple joint chain by hand instead and follow the same skinning steps.

3. Position the metarig

   In edit mode, move each metarig bone to sit exactly at your character's joints — shoulders, elbows, wrists, hips, knees, ankles. Use front and side views. This alignment is the single biggest determinant of deformation quality.

4. Generate the control rig

   In the Rigify panel, click Generate Rig. This builds the full control rig with IK/FK switches and posing widgets from your metarig. The metarig is now just the blueprint; you animate the generated rig.

5. Parent with automatic weights

   Select the mesh, shift-select the rig, and Ctrl+P → With Automatic Weights. Blender binds every vertex to nearby bones. Grab a control and pose an arm — it moves, imperfectly. That's expected.

6. Enter weight paint mode

   Select the mesh, switch to Weight Paint mode, and pick a bone to inspect its influence. Red is full influence, blue is none. Now you can see exactly where the automatic guess went wrong.

7. Fix shoulders and hips

   Pose the arm up and the leg out, then paint weights until the shoulder and hip crease instead of collapsing or spiking. Smooth harsh transitions with the Blur brush. These are the two zones that make or break a humanoid.

8. Test-pose the whole rig

   Run the character through extreme poses — arms overhead, deep crouch, head turned. Watch for pinching, volume loss, and candy-wrapper twists at the forearm and shin. Fix each as you find it.

9. Export and import as a Skeletal Mesh

   Export the mesh with its deform skeleton to FBX (apply transforms, +Z up / -Y forward for Unreal), then import into Unreal with Skeletal Mesh checked. Unreal creates a Skeletal Mesh, a Skeleton asset, and a Physics Asset. Because this is humanoid, note the plan: keep the bone set clean so you can retarget onto it later via the IK Retargeter — you'll wire that up when animation clips arrive.

Wed 2:00 · Workbench Practice, unhurried

No new material. You work on your own file while I circulate — this is the hour where the technique from the guided lab stops being something you watched and becomes something you can do.

1. Finish the lab on your own work

   The guided lab was built on the class example. Now do it on the piece you are actually submitting. That second pass is where it sticks.

2. If you fell behind, catch up here

   This is what the hour is for. Say so and I will come to you — do not spend it quietly stuck.

3. If you are ahead, go deeper

   Take the optional extensions from the lab, or push the piece further than the brief asks. Nothing graded depends on them.

4. Ask Gary, the AI TA, anything

   The tutor on the course site is open all term for questions about how and why. It explains; you build. No agents in the work until Week 9.

Wed 3:10 · Crit / share Project 2 launch & rig share

Project 2 — the Rigged & Animated Character — launches today; read the full brief on the course hub. Bring your rig to the front and pose it live through two extremes while the room watches the shoulders and hips. We're not judging animation yet — only whether the puppet is trustworthy enough to animate. A rig that deforms cleanly through crit is a rig you'll thank yourself for in three weeks.

Homework — due before Week 09

Resources

• Claude Code docs — install and sign-in, for the Week 09 agent lab.
• Codex CLI — install and sign-in, for the Week 09 agent lab.
• Blender Rigify docs — generating and customizing the humanoid control rig.
• Blender weight paint docs — brushes, normalization, and fixing influence.
• Mixamo — auto-rigging reference and a source of test animation to retarget onto your UE skeleton.
• Unreal Skeletal Mesh assets — importing a rigged character and how the Skeleton asset drives retargeting.