A rig that survives the trip 60 min

Brief · 15 min What a rig actually is

A rig is two things that people usually conflate: a skeleton, which is a hierarchy of bones, and a binding, which is the answer to the question "when this bone moves, which vertices come with it, and how much?"

The second part is where all the difficulty lives. Every vertex in your mesh carries a set of weights — one number per nearby bone, between 0 and 1, and they sum to 1 across all the bones influencing that vertex. A vertex with weight 1.0 on the upper arm follows the upper arm exactly. A vertex on the shoulder seam might sit at 0.5 upper arm and 0.5 chest, so it moves halfway between them and the surface bends smoothly.

When a shoulder crumples into an ugly pinch as you raise the arm, the geometry is not broken and the bones are not wrong. The weights in that region are simply distributed badly — too abrupt a handoff from one bone to the next. Knowing that is what turns weight painting from guesswork into a fix.

Build · 45 min Metarig to bound mesh

1. Turn Rigify on

   Edit → Preferences → Add-ons, search Rigify, tick it. It ships with Blender but is off by default, which means it does not appear in any menu until you enable it — a genuinely confusing five minutes if nobody tells you.

   

2. Add the metarig and fit it to your mesh

   Add → Armature → Human (Meta-Rig), then enter Edit mode (Tab — Day 0’s key, and it works on armatures too) and move each bone so it sits where that bone would sit inside the body. Elbows at the elbow, knees at the knee, the spine actually inside the torso.

   Can’t find it? It is not lost — look in the Outliner: metarig is listed there. In the viewport it is hiding inside your mesh: with the metarig selected, open the green Armature Data tab and under Viewport Display tick In Front — the bones now draw through the body, and stay visible while you fit them. It also appears at the 3D cursor, at human height — so if your model is far away, much bigger, or much smaller, move and scale the metarig in Object mode to match, then Ctrl+A → All Transforms, Day 1’s habit, before you fit a single bone.

   This step is the job. It is unglamorous and it takes most of your time, and a badly fitted metarig cannot be rescued afterwards — you will spend an hour weight painting around a problem that was five minutes of bone placement. Work from the front and side views, and check the joints from both.

   

   

3. Generate the rig

   With the metarig selected, go to the Armature Data tab (the green stick figure) and in the Rigify panel hit Generate Rig. Rigify builds a full control rig from your metarig: IK/FK switching, control shapes, the works. Keep the metarig — if you need to change proportions later, you fix the metarig and regenerate.

   The panel also shows a note — This metarig uses the old face rig — with an Upgrade Face Rig button stacked above Generate Rig. Ignore both. They concern facial animation, which this course never touches, and Generate Rig works as-is. Generation takes a few seconds — Blender has not frozen.

   

   

4. Bind the mesh

   Select the mesh, shift-select the generated rig, then Ctrl+P → With Automatic Weights. Blender makes a reasonable first guess based on proximity. It is a first guess, not an answer.

   

5. Weight paint the joints that fail

   Getting in: this step alternates between two modes, both on the mode dropdown you used for Sculpt mode on Day 2. Select the rig and switch to Pose Mode — the bones become control shapes you can click, and the same G and R from Day 0 now move and rotate them. Pose the arm up, the leg forward, the spine twisted, and look for pinching.

   Then, to paint: click the rig, Shift-click the mesh, and switch to Weight Paint mode — that order matters. Enter it from the mesh alone and the bones are not selectable; enter it rig-first and you can Ctrl-click any bone to see that bone’s weights painted across the surface, with the pose held so the pinch stays visible while you fix it. Smooth the transitions where the surface collapses. Shoulders and hips are where this always goes wrong, because they have the largest range of motion and the most bones competing for the same vertices.

   Also hunt for stray influences — a single vertex somewhere in the mesh accidentally weighted to a distant bone, producing one spike that shoots across the model when that bone moves. They are easy to fix and maddening to find later.

   

Check · the four rules What Unreal requires

A rig can be flawless in Blender and still import as a mess. These four are the reasons, and every one of them is checkable in under a minute before you export.

1. A root bone, named root, at the origin

   Top of the hierarchy, sitting at 0,0,0, and separate from the pelvis — not the pelvis renamed. This bone is what root motion drives. Without it, a character that should stride forward will instead run in place while the collision capsule slides off without them.

2. Deform bones only

   Rigify generates control bones (the shapes you grab) as well as DEF- bones (the ones that actually move geometry). Unreal wants the second kind. Export everything and you get a skeleton stuffed with dozens of junk bones, which makes retargeting miserable and animation blueprints hard to read.

   

3. Applied transforms on the armature

   Day 1, again, and this is where it matters most. Unapplied scale on an armature produces animation that is correct in Blender and wrong in Unreal, with no visible cause. If you check one thing before exporting a character, check this.

4. .L and .R suffixes, intact

   Blender's mirroring and pose-flipping work entirely by bone name. Rename upper_arm.L to something tidier and mirroring stops working — silently, with no error, which is how you lose twenty minutes wondering why paste-flipped is doing nothing.