Your first armature prompt
Ask the agent to "add bones" and it drops a tidy chain floating beside the model, or buried at the world origin, with every bone roll arbitrary — a skeleton that looks like a rig and deforms like a disaster the moment you move it.
Choose your track
Read this module through your lens
A skeleton is only as good as its placement
Rigging adds an armature — a hierarchy of bones — so the model can be posed and animated. The agent can create a bone chain instantly, and it will look like a rig: a clean line of bones with a sensible hierarchy. But a rig is judged entirely by where the bones sit, and placement is exactly what the agent gets wrong.
Bones must live inside the model’s real joints — the elbow bone at the elbow, the knee bone at the knee. The agent, working from text, has no reliable sense of where those joints are in your specific mesh, so it tends to drop the chain beside the model, or center it at the world origin, detached entirely. Worse, each bone has a “roll” (its rotation around its own length) that the agent sets arbitrarily, which scrambles how poses behave later.
The dangerous part: a misplaced rig looks fine in rest pose. It only reveals itself when you move it — and by then it is wired into everything.
The case study: rigging a desk lamp
”Add bones to this articulated desk lamp so it can be posed.”
A three-bone chain appears — but it is standing vertically beside the lamp, not along its arm. The hinge bones do not sit at the lamp’s actual hinges, so bending bone 2 would fold the shade, not the joint. Bone rolls are random, so the shade would twist when posed. In rest pose, though, it all looks plausible.
”Place bone_base head at the lamp foot, tail at the lower hinge. bone_lower head at the lower hinge, tail at the upper hinge. bone_head head at the upper hinge, tail at the shade mount. Roll each bone so its Y points along the arm segment. Parent the mesh. Report each bone’s head/tail.”
Bones now sit on the actual hinges. The reported positions match the lamp’s joints; one roll is off by 90 degrees — a single fix — and the lamp poses at its real pivots.
Anchor bones to landmarks, then check by moving
The fix is the same shape as everything in this course: the agent cannot see your mesh, so you convert what you see into explicit instructions. For rigging that means naming the landmark for each bone’s head and tail — “head at the foot, tail at the lower hinge” — rather than asking for “a rig.” Coordinates derived from real joints beat any generic skeleton.
Then inspect in two stages. First, view the bones inside the mesh from at least two angles in rest pose, confirming each sits in its joint rather than floating nearby. Second — and this is the rigging-specific habit — actually rotate a bone a little. Rest pose hides every placement and roll error; a single test rotation reveals whether the joint folds where the real hinge is, or somewhere absurd.
A product model you can judge standing still. A rig you can only judge in motion.
Hands-on exercise
Take an articulated object (the lamp, or a model with obvious joints). Prompt “add bones so it can be posed” and record where the agent puts them — likely beside or through the mesh. Then list each bone’s head and tail by mesh landmark, prompt again with those and a roll instruction, and view the result from two angles. Finally, rotate one bone a few degrees and note whether it folds at the real joint. Capture the rest pose and the test rotation.
Second case · a swing-arm monitor mount
The same lesson, a different object
Add bones to this monitor arm so it can be posed.
A three-bone chain lands beside the arm, not on its pivots. Bone rolls are random. In rest pose it looks like a rig — but a single test rotation folds the wrong segment, not the actual hinge.
bone1 head at the base pivot, tail at the elbow; bone2 elbow to wrist; bone3 wrist to the mount. Roll each bone so Y runs along its segment. Parent the mesh and report head/tail positions.
Bones now sit on the real pivots; a test rotation folds at the hinge. Same rule as the lamp: anchor to landmarks, then judge by moving, never by rest pose.
Common failures · spot them fast
The failure gallery
Bones float beside / behind the mesh, not inside the joints
Whole armature at world origin, detached from the model
Arbitrary bone roll (axes point random directions)
Wrong hierarchy (parenting order scrambled)
Agent reports rig added with no positions given
Each of these is caught by a quality gate — keep the cheatsheet open while you work.
Worked example
Watch the journey
The pattern
Cheatsheet
Cheatsheet
Prompt skeleton
Add an armature to [model]. Place bones at these landmarks:
[bone: head at <landmark>, tail at <landmark>], ...
Orient each bone's roll so [axis] points [direction].
Parent the mesh to the armature. Report each bone's head/tail position and roll.
Failure modes
- Bones float beside / behind the mesh, not inside the joints
- Whole armature at world origin, detached from the model
- Arbitrary bone roll (axes point random directions)
- Wrong hierarchy (parenting order scrambled)
- Agent reports rig added with no positions given
Key operations
- Place bone head/tail at mesh joint landmarks
- Set bone roll / orientation deliberately
- Build the parent hierarchy (spine -> limbs)
- Parent mesh to armature (with the chosen method)
- Read back bone positions vs. the mesh
Quality gates
- Does each bone sit inside its real joint?
- Is the hierarchy correct (parents before children)?
- Are bone rolls consistent / intentional?
- Did the agent report head/tail positions?
Workflow steps
- List the joints and their mesh landmarks
- Prompt with explicit head/tail + roll
- View bones in-mesh from two angles
- Fix the misplaced bone, re-check
- Log the bone position table
Next module
- rig_weights_and_skinning — where auto-weights betray you.
Reflection
Reflection card
Active retrieval — answer from memory before re-reading. Saved to this browser.
You've completed this module when…
- An armature whose bones sit at the model's real joints, shown from two angles.
- A bone position table reported by the agent and checked against the mesh.
- One misplaced bone caught and repositioned.
Next: rig_weights_and_skinning — where auto-weights betray you.
Finish — back to Rigging & Animation →