Chapter 2: Rig Notes

Created by Sarah Choi (prompt writer using ChatGPT)

Rig Notes for Mecha: Joint Ranges, Cable Slack, Deform Risks

Rig notes are the bridge between how a mech looks and how it moves in the actual game. In a mecha pipeline, you can have a gorgeous design that collapses the moment it animates: shoulder plates collide, elbows expose empty cavities, cables stretch like rubber, and “cool” silhouettes become impossible to pose. Rig notes prevent that. They turn your concept art into a readable set of motion rules that design, animation, rigging, physics, AI, VFX, and audio can all build from.

This article is written equally for concept artists on the concepting side and on the production side. If you are concepting-side, rig notes help you protect the fantasy early by making motion plausible without slowing ideation. If you are production-side, rig notes help you stabilize the asset across iterations and reduce the interpretive burden on downstream teams.

What rig notes are (and what they are not)

Rig notes are not a full rig spec and they are not a list of software settings. They are design intent for motion. They describe joint ranges, the type of motion (hinge, slide, twist), clearance assumptions, cable and hose behavior, and known risk areas where deformation or collision is likely.

In other words, rig notes say: “This is how the mech should behave so it stays believable and stays on-model.” That is valuable to everyone. Designers use it to balance moves and set hit volumes. Animators use it to choose posing and timing. Riggers use it to build constraints and solve deformation. Physics uses it to determine what can collide or simulate. AI uses it to select attacks and navigation behaviors. VFX and audio use it to place events and feedback at the right moments.

Why mecha needs rig notes more than people expect

Mecha sits between character animation and vehicle mechanics. A human character can rely on natural deformation rules. A vehicle can rely on rigid transforms. Mecha often needs both: rigid armor shells plus controlled flex zones, sliding layers, telescoping pistons, and cable bundles that behave believably.

Without rig notes, teams default to convenience. Armor that should slide will just clip. Cables that should slacken will stretch. Retractable fins will be ignored. The mech will still ship, but its motion will contradict its design language, and players will feel that contradiction.

Rig notes are how you preserve the “mechanical truth” that makes mecha satisfying.

The core categories of rig notes

A useful rig note set usually covers three major categories.

First, joint ranges: how far a joint can rotate, which axes matter, and which movements are limited by armor, pistons, or hard stops.

Second, cable slack and flexible elements: where hoses, wires, or belts live; how much slack they have; where they anchor; and whether they should compress, coil, or slide.

Third, deform risks and collision risks: the areas likely to break the illusion, such as armpits, hip shells, knee plates, and backpack intersections.

Everything else is optional. If you cover these three categories well, you will remove a large percentage of downstream ambiguity.

Joint ranges: designing motion as part of silhouette

Joint range notes begin with a simple question: what is the mech’s functional posture? A brawler needs deep crouch and torso twist for wind-ups. A sniper needs stable shoulder articulation to aim without wobble. A flyer needs wide hip and shoulder ranges to stabilize in air. A heavy tank mech may have reduced range but compensate with larger foot clearance and bracing behaviors.

For concepting-side artists, you don’t need degrees; you need “bounds.” For example: “Elbow bends to a right angle; beyond that, forearm armor hits bicep shell.” “Shoulder raises overhead only if the shoulder plate slides back.” “Hip twist is limited; torso swivel provides aim.” These are readable constraints that keep animation honest.

For production-side artists, degrees can be helpful if your team uses consistent ranges. You can express them as approximate: “knee 0–110°,” “ankle ±25° pitch, ±15° roll,” “torso yaw ±45°.” The goal is not precision; it is alignment.

Motion types: hinge, slide, twist, telescoping, and “float”

Mecha joints are rarely pure hinges. Many require compound motion. A shoulder might rotate and slide to clear armor. A knee might hinge while a piston telescopes. A wrist might twist inside a cuff with a sliding collar.

A simple vocabulary makes this easy to communicate. If you label a zone as hinge-only, rigging will prioritize rotation. If you label it as hinge + slide, rigging will know to add driven translations or corrective shapes. If you label it as telescoping, the model may need internal geometry to avoid exposure.

A “float zone” is also worth naming. This is a controlled gap that exists so the mech can move without showing impossible intersections. Float zones are often covered by seals, bellows, or overlapping plates. If you do not name them, the gap might be eliminated in modeling, and then motion becomes impossible.

Cable slack: the difference between “rubber wires” and believable machinery

Cables and hoses are where many mechs look fake in motion. If they stretch like elastic, the mech feels like a toy. Slack behavior is what makes them feel engineered.

A cable slack note identifies three things: anchor points, slack reservoir, and travel path. Anchor points are where the cable begins and ends (for example, “upper arm rear → forearm underside”). Slack reservoir is where extra length lives (for example, “coiled loop behind elbow” or “accordion sleeve inside bicep shell”). Travel path is how the cable moves through bends (for example, “slides along guide rings,” “tucks into channel,” or “floats with limited swing”).

For concepting-side artists, you can show this with a simple draw-over: two anchor dots, one loop indicating slack, and a short note like “loop tightens on extension.” For production-side artists, you can add warnings: “Do not allow visible stretching; prefer spline IK with length preservation and loop compression.”

Cable management as design: guides, clamps, and safety logic

Cables are not just decoration. In real machines, cables are routed and protected. In a mech, the same logic helps readability and rigging.

When you include guide rings, clamps, brackets, and protective sleeves, you are giving rigging and physics places to constrain behavior. You are also giving VFX and audio opportunities: sparks from a damaged clamp, rattling from a loose bracket, electrical arcing from a severed line.

If the mech has a “serviceable” look, add quick-release couplers and labeled harness bundles. If it’s a high-end prototype, use hidden channels and clean gaskets. Both can be riggable; the difference is the visual story.

Deform risks: where mechs break when they animate

Even though mecha is mostly rigid, deform risks still exist. They happen in places where rigid parts need to appear continuous, or where multiple layers must slide without exposing emptiness.

Common risk zones include shoulder armpits, hip sockets, knee backs, elbow cavities, neck bases, and backpack-to-torso junctions. These are zones where motion reveals interior structure. If that interior is not designed, the rig will expose a void.

A deform risk note can be as simple as: “Deep shoulder raise exposes inner frame—needs internal detail or shadow cover.” Or: “Knee back must not collapse; include bellows or inner plate.” These notes allow modeling to build the necessary inner layer and allow rigging to plan corrective solutions.

Clearance and collision notes: what is allowed to intersect

Not all intersections are equal. Some are acceptable if they are hidden or if the parts are cosmetic. Some are unacceptable because they break the fantasy.

A good rig note clarifies collision expectations. For example: “Antenna arrays are cosmetic and can ghost slightly.” “Shoulder armor must never clip the head silhouette.” “Back cannons retract during sprint; do not collide with door frames.”

These notes partner directly with design and physics. If a part is allowed to ghost, gameplay collision can ignore it. If a part must not clip, the rig may need constraints and the animation set may need adjusted poses. If a part retracts, VFX and audio need cues.

Metrics, motion, behavior: rig notes as gameplay support

Rig notes should connect to the mech’s behavior. If the design promises a long-reach melee, note where the shoulder and torso need to extend and how the weapon arcs. If the mech has a stomp AOE, note foot contact behavior and how the ankle compresses. If the mech has a recoil-heavy cannon, note bracing: heel anchors, hip locking, torso compression, stabilizer deployment.

This is where partnering with design is strongest. Designers can tune hit boxes and timing more confidently when the rig supports the intended motion. Animators can sell weight and power when the rig has the right limits and assists.

AI also benefits. If the mech cannot twist hips far, AI can favor torso-aim behaviors. If a weapon requires bracing time, AI can telegraph and commit.

Physics notes: what should simulate and what should be driven

Mecha can include physics-simulated elements: hanging cables, antenna sway, cloth banners, loose armor flaps. But simulation is not always desirable. It can create visual noise or break silhouette clarity.

Rig notes can specify which elements are “driven” (animated intentionally) versus “simulated” (secondary motion). For example: “Cable bundle has subtle sway only; no wild whipping.” “Antenna sway is minimal; keep sensors readable.” “Loose skirt armor is stiff; small jiggle only.”

These notes help physics and animation align with gameplay readability. They also help audio: simulated parts may rattle, driven parts may have hydraulic cues.

VFX and audio hooks: making rig moments readable

Every rig behavior can be reinforced with VFX and audio. Sliding armor can have a soft metallic scrape and a brief dust puff. Telescoping pistons can have hydraulic hiss. Cable tension can have a subtle creak. A joint hard stop can have a sharp clack and a micro spark.

Rig notes can call out where these hooks belong. “Elbow hard stop at full extension—add clack.” “Backpack retract triggers servo whine.” “Knee compression on landing—add dust and bass thump.” These cues help players feel the mech’s metrics through feedback.

The format: how to write rig notes without turning into a tech manual

Rig notes work best when they are attached to images. A short sheet with callouts is more usable than a long document. A good structure is: one “range of motion” page, one “cable and flexible elements” page, and one “risk zones and clearance” page.

For concepting-side artists, keep the notes light and visual. Use arrows, simple diagrams, and plain language. For production-side artists, add consistency: approximate ranges, named pivots, and a small legend for motion types (hinge, slide, twist, telescoping).

The goal is readability. Anyone should be able to look at the sheet and understand how the mech moves.

What production-side teams should request from concept

If you are on the production side, a small set of requests can dramatically improve rig outcomes. Ask for one extreme pose set (deep crouch, overhead reach, full twist). Ask for a cable routing diagram with anchor points and slack zones. Ask for a list of “must not clip” silhouettes. Ask for any retractable behaviors to be explicitly described.

Also ask for priorities. If the schedule is tight, it matters whether the mech’s “perfect motion” is essential to its fantasy or whether some clipping is acceptable. Rig notes can include this: “Priority 1: silhouette stays clean in combat camera. Priority 2: elbow cables behave. Priority 3: micro antenna sway.”

A mindset that keeps everyone aligned

Rig notes are not about restricting creativity. They are about making your mech’s motion believable and consistent with its design promise. When you write rig notes, you are partnering with design, animation, rigging, physics, AI, VFX, and audio by giving them the rules of the body.

If you remember one principle, make it this: motion is part of the design. A mech that cannot move the way it looks like it should is a broken character. Rig notes are how you protect the character.

When rig notes are done well, concepting-side artists iterate with confidence, production-side artists hand off with clarity, and downstream teams build faster with fewer surprises. The mech feels powerful not just because it looks powerful, but because it behaves powerfully in the hands of the player.