Chapter 2: Mobility Reads

Created by Sarah Choi (prompt writer using ChatGPT)

Mobility Reads (Gaps, Overlaps, Bellows)

Mobility is not a hidden stat; it is a visible promise your armor makes. Players and viewers infer how a character can sprint, climb, vault, kneel, and roll by reading gaps, overlaps, and bellows. This article gives character concept artists a practical, production‑ready grammar for depicting mobility across light, medium, and heavy kits—whether fantasy plate or sci‑fi shells—so designs animate correctly and remain readable at gameplay distance.

Why Mobility Language Matters

A suit that looks frozen will feel frozen, even if animation forces it to move. Clear mobility reads prevent uncanny motion, help rigging decide hinge placement and standoff, and guide texture and shader teams on what creases and what stays rigid. Design mobility first, then decorate.

The Three Signals of Movement

Gaps (intentional negative space) show where joints articulate; overlaps (shingled plates or layered textiles) show how protection remains during motion; bellows (expandable fabric/leather or mechanical concertinas) show where volume grows and collapses. A convincing kit balances all three.

Joint Atlas: Mobility by Region

Neck & Collar: Split collars with posterior lames; anterior notch for trachea. Gap reveals under‑collar knit or gambeson; overlaps protect carotids without choking. Shoulder: Floating pauldron with rear elastic bridge; deltoid crescent gap underneath; secondary bicep cop overlaps up into pauldron in abduction. Optional mini bellows panel at axilla for stealth textiles. Elbow: Tri‑lame couter shingled toward wrist; slit or keyhole for olecranon; small leather/textile gusset inside elbow acts as bellows to kill sightline to bare skin. Wrist/Hand: Flared gauntlet lip clears pisiform; glove cuff is the bellows. Keep dorsal overlap; leave palmar side soft for grip. Torso: Abdominal lames overlapping down for crunch; spine channel gap for twist; side elastics hidden by rib plates. Textile bellows at side seams for breathing. Hip/Groin: Split fauld/tasset skirts that clear thigh lift; crotch kept soft with layered textiles or concealed insert plates. Overlaps face down to shed rain. Knee: Tri‑segment poleyn with donut pad; thigh and shin plates meet under poleyn wings. Hidden textile bellows spanning popliteal fossa. Ankle: Greave flare top/bottom; small posterior gap at Achilles; gaiter or soft cuff acts as bellows for dorsiflexion.

Overlap Grammar (Shingle Logic)

Overlaps should point along motion and weather. Rule of shingle: upper overlaps lower in the direction of gravity and expected impact vectors. Document minimum overlap distances (e.g., 10–12 mm for limb lames, 20–30 mm for torso lames). Use stepped edges or fish‑scale scallops when extreme flexion is needed. Avoid back‑shingling unless a dramatic pose demands; if you must, explain with reversed threat vectors (e.g., mounted lancers or aerial descent).

Gap Discipline (Show Enough, Hide Enough)

Gaps are not holes; they are windows to a secondary layer. Always show under‑armor—knit, gambeson, spacer mesh—inside gaps to avoid the look of exposed skin where lethal. Keep gap shapes echoing the motion arc: crescents under deltoids, wedges behind knees, teardrops at elbows. Maintain standoff (10–25 mm) between plates and soft goods so shadows read and collisions don’t clip. Use witness tents—small cloth dimples between anchors—to sell tension without clutter.

Bellows: Textile, Leather, and Mechanical

Textile bellows are pleated or gusseted expansions (accordion pleats, action backs, pit zips with bellows panels). They read soft, quiet, and stealthy. Leather bellows add crease memory and audible character; they need skived edges and radius‑aware patterning to avoid cracking. Mechanical bellows (polymer concertinas, segmented flex couplers) suit sci‑fi shells; they suggest sealed systems and can carry color or hazard language. Whenever you add a bellows, define its neutral (compressed) and max (expanded) states and the crease logic; paint a wear map that darkens fold valleys and polishes crests.

Light / Medium / Heavy Mobility Profiles

Light Kits: Mobility is read through generous gaps and textile bellows; overlaps are minimal—caps at knees/elbows, slim bracers, abbreviated pauldron. Show action backs, side‑seam gussets, and hem vents. Straps are elastic‑biased; silhouette stays close to body. Medium Kits: Mobility divides evenly among the three signals. Limbs use 2–3 lames; torso has abdominal lames and side bellows; pauldron floats clearly. Gaps tighten but remain legible; add concealed knit at elbows/knees to keep coverage. Heavy Kits: Overlap becomes the hero. Multi‑lame joints everywhere; bellows move inward to textiles hidden under plates; gaps narrow to slits with clear under‑armor. Convey mass management via strong standoff, deep shadow channels, and pronounced shingle steps.

Fantasy vs Sci‑Fi Mobility Cues

Fantasy: Steel/bronze with boiled leather. Mobility reads come from hammered lames, maille in the gaps, and gambeson bellows. Edge roll, rivet cadence, and leather facings explain hinge points. Cloaks and surcoats route around plates; add slits and gussets to keep stride. Sci‑Fi: Rigid composites and thermoplastics float on webbing ladders and elastomer bridges. Mechanical bellows protect joints; insert pockets under shells provide covert soft armor. Cable runs follow strap channels; exo linkages must terminate at skeletal landmarks (pelvis, scapula plane) and show sliding collars where bones rotate.

Readability at Camera Distance

At mid‑shot, viewers should parse motion without seeing micro‑hinges. Use silhouette cut‑ins at joints, consistent chamfers on shingled edges, and shadow lanes under overlaps. Minimize surface noise on plates near joints; let the mobility language do the talking. Color‑code bellows subtly (darker, matte) to push depth reads.

Pattern & Construction for Bellows and Overlaps

  • Gussets: Diamond underarms and crotch diamonds for textiles; align grain on bias to maximize spread.
  • Action backs: Bi‑swing pleats anchored to side panels; hidden elastic bridge controls return.
  • Elbow/Knee gussets: Crescent insets of knit/spacer mesh under plate stacks; finish edges with binding to survive shear.
  • Leather concertinas: Even‑spaced folds with skived valleys; reinforce fold roots with stitch tape.
  • Mechanical concertinas: Molded TPU rings on a fabric core; integrate stop ribs to cap expansion.

Rigging & Cloth‑Sim Guidance

Declare hinge axes and overlap order on your callouts. Treat plate stacks as rigid bodies with limited‑slide constraints; set collision thickness to preserve shadow lanes. For bellows textiles, raise bend stiffness along fold roots and add plasticity to hold memory kinks. Mark no‑sim zones under rigid shells and wind‑active flags at overlap lips and cape hems. Provide neutral/expanded poses for bellows so tech art can constrain without guesswork.

Shader & Texture Notes

Mobility reads live in roughness and AO as much as albedo. Deepen AO under overlaps; brighten convex plate edges; keep bellows matte with subtle sheen on fold crests. For leather bellows, layer burnish along ribs; for mechanical bellows, add low‑frequency roughness bands and fine stress‑whitening at extreme folds. Do not over‑resolve weave/twill at gameplay distance—let highlight size and shadow depth carry the read.

Failure Modes & Maintenance

Where movement concentrates, failure begins. Textile bellows fray at fold peaks and sew lines; leather bellows craze at tight radii; mechanical bellows crack at root ribs or delaminate from fabric cores. Design service seams to replace bellows modules and indicate inspection windows in diegetic UI. Repairs: binding tape overlays on textiles, edge repaint and stitched scabs for leather, heat‑welded rings or replacement cartridges for mechanical bellows.

Packaging for Production

Deliver: 1) hinge/overlap maps with minimum overlaps by region, 2) bellows pattern diagrams (neutral vs max), 3) standoff distances and padding thickness, 4) rig notes (constraint types, slide ranges), 5) shader notes (AO/roughness guides), and 6) LOD seam maps showing how bellows collapse to simpler reads while preserving gap/overlap silhouettes.

Case Studies

Light Ranger (Fantasy): Gambeson with action‑back pleats, leather elbow/knee cops, and split tassets. Gaps show quilted underlayer; overlaps minimal; side bellows enable deep draw and climb. Readable crescent under pauldron sells abduction. Medium Trooper (Near‑Future): Composite pauldron on elastic bridge, tri‑lame elbows/knees, abdominal lames, and TPU mechanical bellows at hip flex. Gaps narrow but reveal matte knit; overlaps handle impact; bellows carry breath and stride. Heavy Breaker (Sci‑Fi): Full shell with multi‑lame joints, concealed spacer‑mesh bellows, and deep standoff shadows. Mobility reads through strong shingle steps, rigid‑to‑soft float mounts, and thin slit gaps with clear under‑armor tone.

Closing Thought

If you design where volume grows, where plates slide, and where fabric breathes—before you paint filigree—your armor will look fast when it needs speed and unyielding when it needs power. Mobility language is the difference between a costume that moves and a system that performs.