Chapter 2: Drapery Families & Stress Maps

Created by Sarah Choi (prompt writer using ChatGPT)

Drapery Families (Fold Types) & Stress Maps — Costume Design Foundations

Why drapery is structure you can see

Cloth is a moving topography that reveals anatomy, pattern logic, and material in real time. Folds are not arbitrary wrinkles; they are the visible record of where the garment is tethered, where it drapes free, and where forces concentrate. For concept artists, clear drapery solves three problems at once: it sells weight and motion, it communicates fit and construction, and it gives downstream teams predictable deformation guides for simulation and rigging.

The physics you need (and no more)

Cloth behavior flows from a few variables: gravity, anchoring, stiffness vs. flexibility, surface friction, and grain direction. Gravity wants vertical pipes; anchors (seams, closures, belts, straps, pins) redirect and split folds; stiff materials create long, broad folds with sharp breaks, while soft materials generate short, dense folds with rounded transitions. Friction decides whether folds slide or stack; grain and bias control stretch and drape direction. Think like a map: anchors are mountain ridges, folds are river valleys running away from them.

Fabric parameters that drive fold language

  • Weight: heavy wool/canvas → deep, slow folds; silk/chiffon → small, frequent ripples.
  • Thickness: thick fabrics hold bevelled edges; thin fabrics show knife‑edges and transparency at peaks.
  • Stiffness: stiff → planar facets and crisp kinks; drapey → rounded arcs.
  • Surface: slick satin slides and elongates folds; brushed flannel catches and stacks.
  • Grain/Bias: along straight grain folds stack vertically; on bias they spiral and cling.

The drapery families

Although folds blend in the wild, most readable cloth falls into a few archetypes. Name them in your callouts so production and paintovers share vocabulary.

1) Pipe folds (columnar)

Long vertical cylinders formed when fabric hangs from a continuous support like a waist seam or rod. The spacing equals leftover circumference and narrows where the cloth is pinched. Use for cloaks, curtains, skirts at rest. On stiff cloth the pipes facet; on soft cloth they round.

2) Zigzag (accordion) folds

Alternating V’s caused by compression and repeated direction changes—common at elbows and knees inside bends, or at gathered cuffs. The crests point toward the compressing force. Readable even at small scales; ideal for showing hinge action.

3) Diaper (sling) folds

Suspended between two anchors (e.g., scarf caught on two points, fabric draped between belt loops). Gravity pulls a U‑shaped catenary; secondary pipes hang off the low point. Great for sashes, banners, and loose hoods.

4) Half‑lock folds

Abrupt directional change where cloth catches on an edge (belt, pocket lip, pauldron) and locks, creating a sharp kink with a short shadow wedge. Common at waistbands and sleeve hems as the fabric flips over itself.

5) Spiral (twist) folds

Torsion around a limb or body: stripes rotate, seams helical, folds wrap diagonally. Seen when a shirt is grabbed and twisted or when a skirt turns during a spin. Use to sell torque and angular momentum.

6) Drop/break folds

At hems resting on a surface (boots, seat), the fabric buckles into triangular breaks. The number and sharpness signal stiffness and length surplus. Essential for trouser hems and capes touching stairs.

7) Inert (relaxed) ripples

Small, low‑contrast ripples in areas with no active force—upper chest of a loose tee, back yoke of a shirt at rest. Keep minimal to avoid visual noise.

8) S‑curves and flares

On skirts and coats in motion, air and inertia flare panels outward creating S‑curves that echo the character’s line of action. Cuts with gores or godets exaggerate this.

Stress maps: reading where forces live

A stress map marks anchor points, force vectors, and fold flow. Draw it before detailing.

  • Anchors: closures (buttons, zips), seams (waist, yoke, armhole), straps, belts, armor edges, hand grips. Mark with dots/bars.
  • Vectors: arrows for push/pull, gravity, wind, centrifugal force.
  • Zones: compression (zigzags), tension (straightening, sheen), neutral (soft ripples). Shade lightly for clarity.

This map becomes a simulation guide and a paintover for VFX (wind/water) and animation (anticipation/follow‑through).

Tops by region: fold expectations and fit tells

Neck & collar: Stand collars create radial tension lines; soft collars roll with gentle half‑locks near the collar points. Ties and scarves produce diaper folds between knot and pins.

Shoulder & yoke: Set‑in sleeves form diagonal tension from neck to armpit under arm lift; raglans distribute into the diagonal seam lines; action pleats in yokes open into clean planar wedges.

Sleeves: Elbow flex → zigzag at inner elbow, smoothing on the outside; sleeve caps show radial pipes from the crown when arms drop; cuffs act as half‑lock edges.

Torso: Under a belt or harness, expect half‑locks at the upper and lower edges, with pipe segments trapped between. Twists create spiral folds running from hip to ribcage.

Bottoms by region: fold expectations and fit tells

Waist & rise: Tension radiates from the fly and side seams when seated; gathers at back waist release volume for bends. High back rise reduces horizontal stress lines over lumbar during reach.

Hips & seat: Sitting creates fan folds emanating from the ischial tuberosities; standing relaxes them into vertical pipes. Pocket bags imprint as soft bulges; bar‑tacks interrupt fold travel.

Thigh & knee: Knee flex yields accordion folds at the front and smooth stretch at the back; moto pants add darted panels to manage this. Cargo pockets should sit on side planes to avoid buckling in the bend.

Hem & footwear: Hem breaks stack over boots; stiff denim forms few crisp breaks; soft linen cascades many shallow ones. Treads and spur edges create local half‑locks and scuffs.

One‑pieces: routing folds across the whole

Jumpsuits and robes route force from shoulder to ankle in continuous panels; closures (diagonal chest zips, waist ties) add anchor lines that redirect flow. Drop‑seat panels create hinge zones at the glutes; articulated knees and elbows pre‑place zigzags. In gowns, train pull produces long pipe fields with periodic drop breaks where fabric kisses the floor.

Pattern logic and seam influence on drape

Seams are fences that redirect fold traffic. Princess lines absorb bust volume and reduce random chest folds; side panels with bias orientation introduce graceful diagonals; gussets at armpit/crotch change fold families from chaotic to organized by relocating stress away from primary seams. Topstitching stiffens edges, creating sharper half‑locks; facings and interfacings add hidden rigidity at collars and plackets, altering nearby fold behavior. Show these choices so modelers place topology and so sim teams set stiffness masks.

Material reads and lighting on folds

Knife edges catch thin, bright rims; rounded folds diffuse. Satin produces long specular rivers along tension; matte wool stays value‑grouped. Wet fabric collapses volume, increases clumpiness, and turns highlights into beaded tracks; dusty fabric flattens contrast and collects at ridge lines. Communicate material by how light walks across fold families, not just by texture swatches.

Motion beats and fold choreography

  • Walk: pipes in skirts swing like pendulums; trouser fronts compress at the knee with each step; jackets lag behind torso twists.
  • Run/Sprint: hems flare; back panels stretch; sleeves stream with fewer, longer folds; backpacks introduce half‑locks under straps and oscillation nodes.
  • Reach/Climb: diagonal tension from hand to opposite hip; armpit gussets open; belts bite, creating sharp kinks.
  • Turn/Spin: spiral folds dominate; pleated skirts read as radiating spokes with alternating light/dark.

Readability across cameras and LOD

At distance, render fold families, not noise: a few pipes, a clear zigzag cluster at the elbow, a flare wedge at the hem. Mid distance supports secondary folds and seam‑guided rhythms. Close‑ups earn micro‑wrinkles, seam impressions, and stitch shadows. Author a reduction plan: which fold families persist at each LOD and which collapse to painted cues.

Integration with armor, props, and hair

Armor plates create half‑locks at edges and dead zones beneath; straps yield perpendicular compression folds. Long hair over cloth dampens small folds and introduces new half‑locks where strands catch. Weapons at belts shift anchor points; scabbards pull diagonally, creating asymmetric fold fields—good for narrative.

Common failure modes and course corrections

  • Wrinkle soup: no hierarchy. → Choose a dominant family; delete noise; group values.
  • Wrong family at the joint (e.g., pipes at an elbow) → swap to zigzags and half‑locks at cuffs.
  • Directionless highlights on satin/leather → align specular with tension lines; simplify elsewhere.
  • Folds ignoring seams → reroute near seam lines and add topstitch stiffness cues.
  • Weightless hems → add break folds and scuff logic; darken underplanes.

Deliverables for production

Include: front/side/back stress maps per garment state (stand, walk, sit); fold family legend with examples; material board with stiffness/weight notes; seam influence diagram (where topstitch, interfacing, and gussets change fold behavior); and a LOD fold plan. Add a short animation beat strip showing how folds evolve across 6–8 frames of a key action.

Practice loops

  1. Over existing sketches, ink only anchors and arrows—force yourself to justify every fold.
  2. Redesign a sleeve three ways (set‑in, raglan, kimono) and compare stress maps during a reach.
  3. Take one fabric (denim vs. silk) and paint the same pose with correct family swaps, edge sharpness, and highlight behavior.
  4. Do a hem study: render five break patterns from stiff to drapey over the same boot.

Closing thought

When you name the fold family and sketch the stress map, cloth stops being guesswork and starts acting. Marry garment type, fit, and pattern logic to the right drapery families, and your costumes will move with the character instead of against them—clear in silhouette, honest in motion, and friendly to production.