Chapter 4: Scaling / Grade Logic for NPC Pools & Customization

Created by Sarah Choi (prompt writer using ChatGPT)

Scaling & Grade Logic for NPC Pools & Customization

Why grading strategy matters for NPCs

NPC pools live at the intersection of believability, variety, and budget. A robust grading strategy lets you multiply a few base designs across body types, heights, and identities without breaking silhouette consistency or production feasibility. For concept artists, grading foresight shapes seam placement, motif carriers, and ease allocation. For production, it defines pattern families, rig compatibility, and texture reuse. When slopers, ease, darts, and grading work as a system, your world reads diverse and engineered—not random.

Slopers first: archetype families, not one body

Begin by defining sloper families—near‑body, minimal‑ease patterns—across your NPC archetypes (e.g., slim, average, robust; petite, regular, tall; chest/hip proportion variants; mobility‑assist bodies). Each sloper records lengths (CB/CF, waist‑to‑hip, armhole depth), girths (chest/bust, waist, hip, biceps, thigh), and slopes (shoulder, side seam). From these, derive block variants (shirt, jacket, pants, skirt) with baseline wearing ease, then layer design ease per role (laborer vs. clerk vs. guard).

Concept rule: Don’t sketch to one idealized mannequin. Cycle through slopers when ideating. If a design fails on a second archetype, fix it in the block, not with decorative patching.

Grade ranges and increments: the NPC size grid

Establish a grid that covers typical gameplay silhouettes at the intended camera distance—often 5–9 sizes across 2–3 height bands. Choose increments that reflect realistic apparel grading (e.g., 2–4 cm chest/hip increments, 1–2 cm at waist, controlled changes in lengths). Avoid uniform scaling; distribute changes where anatomy demands them (armhole depth increases slower than chest; crotch length increases differently front vs back).

Production note: Document a size map linking each grade to rig blendshapes or body sliders. Keep knee, elbow, and crotch heights aligned to skeleton joints to preserve animation fidelity.

Grading methods: proportional vs. controlled

  • Proportional (percentage) grading preserves relative shapes but can drift critical landmarks; good for stylized worlds at mid‑distance.
  • Controlled (rule‑based) grading sets fixed deltas at specific points (e.g., +0.3 cm cap height per size, +0.8 cm chest width per size) with constraint anchors (armhole depth, crotch length, dart apex). Use controlled grading for garments intersecting with animation‑critical zones.

Blend approaches: use proportional for non‑critical trim and secondary seams; controlled for primary seams and articulation.

Ease budgets that scale

Wearing ease should scale modestly; design ease may scale differently to maintain the same silhouette read across sizes. Example: to keep a “boxy guard jacket” boxy, larger sizes may add slightly less design ease than smaller ones to avoid ballooning at distance. Define per‑zone targets: torso +X cm, seat +Y cm, knee/elbow +Z cm per grade step.

Concept cue: In orthos, annotate ease bands at underarm, seat, and knee per size, not just overall circumference.

Darts across sizes: intake conservation and migration

The total dart intake set by a sloper changes with body shape, not merely with size. As grades increase, bust or seat intake may rise while waist darts reduce for straight body types. Specify which seams absorb intake changes: princess seams can carry more intake on fuller bodies, while yokes can level visual lines without adding bulky darts.

Rule: Keep dart endpoints aimed at plausible landmarks (apex, pivot points). On leather or laminates, split growing intakes into extra panelization rather than deep single darts.

Anchor points that must not drift

Lock these to prevent animation and readability issues:

  • Neckline depth and CF/CB: keep CF/CB straight; allow neckline width to grade minimally so collars fit rigs.
  • Armhole notch and sleeve cap balance points: preserve pitch so sleeves hang correctly across sizes.
  • Crotch length and curve balance: deepen back rise more than front for larger sizes; keep intersection off stress hot‑spot if gusseted.
  • Knee and elbow positions: align to skeleton joints; grade circumference around, not the height to floor.
  • Motif carriers: rank bands, faction chevrons, piping offsets—either keep absolute width or define a rule (e.g., fixed 18 mm trim across all sizes; offset stays 25 mm from CF).

Panelization that grades cleanly

Design panels to absorb grade deltas predictably:

  • Vertical panels can widen without distorting iconography.
  • Princess seams can take extra intake for curvier sizes.
  • Side panels can expand quietly while keeping CF/CB clean for emblem placement.
  • Back yokes redistribute seat ease and keep pocket geometry stable. Avoid style lines that must cross multiple pieces at non‑orthogonal angles unless you nominate a master piece and allow neighbors to “follow” during grade.

Sleeve and leg strategies

  • Sleeve caps: Increase cap height gradually (+2–3 mm per size) and add circumference at biceps; keep pitch consistent. Two‑piece sleeves grade along front/back seams to maintain elbow articulation.
  • Legs: Pre‑curve increases slightly on larger sizes to match thigh mass and knee path. Grade inseam and outseam asymmetrically to preserve side seam hang.

Skirt and hem logic across grades

Straight skirts: distribute additional intake via waist darts and side seams; maintain slit/vent length relative to knee height, not absolute centimeters. A‑lines: push grade into panel flare to keep hem sweep proportional; circle cuts: maintain arc geometry—grade waistline while keeping bias balance so drape rhythm stays consistent.

Motif scaling and LOD

At gameplay distance, trim becomes bands of value. Define LOD rules:

  • LOD0–1 (close): full stitch/tape detail; trim width fixed in mm.
  • LOD2–3 (mid): baked normals; trim width relaxed but icon geometry stays aligned to seams.
  • LOD4+ (far): convert to simple value bands; keep angles and placements. Ensure motifs don’t crawl across sizes; if they must scale, scale with the panel they live on, not globally.

Texture and print scaling

All‑over prints can moiré or break at seams. Tie repeat scale to size buckets (S/M/L) rather than per‑size increments, and anchor motif centers to CF/CB or pocket/yoke intersections. For decals, define clamp zones that never stretch (emblems, QR sigils); the surrounding panel absorbs grade.

Customization layers: sliders, swaps, and kit logic

NPC customization often mixes:

  • Body sliders (height, girth, proportion): tied to sloper families.
  • Garment variants (short/regular/tall; slim/regular/relaxed): swap block variants, not just scale.
  • Module swaps (collars, sleeves, pockets, knee patches): use standardized seam paths and notch positions.
  • Accessory fit (belts, harnesses): define anchor spacing (belt loops every X cm; harness D‑rings at fixed offsets from side seam) so parts port across sizes. Document compatibility matrices so the generator avoids illegal combos (e.g., tall body + short rise pants without crotch grade).

Mobility zones preserved

Across sizes, keep armhole‑to‑elbow, waist‑to‑crotch depth, knee‑to‑floor, and seat expansion consistent with rig joints. Increase circumferences and curve depths locally but do not move hinge heights. If outerwear stacks over base layers, bake cumulative ease targets per size (e.g., total elbow ease +4 cm at 90° flex) and redistribute among layers.

Climate, economy, and tech filters for grade policy

  • Climate: Cold regions tolerate more seams and quilting; hot regions reduce panel count and use vents/mesh zones. Grade vent lengths to remain effective (e.g., hot‑climate side vents maintain 20% of garment length).
  • Economy: Wealthy factions grade with curved, multi‑panel pieces; frontier factions rely on straight seam expansions and rectangular gussets for cutting efficiency.
  • Tech: High‑tech allows bonded micro‑intakes that grade invisibly; low‑tech externalizes intake into ties, gathers, and pleats that scale in count rather than depth.

Simulation and mockup proxies

Before prop‑ing a whole pool, validate on three sizes per height band (e.g., S/M/L Regular). Run sit, squat, reach, mount tests. Check collision at underarm, crotch cross, waistband, and knee. Adjust grade rules rather than per‑size hotfixes to avoid combinatorial bloat. Maintain a grayscale “grade sheet” render that overlays S vs L to confirm motif and seam coherence.

Handoff: callouts that de‑risk production

In your concept sheets, include:

  • Size grid and height bands with silhouettes.
  • Anchor callouts: what stays fixed (trim widths, offsets, hinge heights).
  • Ease budgets per zone across sizes.
  • Dart intake tables: total and distribution by size/archetype.
  • Panel map with IDs for sim and texture packing.
  • Compatibility rules for modules and accessories.
  • LOD trim policy and print scaling notes.

QA and heuristics for pools

  • “Does the insignia land in the same visual band across sizes?”
  • “Do sleeves hang with the same pitch from XS to XL?”
  • “Does knee patch stay centered over patella at walk cycle?”
  • “Are vents long enough to allow stride at all heights?”
  • “Do darts terminate at sensible landmarks after grading?”
  • “Does the silhouette read as the same class fantasy at distance?”

Common pitfalls and corrections

  • Uniform scaling of textures → Anchor decals to panels; clamp emblem stretch.
  • Trim that grows with size → Fix mm width; adjust offset if needed.
  • Crotch bind on larger sizes → Increase back rise length and curve depth; add seat panelization.
  • Sleeve twist after grading → Re‑balance cap vs armhole notches; preserve pitch; add biceps circumference.
  • Skirt slits flashing → Tie slit length to knee height; add modesty underlay for tall sizes.

Closing

NPC grading is worldbuilding math. By starting with multiple slopers, budgeting ease by zone, routing dart intake into grade‑friendly seams, and locking anchors that matter for motion and identity, you create a system that scales variety without chaos. Concept art that encodes these rules—visibly and in notes—hands production a toolkit, not a puzzle, and your NPC crowds will look intentional from XS to 4XL, from square to scope, across climates and factions.