Chapter 1: Modular Sets & “Breakup” Logic

Created by Sarah Choi (prompt writer using ChatGPT)

Modular Sets & “Breakup” Logic

Optimization, Modularity & Reuse for Prop Concept Artists (Prefabs, Kits, LOD Thinking)

Modularity lets small budgets look big. The same few meshes—if designed with the right proportions, pivots, materials, and decals—can build entire scenes while staying performant across platforms. This article equips both concept and production artists to plan prefab‑ready props, reusable kits, and deliberate breakup logic so content scales without visible repetition. We’ll frame modularity as a design language, not only a technical tactic.

1) What “modular” really means (beyond rectangles)

A modular set is a family of interoperable parts (geometry pieces, materials, and decals) that assemble into many believable variants. Good modulars share:

  • Shared metrics: common grid, unit scale, and snap rules.
  • Connection standards: repeatable joint types (slots, rails, flanges, clamps) with clear visual cues.
  • Variant levers: colorways, material swaps, trims, decals, and add‑ons that create diversity without new meshes.
  • LOD & impostors: planned simplification paths for distance.

From concept, treat each piece as a prefab node with known inputs/outputs, not a one‑off sculpture.

2) Start with metrics: the invisible rails

Grid: Pick a primary module (e.g., 10 cm or 0.5 m). All dimensions are multiples of this.

Snap origin: Place pivots at logical attach faces (corner, mid‑edge, center of mass) and ensure transforms are clean (no shear/negative scale).

Clearance & overlap: Decide tolerances (e.g., +2 mm gap for panels, 5 mm overlap for trims). Draw them on the concept sheets so modelers don’t guess.

Angle system: Prefer orthogonal + 45° families for broad reusability; if using curves, keep shared radii (R20, R40, R80) across parts.

3) The modular kit blueprint (concept deliverable)

Design the kit as tiers that combine top‑down and side‑on logic:

  • Tier A — Cores: chassis, frames, housings (carry silhouette & function). 2–4 pieces.
  • Tier B — Ports & Doors: hatches, drawers, lids, clamps (interaction focus). 4–6 pieces.
  • Tier C — Services: cables, ducts, rails, mounts (connect spaces). 4–8 pieces.
  • Tier D — Faceplates & Trims: lengths, corners, caps, brackets (repeaters). 8–12 pieces.
  • Tier E — Greeble Packs: bolts, vents, labels, stickers (micro variety). Decal/trim‑sheet driven.

Each piece ships with: name, footprint, pivot, attach faces, connection type, LOD notes, and breakup states.

4) Connection language (what makes kits feel engineered)

The fastest way to break repetition is to make joins legible. Pick 1–2 archetypes and reuse them relentlessly:

  • Bolt/Flange: visible fasteners, gasket seam; communicates serviceability.
  • Dovetail/Rail: sliding channels with stop blocks; ideal for swappable modules.
  • Mag‑Latch/Clamp: over‑center levers, spring seats; great for gameplay interactions.
  • Cable/Conduit: standardized collars (M20/M40), strain reliefs, and clips.

In concept, diagram each joint in orthos + a 3/4 hero and call out male/female parts and allowed rotations (0/90/180°).

5) Breakup logic: how to hide repetition on purpose

A. Geometry breakup

  • Provide A/B/C silhouettes for repeating units (e.g., three cap styles, two end plates, one asymmetric).
  • Add phase‑shiftable elements: vents with alternating fin counts (7/9), bracket hole patterns (2/3), offset cable loops.
  • Include negative space breaks: every Nth panel has a window, notch, or relief.

B. Material breakup

  • Author a trim sheet with 6–10 swatches (painted steel, brushed, rubber, ceramic, raw cast).
  • Create grime masks with controllable intensity and clean halos around decals/hazard bands.
  • Define edgewear zones that vary by orientation (top edges brighter, underside darker).

C. Decal breakup

  • Build a decal atlas: serials, barcodes, caution glyphs, inspection stamps, tape tears.
  • Provide location rules (e.g., left‑aligned to hinges; never cross panel seams) and randomization seeds.

D. Temporal breakup

  • Optional VFX hooks: blinking pips, steam vents, tiny fans. Temporal variance prevents copy‑paste feel.

6) LOD thinking baked in (near → mid → far)

Design pieces with a planned simplification ladder:

  • L0 (near): full bevels, perforations, small fasteners. Fine decals, micro normals.
  • L1 (mid): merge perforations into slotted louvers, reduce bolt counts, thicker decal strokes.
  • L2 (far): remove sub‑greeble; keep silhouette chamfers, bold color fields, and one glyph. Consider impostor cards for emissives.

On concept boards, show L0/L1/L2 side‑by‑side for a representative subset of the kit.

7) Prefabs & assembly patterns (how levels get built)

Define prefab recipes:

  • Linear: rail → segment → endcap; lengths in 1×/2×/4×.
  • Grid: panel → corner → interior → door; n×n arrangements.
  • Radial: hub → spoke → rim; 30°/60° increments.
  • Stacked: base → riser → topper; height variations.

Provide assembly diagrams with callouts for pivot placement, rotation limits, and collision envelopes.

8) Texel density, trims, and UVs (the performance triangle)

  • Texel target: define a baseline (e.g., 512 px/m for props, 1k px/m for hero faces). Keep kit parts within ±10%.
  • Trim sheets: allocate strips for common edges, bolts, and panel lips so many meshes share one texture.
  • Unique vs shared: reserve unique UV islands for branding/hero decals; everything else pulls from trims/atlases.
  • MIP safety: design decals with thick strokes and keylines to survive downsampling.

9) Instancing, draw calls, and material budgets (design for the engine you have)

  • Prefer one master material with parameter sets (color, roughness, grime amount) over many separate materials.
  • Group meshes to benefit from hardware instancing (HISM). Keep mesh variants minimal and driven by decals/materials.
  • Agree on budget heuristics early: max materials per prop (≤2–3), draw calls per prefab, and triangle targets by LOD. Note them on the concept.

10) Damage, wear, and swap‑outs (stateful modularity)

Design damage as modular swaps, not texture only:

  • Break kits: alternate endcaps, bent brackets, missing panels; a few “broken” parts refresh entire sets.
  • Fracture maps: predetermine break lines at seams and fastener rows.
  • State decals: scorch, tape, hazard stickers with opacity and hue controls for variety.
  • Repair logic: visible patch plates and rivet rows that obey the same metric rules.

11) Authoring the kit sheet (your north star)

Your concept pack should include:

  • Exploded family portrait: all parts labeled with dimensions and pivots.
  • Connection spec: orthos and 3/4s showing joint anatomy, gasket colors, fastener sizes.
  • Material matrix: per part, list allowed materials and colorways (e.g., housing: painted or brushed; caps: rubber only).
  • Variant menu: legal combinations (A‑frame + B‑door + C‑trim), with 6–12 curated examples.
  • LOD board: L0/L1/L2 snapshots and what’s removed/merged.
  • Decal atlas & placement rules: icon sizes at three distances; no‑go zones.

12) Concept ↔ production handshake

For concept artists:

  • Design pivots and snaps visually; mark them on the page.
  • Use consistent naming: KIT_Grp_Part_Var (e.g., KIT_Panel_Corner_A).
  • Annotate merges: “L1 collapses 16 bolts → 4; louvers replace perforations.”

For production artists:

  • Preserve pivots and axis orientation; bake grid alignment into the export.
  • Implement param materials (color, wear, grime) and expose to level artists.
  • Build prefab blueprints with sockets; document allowed rotations/offsets.

13) Breaking the grid without breaking the kit (controlled chaos)

Repetition fatigue comes from perfectly aligned copies. Introduce controlled offsets:

  • Micro translation/rotation: ±0.5–1.5° or ±1–3 cm on placeables where believable.
  • Orientation rules: rotate cable clips 90° every third segment; flip A/B caps in alternation.
  • Color jitter: gentle HSV variation (±3–5%) in materials; heavier in grime masks.

Ensure all chaos respects collision and animation needs.

14) Kits for different camera modes

FPP: prioritize interaction faces and hand clearance; add mid‑scale features that hold up during motion blur.

TPP: bulk up silhouettes and corner keys; reduce tiny cut‑ins that vanish on a distant character.

Isometric: emphasize top information and single‑direction diagonals; minimize moiré‑prone grills.

VR/AR: use world‑space scale for decals and LEDs; keep blink rates ≤3 Hz; prefer physical join geometry over painted seams.

Marketing: create a Hero Build preset (thicker bands, simplified repeats, cleaner grime) for trailers and thumbnails.

15) Quick QA loop (same day)

  1. Assemble a 5×5 grid scene using only your kit; count visible repeats.
  2. Run distance sweeps (close/mid/far) and confirm L1/L2 swaps preserve the story.
  3. Toggle color‑blind modes; ensure shape and numerals carry meaning.
  4. Export a ** store thumbnail** and a 4K hero: both should read.
  5. Check draw calls and material count per instance; trim if over budget.

16) Case mini‑studies

A. Industrial Panel Kit

  • 3 panels (solid, window, vent), 2 corners (square, radius), 2 doors (hinge, slide), trims, bolts, and a decal atlas. With A/B/C caps and 2 colorways, level artists build 40+ believable cabinets.

B. Pipe & Conduit Kit

  • Straights 1×/2×/4×, 90° elbows (short/long), T‑junction, flange joints, hangers, inspection port. Decals for flow arrows and pressure codes; grime masks tied to “below joint” normals for leaks.

C. Storage Crate Family

  • Three footprints, common lid system (snap/inset/lock), handle variants, corner bumpers, label zones. Damage swaps (bent lid, missing latch) and sticker atlas enable narrative variety without new meshes.

17) Closing

Modular success is 80% planning and 20% art. When pivots, metrics, joints, trims, and decals are designed as a system—and when breakup logic, LOD, and prefab recipes are explicit—your small kit will build rich worlds, stay performant, and remain a joy for level artists to use. Treat every prop as a potential kit seed, and your content library will compound in value across projects.