Chapter 1: Slot Systems & Dependency Maps

Created by Sarah Choi (prompt writer using ChatGPT)

Slot Systems & Dependency Maps for Character Concept Artists

Why slots and dependencies matter

Slot-based customization is how modern character pipelines expose choices to players while keeping models and materials performant and consistent. A slot is a reserved interface for content—head, hair, chest, legs, hands, feet, backpack, decal channels, palette channels—each with constraints for geometry bounds, rig attachment, materials, and UI logic. A dependency map describes how a change in one slot propagates to others: a tall hairstyle may require collar clearance; a hood disables high-volume hair; a faction palette remaps emblem inks; a face mask changes hairline reveals. For concept artists, understanding these contracts lets you design parts that are interchangeable, readable across cameras, and safe for production without guesswork.

Mental model: base, slots, and rules

Think of the character as a base body with guaranteed landmarks, a slot grid with allowed attachments, and a rulebook that governs compatibility. The base gives skeletal proportions, skin weights, and collision primitives. The slot grid defines where new geometry can live, which bones or sockets it follows, and what silhouette volume budgets it cannot exceed. The rulebook encodes dependencies: mutually exclusive states (hood up vs. big hair), priority masks (helmets override earrings), and material budgets per LOD. As a concept artist, you are designing both the individual parts and the rules implied by their shapes, closures, and palettes.

Heads: facial options, morphs, and read hierarchy

Head slots typically include face mesh variants, blendshape sets, facial hair, eyewear, masks, and headgear. The dependency map starts with read hierarchy: the eyes and mouth must remain readable under any combination. Concepts should establish safe eyeline windows—areas of the brow, cheek, and nose that remain uncovered in non-armor states—plus mask overlap margins that predict deformation around nasolabial folds and jaw rotation. When proposing face morph sets, sketch neutral, phoneme, and expression ranges as envelopes rather than fixed poses; note which accessories occlude those envelopes. If a respirator rides high on the maxilla, call out reduced smile range and whether the mask requires an alternative mouth blendshape. If certain face paints cross UV seams, call out a dedicated tattoo/facepaint material with its own atlas region to avoid stretching across eyelid UVs.

Hair: volume classes, collision, and hood logic

Hair is the most common failure point in modular systems. Establish volume classes—buzz/short, close bob, shoulder, long, extreme—and pair each with collision expectations: short hair coexists with high collars and helmets; shoulder hair must fork around pauldrons; long hair requires physics proxies and braid/cloth toggles. In concepts, paint collision silhouettes against torso and headgear contours to show expected resting states and motion arcs. Provide hood logic: which hairstyles auto-collapse into an under-hood variant, which disable the hood, and which swap to a tied-back state. If the game supports hair accessories as separate slots (bands, pins, beads), show how they anchor to guide curves or hair cards and whether they inherit hair color or use an accessory palette channel.

Outfits: garment layers, anchors, and breaklines

Outfit systems succeed when layers are planned around anchors (belt loops, grommets, epaulette posts) and breaklines (where one garment hands off to another). Define a layering policy in your callouts: base layer (undersuit/soft), mid layer (shirt/vest), outer layer (jacket/armor), plus specialty layers (cape, harness, backpack). For each, paint the occlusion zones and specify attachment points with small icons (snap, buckle, tie, magnetic, sewn) so production knows which pieces are rigidly parented versus simulated. Use trim zones—thin bands along hems, cuffs, and plackets—that act as style carriers across variants. In dependency terms, a bulky outer sleeve may force glove cuffs to thin; a tactical harness may reserve chest real estate that disallows giant medallions; a backpack may consume spine sockets used by capes. Your concepts should visualize these tradeoffs as compatibility overlays—transparent silhouettes layered over the outfit to demonstrate slot claims.

Palettes: channels, remapping, and faction identity

Color is a slot, too—typically implemented as palette channels (primary, secondary, tertiary, metal, accent, skin/hair) that map to material parameters. Your job is to:

  1. Propose a default palette per costume set that aligns with faction identity and class reads.
  2. Show remap sheets: one page per palette variant with the same render, only channel-swapped. Annotate which materials are color-locked for diegetic reasons (safety orange, medic white) and which inherit from the user’s chosen palette.
  3. Define value rails per channel—acceptable value/contrast ranges that preserve readability under global lighting and at LOD distances.
  4. Provide accessibility notes for color-vision diversity: avoid key reads that rely solely on red/green; strengthen form and pattern carriers. Dependencies arise when palette swaps must keep emblem legibility and dye coherence. Metallic inks shouldn’t adopt skin tones; AO and curvature layers remain neutral; emissive trims use separate intensity maps. Include a small palette LUT preview with swatches labeled to channels to aid shader authoring.

Decals: materials, masks, and wear logic

Decal slots handle emblems, numbers, names, kill marks, dirt, and sponsor patches. Define legal surfaces (flat panels, chest plates, shoulder tabs) with UV-safe regions. Provide mask shapes that gate decals to pre-approved zones, and specify blend modes (albedo-only for fabric patches; albedo+normal for embossed leather; emissive for neon signage). Show wear logic: decals inherit edge wear and grime from base materials or use a layered damage mask; high-friction areas like knees fade decals faster. If the game features user text, propose font guidelines and character limits to protect readability in localization. In dependency maps, decals must not collide with seam trims, zipper paths, or armor buckles. Show example conflict resolutions: shift tab location, reduce scale, or disable specific decal groups when certain armor pieces equip.

Building the dependency map: from beats to matrices

For maintainability, turn narrative and gameplay beats into a compatibility matrix. Start with a list of slots: Head, Hair, Face Cover, Eyewear, Headgear, Chest, Back, Arms, Hands, Legs, Feet, Cape, Harness, Decals, Palette Channels. Down the side, list volume classes or style families: Slim, Standard, Bulky; Formal, Tactical, Rugged, Ceremonial. Populate cells with allow, allow with swap, or disallow, and point to the swap variant (e.g., “Hair_Long → Hair_Tied,” “Cape → Cape_Slit”). Pair this matrix with flow diagrams that show state changes across beats: Act I hood down; Act II storm → hood up; Act III ritual helm → hair disabled; Finale medal ceremony → cape enabled, armor slim swap. These diagrams communicate to production which animation states and material swaps need triggers, and to design which UI locks appear when players equip certain combinations.

Heads & hair: portrait and camera tests

Concept coverage must include portrait tests (UI mugshots, dialogue close-ups) and in-game camera tests (FPP hands, TPP shoulder cam, isometric). Render each head/hair combination at the target FOV and distance to validate silhouette read and eye-line clarity. For hair, show wind/off-axis motion with arrows or small thumbnails that predict physics. If hair cards may intersect armor, illustrate a trim fallback—shortened strands or tucked braids—and note the LOD at which transparency is culled to solid geo.

Outfits & palettes: progression arcs without reauthoring everything

Use wardrobe arcs to deliver emotional progression while reusing systems. Early game: soft silhouettes, breathable fabrics, lower metalness, optimistic palettes. Mid game: reinforced joints, added harness nodes, palettes deepen, accents increase. Late game: hero trims and emissive reads, but keep base slots intact so the same undersuit works under multiple armor sets. For each arc step, call out which parts are new models versus kitbashed from earlier parts and which are merely palette or decal swaps. This protects scope and helps production forecast texture atlas impacts, since palette swaps ride existing materials.

Decal strategy across beats

Treat decals as storytelling carriers layered on top of a stable uniform. Early: clean emblems and low grime. Crisis: emergency markings, warning tape trims, and equipment serials appear; faction sigils grow in contrast. Resolution: commemorative patches and subtle prestige foils. Note which decals are diegetic UI—QR codes, AR fiducials, rank chevrons—and which should never be occluded by straps or capes. Tie wear masks to environmental biomes so dust vs. salt vs. soot drive different edge wear on the same decal slot.

Authoring constraints: LOD, atlases, and budgets

Every slot adds draw calls and memory. Mark material budgets per slot (e.g., hair: 1 material, 2–3 textures; chest armor: 2 materials max if emissive is separate). Note atlas responsibilities: small accessories and fabric trims should live on a shared kit atlas, while hero chest plates may justify a dedicated sheet. For decals, plan channel-packed masks (roughness/metalness/AO) so palette swaps don’t multiply texture count. In the concept, include a tiny budget box per board with expected triangle ranges, material count, and LOD silhouette notes. Even rough numbers help production and keep designs honest.

Rig & physics dependencies

Slots must honor rig and simulation. For headgear, include jaw and neck rotation envelopes with dashed arcs; if a collar blocks head pitch, that’s a dependency that needs either a rig limit or a collar redesign. For hair and capes, paint proxy volumes the physics team will approximate; skinny ribbons may be forbidden below a minimum width to prevent jitter. If gloves include long tassels, specify whether they are rigid, secondary bones, or cloth; each path implies different costs and dependencies on animation clips.

UI & UX: exposing the rules to players

Clear systems make happy players. Your dependency map should translate into UI rules: grey-out incompatible slots with concise reasons (“Hood disables big hair”), auto-suggest swaps (“Switch to tied hair?”), and preview palette effects on decals before commit. Provide mockups of paper doll layouts with slot names that match your concept labels, and design error-proof silhouettes—if a helmet requires a thin collar, the store tile should preview the equipped state to avoid surprise clipping. Include naming conventions that communicate size and compatibility (e.g., “Jacket_Bulky_A,” “Cuff_Slim_C”).

Production handoff: what to package with your concepts

With each concept set, include: a slot map (front/back/side orthos with slot outlines), a compatibility matrix, palette remap sheets, decal legal zones, budget boxes, and a beat flow diagram. Export layered PSDs with masks aligned to probable UV shells to speed baking of palette channels and decals. Include a short readme paragraph per set that states the rules in plain language so design, tech art, and UI can implement them without reverse engineering the boards.

Common pitfalls and how to avoid them

Most issues stem from unseen dependencies. Big hair under hoods, chin guards that block emotes, backpack straps that erase emblem reads, grenade bands that intersect jacket buttons, palette swaps that darken skin or metal beyond readability—each is preventable if the rules are visible in the concept. Always run a quick conflict pass: layer all variants atop each other at thumbnail size; any flashing edges or occluded reads are dependency flags. Where possible, propose an auto-swap solution rather than an outright disallow, because players value expression.

Closing: design for freedom inside constraints

Slot systems and dependency maps don’t limit creativity—they multiply it by making combinations reliable. When your concepts capture not only the look of parts but also the contracts those parts uphold, production can ship broader wardrobes with fewer bugs, and players can create expressive, coherent looks that survive every camera, biome, and beat. Treat slots as interfaces, design dependencies as readable rules, and your characters will scale from a single hero to an ecosystem of variants without losing identity.