Chapter 2: Material Simplification & PBR Handoff

Created by Sarah Choi (prompt writer using ChatGPT)

Material Simplification & PBR Handoff — Style Systems: Stylized ↔ Realistic

Why Materials Are a Style Lever

In character production, materials carry as much style weight as proportion or silhouette. “Stylized” isn’t just bigger shapes—it’s also simplified material families, grouped values, and controlled edge behavior that keep reads clean under gameplay lighting. “Realistic” widens the bandwidth: more nuanced roughness, micro‑normal variation, and secondary scattering. The handoff from concept to production succeeds when your style grammar for materials is explicit, testable, and camera‑proof.

The Stylization Continuum for Materials

Think of materials on the same slider as proportion. On the stylized extreme, you’ll see compressed value ranges, limited hue palettes, and restrained microdetail. On the realistic extreme, physical plausibility dominates: energy‑conserving shaders, accurate Fresnel, and real‑world roughness ranges. Most projects pick a median, e.g., stylized shapes + PBR‑correct metals, or realistic anatomy + simplified cloth response. Define where you sit and what’s non‑negotiable (e.g., metals always use albedo ~0, color lives in F0 via tinting? or never tint metals at all).

Shape, Edge, Value, Palette: The Four Material Rules

Shape → Material Block‑In: Start with large forms. Paint materials as big, clean masses before you add trim. If the thigh plate is “painted steel,” that’s one value group and one roughness family, not a patchwork of gradients.

Edge → Break Logic: Edges announce material transitions. In stylized systems, you’ll use bigger, cleaner bevels and limited highlight sizes; in realistic systems, you layer micro‑chamfers and breakups (nicks, rolled edges, wear) that respect manufacturing logic. Define bevel denominators (e.g., 2/6/18 mm) and where edge wear is allowed (outward corners, contact points) vs forbidden (random surface centers).

Value → Grouping First, Detail Second: Value grouping determines readability under desaturation. Stylized: keep albedo stacks tight, push separation in roughness. Realistic: allow broader albedo range but clamp extremes to avoid TV‑black/clip white. Ensure silhouettes survive as a two‑ or three‑step grayscale at 128 px tall.

Palette → Material Families: Lock each family (skin, hair, cloth, leather, metal, plastic, emissive) to a narrow hue/temperature band per faction. If “Lightning” is cool‑leaning, metals tilt cyan in specular, leather toward slate; “Fire” leans amber/copper. Avoid rainbow micro‑accents; reserve accent hues for focal zones.

Material Family Playbooks

Skin: Define melanin rails and undertone families (warm, neutral, cool). Stylized: low pore frequency, broader subsurface radius, painterly AO at nasal base and eye socket; Realistic: pore‑scale normals, micro‑sheen on T‑zone, tighter SSS. Provide masks for: melanin, vascular (blush), oil zones, stubble.

Hair/Fur: Stylized: clump‑based cards with simplified anisotropy direction maps; Realistic: multi‑spec lobes (primary/secondary), tinted transmission, per‑strand roughness variation. Deliver a comb/flow map and clump hierarchy diagram.

Cloth: Split by weave (plain, twill, knit) and fiber (cotton, wool, synthetics). Stylized: minimal weave normals, readable fold AO; Realistic: micro‑fibers, fuzz/sheen lobe for velvet. Define roughness rails per cloth type (e.g., cotton 0.55–0.7, leather 0.2–0.4 when clean).

Leather: Stylized: broad value steps, sparse grain; Realistic: pore/vein normals, subtle color breakup, edge burnish masks. Supply a wear progression strip (new → broken‑in → distressed) with roughness evolution.

Metal: Never paint color into base‑color for metals; keep albedo near black and drive look with metalness (1.0) and roughness. Stylized: capped highlight size, simple cavity darks; Realistic: anisotropy where manufactured (brushed steel), edge micro‑nicks aligned to use. Provide a metal roughness chart per alloy (aluminum smoother highs vs cast iron rough lows).

Plastics/Composites: Stylized: flat albedo, gentle roughness gradients; Realistic: subsurface tint for ABS, micro‑scratches in tangent space consistent with handling.

Emissives: Set nit caps and color lanes to avoid UI/VFX confusion. Define bloom thresholds, forbidden hues per faction, and “distance falloff” so glows don’t wash albedo in close‑ups.

PBR Basics You Must Lock Early

Pick a workflow and stick to it: Metal/Rough (ORM packing) or Spec/Gloss. Document packing conventions:

  • ORM Map: R = Ambient Occlusion, G = Roughness, B = Metalness (A = optional masks).
  • MRAO Variants: If engine expects MRA, state it clearly.
  • Spec/Gloss: Provide F0 values per dielectric (~0.02–0.08 sRGB), gloss = 1 − roughness.

Define linear vs sRGB sampling per map, and list gamma expectations. Lock unit scale and texel density targets (e.g., 512 px/m for LOD0 characters) so microdetail frequencies are consistent across the cast. Publish LOD rules for normal and roughness down‑res.

From Concept Paint to PBR Truth: The Translation

Concept paint looks great; PBR needs numbers. Bridge them:

  1. Material Reference Spheres: Include a 7‑ball strip on every sheet: matte dielectrics (roughness 0.8/0.6), mid plastic (0.4), glossy plastic (0.2), metal rough (0.6), metal mid (0.4), metal glossy (0.2), lit by the project HDRI.
  2. Roughness Rails: For each family, supply a two‑stop range and three presets (Clean / Used / Worn).
  3. Microdetail Library: Provide tileables for pores, weave, scratch orientations, fuzz—named and versioned.
  4. Numeric Callouts: Annotate key zones with roughness values (0–1), metalness (0/1), SSS radius in mm (skin), sheen intensity (cloth), clearcoat weight (automotive paint).
  5. Edge Policy: Where does paint chip? What never wears? Include a curvature‑to‑wear mask logic.

Bake Map Expectations and How Concepts Can Help

Downstream baking relies on consistent high→low decisions.

  • Normals: Show intended edge hardness and bevel sizes in concept linework. If stylized, clarify whether bevel is visual only or modeled.
  • AO: Provide a contact‑shadow pass in concepts to indicate grounding; specify if AO should be multiplied into albedo (usually no) or used purely in shading.
  • Curvature/Thickness: Call out where curvature‑driven wear is allowed. For subsurface (ears, nose tip, fingers), provide a thickness guide to drive SSS.
  • ID Masks: On the sheet, include a simple color‑ID blockout of material regions for texturing splits.

Readability Under Gameplay Lighting

Ensure materials decode under the game’s LUT and exposure. Test your sheet under: key light only, overcast, night/blue hour, and VFX‑heavy scenes. In stylized projects, move contrast into roughness while keeping albedo flatter; in realistic projects, distribute contrast across albedo, roughness, and normal—but never let any single channel carry all the read. Provide a grayscale audit strip (albedo only) to confirm value grouping.

Edge Behavior: Highlights, Fresnel, and Wear

Edges are where style shows. Stylized: big, stable highlights with minimal sparkle, wide bevels, and painterly wear masks—often hand‑painted to support shape language. Realistic: highlight size tracks roughness, Fresnel rises at glancing angles, micro‑scratches align to use. Lock highlight size caps per material so promo renders don’t drift from in‑engine look.

Palette Discipline for Materials

Color belongs to materials, not just costumes. Tie palette to families: skin warms, metals neutral/cool, cloth controlled accents. Provide HSV bounds for each family to stop “palette creep” across the cast. Use temperature asymmetry (warm face, cooler outfit) to steer attention; never spread accent hues evenly—cluster them at focal zones (head/hands/insignia).

Trim Sheets, Decals, and Reuse

For production efficiency, define trim sheets for belts, seams, and panel trims. Stylized trims: bold, even widths, limited micro‑bevel; Realistic: varied flange and gasket profiles. Provide a trim usage map with world‑unit widths and intended roughness. For story detail, move logos, dirt, and serials into decals so reuse stays clean.

Skin, Eyes, and Teeth: High‑Sensitivity Zones

These sell life and uncanny valley risk.

  • Skin: Deliver a face mask pack (T‑zone oil, blush, stubble, melanin). Annotate SSS radius in mm, oil sheen targets, and wrinkle normal intensity for expression poses.
  • Eyes: Lock cornea IOR and roughness caps; define iris saturation range per style. Provide a catchlight policy (single key vs dual) so highlights don’t fight the value plan.
  • Teeth: Avoid paper white; set off‑white albedo and higher roughness near gumline. Stylized teeth simplify cusps; realistic retain subtle translucency.

Handoff Checklist (Put This on the Sheet)

  • Material callouts with labels tied to a numbered legend (skin, leather, cloth, metal types, plastic, emissive).
  • Numeric rails for roughness/metalness/spec/SSS/sheens and any clearcoat.
  • Reference spheres rendered in the studio HDRI.
  • Palette strip with roles: base, shadow, accent, emissive, dirt/blood overlays; HSV bounds annotated.
  • ID mask thumbnail for material regions.
  • Edge map indicating bevel sizes and allowed wear.
  • Grayscale audit (albedo only) at 128 px height.
  • Camera tests: FPP hands close‑up and TPP mid‑shot crops.
  • LOD/TD targets: texel density per body region; microdetail frequency notes.

Collaboration Notes by Discipline

Concepting Side: Deliver big‑shape material reads first. Avoid over‑texturing paint‑overs; show two passes—clean “factory” and “in‑world.” Include a mini‑lib of tileables and mask logic for texturing.

Production Side: Enforce numeric rails, keep ORM packing consistent, and validate under final LUT. Flag deviations during lineups; if concept pushed edge wear outside policy, request a corrective paintover.

Common Pitfalls and Fixes

  • Albedo Pollution: Color baked into metal albedo—fix by moving hue into spec/roughness behavior and reflections.
  • Micro‑Noise Everywhere: When every surface has equal frequency, TAA eats the read—fix with frequency zoning and roughness grouping.
  • Specular Overload: Unclamped highlights that break energy conservation—fix by capping F0 for dielectrics and using clearcoat for “pop.”
  • Inconsistent Texel Density: Patchy crispness—fix via TD audits and shared trim sheets.

Practice Drills

  1. Rebuild one hero with three material styles: Stylized‑flat, Median, Realistic—keep shapes identical, change only albedo/roughness/microdetail.
  2. Create a roughness only sheet; aim to read material families without color.
  3. Produce a wear map from curvature + manual masks; iterate until edge story matches gameplay touchpoints.

Final Thought

Material simplification is not the enemy of richness; it’s the architecture that lets richness land where it matters. When shape, edge, value, and palette rules drive your PBR handoff—and numbers back your paint—you get characters that look intentional in every shot, in every engine, across the entire pipeline.