Sarah Clarity Studios

Chapter 1: Coatings & Finishes

Created by Sarah Choi (prompt writer using ChatGPT)

Coatings & Finishes for Mecha: Materials & PBR (Matte/Gloss, Stealth RAM)

Coatings and finishes are where mecha design stops feeling like “paint on a model” and starts feeling like an engineered object that lives in weather, heat, friction, solvents, and budgets. For concept artists, coatings are a readability tool: they separate functional zones, clarify massing, and sell scale. For production artists, coatings are a pipeline contract: they dictate shader complexity, mask logic, texture authoring, and how wear patterns will behave across LODs and lighting conditions. A “matte black stealth coat” is not one thing—it’s a layered system with a purpose, a failure mode, and a rendering signature.

A useful mental model is to think in stacks. Most real surfaces are not “a material,” they are a substrate (metal/composite/ceramic/glass), plus a prep layer (conversion coat, primer, adhesion promoter), plus a functional coat (corrosion barrier, thermal barrier, RAM, anti-fouling), plus a finish coat (color, gloss level, clearcoat), plus environmental contamination (dust, oils, soot), plus damage and repairs. In PBR, you’re not painting a single value—you’re describing the optical behavior of that stack: how it reflects (specular/roughness), how it absorbs (base color), how it micro-facets (roughness breakup), and how it changes with heat, time, and handling.

Finish language as a design tool

“Matte vs gloss” is often discussed like a style choice, but it’s really about micro-geometry and energy. Gloss reads as a smooth micro-surface: highlights travel, edges sparkle, curvature becomes legible. Matte reads as a rough micro-surface: highlights spread, values stabilize, silhouette and macro-form do more of the work. The same base color can look heavier or lighter depending on roughness, because the distribution of reflections changes the perceived contrast and edge sharpness.

As a concept artist, you can use finish language to control eye flow and hierarchy. Reserve higher-gloss or clearer highlights for “hero” surfaces—cockpit canopy frames, sensor housings, weapon shrouds, fresh replacement panels—because they catch light and guide attention. Use matte and semi-matte to reduce noise on large armor masses so the silhouette stays readable at distance. If your mecha has too many glossy surfaces, it can become a glittery blob under HDR lighting; if everything is dead-matte, it can read like unpainted clay and lose material separation.

For production, finish language maps directly to roughness ranges and breakup. “Matte” isn’t a single roughness value; it’s a distribution. A believable matte armor panel usually has subtle roughness variation: slight streaking from manufacturing directionality, faint mottling from pigment dispersion, and localized smoothing from handling. Your goal is to avoid “flat roughness” across large areas—flat roughness reads procedural and plastic unless the art direction explicitly wants it.

Metals: substrate, treatments, and the “painted metal” trap

Mecha loves metal, but not all metal should look like “bare steel.” Many operational machines hide their metal under coatings because corrosion and maintenance cost are ruthless. Bare metals are best used deliberately: high-wear edges that have polished through a finish, exposed fastener heads, piston rods, heat-stressed exhaust collars, or field repairs where the finish wasn’t reapplied.

For concepting, choose a metal family by behavior rather than name. A “structural” metal reads thick and cool, with slower dents and strong edge definition. A “thin sheet” metal reads as lighter gauge, with oil-canning, ripples, and faster deformation. A “machined” metal reads precise: sharp chamfers, consistent spec, fine anisotropy. Then decide if it’s treated: anodized (often for aluminum), passivated, phosphated, conversion-coated, or simply primed for paint.

In PBR, remember the core rule: true metals tint the reflection and have little to no diffuse base color (in metal/rough workflows, metallic=1 for metal areas). Painted metal is not “metallic paint” in the shader sense—it’s a dielectric coating on top of metal, meaning metallic=0 on the paint layer, with exposed metal only where the paint is chipped. This is the classic trap: concept art calls it “painted metal,” but a naive material setup makes the whole panel metallic and it becomes candy-like.

Composites: engineered roughness and edge behavior

Composites (carbon fiber laminates, glass fiber, aramid/Kevlar hybrids) are common in mecha fiction because they imply strength-to-weight and advanced manufacturing. Visually, composites often read through subtle weave cues, crisp edges with different failure behavior than metal, and coatings that can be semi-matte to satin.

For concept artists, composites are most convincing when you show their engineering constraints. Laminates like broad gentle curves and avoid tight radii unless the design suggests complex layups or 3D weaving. Edges may have protective caps, resin-rich zones, or bonded seams. You can also show “sandwich” construction—outer skins with a core—through chipped edges that reveal a lighter interior.

For production, decide whether the weave is a literal pattern (visible carbon) or a story cue that should be mostly suppressed by paint. Visible weave everywhere is flashy but often unrealistic for military or industrial mecha, and it can alias at distance. If weave is visible, treat it as a subtle normal detail and roughness modulation, not a high-contrast base color checkerboard. Many composite parts are painted or coated specifically to protect from UV and moisture, so the “raw carbon look” is a special-case aesthetic.

Ceramics: thermal, ballistic, and the “chalky” signature

Ceramics in mecha design can imply thermal barriers, radar transparency for sensor covers, or ablative/ballistic tiles. Visually, ceramics often have a “chalky” or powdery roughness, high resistance to small scratches, and different chipping: they fracture and spall rather than dent.

For concepting, ceramics can be a strong storytelling tool around heat. Put ceramic coatings or tiles around exhausts, weapon muzzles, and hot gas paths. Use segmentation (tiles, panels, sprayed zones) to show where the thermal problem is worst. If you want a Space Shuttle–like tile language, go heavy on seams and replacement patterns. If you want a modern thermal barrier coat (TBC) language, it’s more continuous, with subtle texture and a slightly different color cast.

For production, ceramics demand careful roughness and normal treatment. A ceramic tile surface can have micro-pitting, slight waviness, and seam darkening. Avoid making it too uniformly bright or it will look like plaster; avoid making it too glossy or it will look like enamel. If it’s a radar-transparent ceramic composite radome, it often reads smoother and more uniform than a thermal tile—different ceramic, different finish.

Glass: canopy optics, coatings, and readability

Glass in mecha is rarely “just glass.” Canopies and sensor windows often include laminated layers, anti-reflective coatings, conductive films for de-icing, HUD waveguides, tint gradients, and impact-resistant outer skins. As a concept artist, you can use glass to communicate pilot safety, sensor sophistication, and scale.

Finish choices on glass are mostly about controlling reflections and interior visibility. A glossy canopy with strong reflections hides the cockpit and can make the mecha feel sealed and mysterious. A slightly less reflective canopy (through coating cues or roughness micro-breakup) can reveal interior forms and give character. You can also use polarization-like banding, subtle iridescence, or edge tinting to suggest multi-layer coatings without going full “rainbow sci-fi.”

In production PBR, treat glass as a disciplined material: correct IOR behavior, thickness, and a deliberate approach to smudges and micro-scratches. Smudges should be localized to touch zones and maintenance access, not evenly spread. Wiper arcs, dust accumulation at edges, and tiny stone impacts are your realism levers.

Coating families and what they do to the look

A clean way to design coatings is by function first, look second. Anti-corrosion coats (primers, conversion coatings, sealers) are usually visually subtle but affect wear: they can show through chips as a different color layer, and they change how rust blooms. Anti-fouling and dirt-shedding coats change how grime sticks, often leading to cleaner panels with sharp dirt boundaries. Thermal barrier coatings shift color and surface texture in hot zones, sometimes with a soft, sandy micro-normal.

Then there are “signature” coats: stealth RAM, IR-suppressive topcoats, ceramic radomes, or conductive paints. These can be big art-direction anchors because they imply doctrine. A mecha designed for covert operations will bias toward low-sheen surfaces, minimal spec hits, and subdued color separations. A parade/hero unit might have higher gloss, crisp clearcoat, and intentional highlight choreography.

Stealth coatings and RAM: how to depict without making it magic paint

Radar-absorbent materials (RAM) in fiction are often reduced to “matte black,” but you can make the design feel more engineered by showing the system rather than the color. Many stealth signatures come from shape management, seams, and material transitions as much as any coating. For concept art, use coatings to support those cues: continuous surfaces where you’d want fewer discontinuities, controlled seam geometry, and deliberate edge treatments.

A stealth-oriented finish language usually includes low specular contrast, controlled highlight size (high roughness but not chalk), and minimal bright metal exposure. However, stealth does not necessarily mean “dirty matte.” A well-maintained stealth platform can look clean but subdued—matte with precision, not matte with neglect. You can imply RAM with panel gasket patterns, sawtooth seam edges, flush fasteners, and replaceable RAM tiles or patches that have slightly different roughness than surrounding paint.

For production PBR, RAM is mostly a roughness and normal story, plus subtle base color shifts. Consider building RAM zones as a material variant with slightly different roughness distribution and microtexture frequency. The biggest giveaway is overdoing it: if the surface becomes uniformly black and dead, it loses scale and looks like a rubber toy. Keep value and hue separation small but present. Let curvature and macro-form carry the read.

Matte, satin, gloss: the “finish triangle” for readability

Instead of thinking in two states (matte vs gloss), think in a triangle: matte, satin, and gloss each have a job. Matte is for mass and stealth, satin is for “real machine” believability, and gloss is for focal points and premium protection. A lot of modern equipment lives in satin because it balances cleanability, durability, and controlled reflections.

In concepting, assign finishes by interaction. Touch zones (handles, ladders, access panels) often become slightly glossier over time from oils and abrasion, even if the original coat was matte. High-flow zones (leading edges, knee/shin guards) might polish or burnish. Heat zones can become glossier from vitrification or duller from oxidation, depending on the material. Use these shifts to create story without extra greebles.

In production, define finish targets with ranges and variation, not single numbers. A “satin armor” might be a mid-roughness baseline with subtle mottling and directional streaking. A “gloss clearcoat” might have tight highlights but still needs micro-scratches and swirl marks in service-heavy areas.

Wear, repair, and the truth of layered finishes

The most convincing mecha finishes are not about adding random edge wear—they’re about consistent failure logic. Paint chips where impact occurs and where panels flex, not evenly along every edge. Abrasion happens where parts rub, where dust is trapped, and where maintenance tools contact surfaces. Thermal cycling causes discoloration, micro-cracking, and soot patterns that follow airflow.

For concept artists, wear is a readability and narrative device. Use it to show scale (micro-scratches vs big gouges), role (heavy combat vs ceremonial), and maintenance culture (clean and patched vs neglected and rusty). A single repaired panel with slightly different sheen can tell a story faster than ten bullets holes. If you’re designing a stealth unit, repairs might be more visible as mismatched RAM patches, but metal exposure might be rare because it’s operationally undesirable.

For production, wear needs mask logic and reusability. Think in layers: base coat wear, primer reveal, bare substrate reveal, then dirt/soot overlays. Use curvature and ambient occlusion carefully; they can help, but if curvature drives all wear it becomes a procedural cliché. Add authored story masks for key parts—knee guards, weapon mounts, access hatches—and keep the rest more subtle.

Depicting coatings across lighting and cameras

A finish that reads great in a neutral studio light can collapse under harsh sun or neon night lighting. Concept artists should test finishes mentally against multiple lighting conditions: strong rim light, overcast diffuse, interior hangar, and battlefield firelight. Matte surfaces can go too flat in overcast; glossy surfaces can blow out in sun. The best designs have a finish plan that survives these shifts.

Production artists should plan for engine realities: tone mapping, post-processing, and reflection probes will affect perceived gloss. If the art direction relies on ultra-subtle finish differences, confirm that they survive the game’s lighting pipeline and compression. Sometimes you must exaggerate roughness contrast slightly to preserve the intended read after post.

Practical finish recipes for mecha (concept → production translation)

A useful workflow is to create “finish recipes” that are consistent across the project. For concepting, you describe them in plain language with a small swatch sheet: base color, sheen, and wear notes. For production, you translate that into a small set of master materials and masks.

A heavy industrial armor recipe might be a satin polyurethane topcoat on a corrosion-resistant primer, with localized matte anti-slip patches on walkable areas. In PBR terms, that becomes a dielectric base with mid roughness, subtle breakup, and a secondary material for anti-slip that is rougher, slightly darker, and has a fine granular normal. A stealth armor recipe might be a low-sheen topcoat with RAM patch zones that have different microtexture frequency, minimal metal exposure, and repair panels that are slightly mismatched in sheen.

A heat-zone recipe could be a ceramic thermal barrier coat over metal, with soot and heat tinting that follows flow paths. In PBR, that’s a non-metallic ceramic material (metallic=0) with high roughness, micro-pitting normals, and a controlled gradient of discoloration.

A cockpit/sensor recipe could be laminated glass with AR coating, subtle edge tint, and localized smudges near maintenance access. In PBR, that means correct transparency/refraction, tight control of reflection intensity, and a mask-driven dirt layer.

Checklist mindset: questions that keep finishes grounded

When you assign a coating, ask what problem it solves. Is it resisting corrosion, shedding dust, suppressing IR, absorbing radar, reducing glare, or surviving heat? Then ask how it’s applied. Is it sprayed, brushed, dipped, baked, bonded as a film, or installed as tiles? Application determines seams, thickness, and failure modes.

Ask what the maintenance story is. Can field crews touch it up? Does it require a clean-room process? Is it patchable with tape-like RAM panels? Maintenance determines whether you should show scuffs, mismatched panels, and obvious repair boundaries.

Finally, ask what the camera needs. Does the mecha need to pop at gameplay distance? If yes, you may need a controlled amount of sheen contrast or spec highlights to keep form readable. Coatings are not just realism—they are gameplay legibility.

Closing: finish plans are part of the design, not decoration

In strong mecha design, coatings and finishes are not an afterthought. They are part of the machine’s doctrine, environment, and budget, and they help the viewer understand what is armored, what is hot, what is delicate, and what is serviced. For concept artists, build finish language as a deliberate tool: assign sheen to hierarchy, use material stacks to sell engineering, and keep wear consistent with function. For production artists, translate that language into reusable material recipes, mask logic, and controlled variation that survives lighting, LODs, and post-processing. When your finish plan is coherent, the mecha feels like it could step out of the screen and leave fingerprints on the world.