Lesson 01 · Materials

How Surfaces Work

A materials lab for art, design, and intro materials science. Same shape. Different light rules.

In short

A surface finish is how a material returns light to your eye.

Low roughness looks like chrome, higher roughness looks like satin, metalness tints metal reflections, and clearcoat adds a glossy layer on paint.

A MatCap fakes the light with one stored image. PBR computes the light from the scene.

Time 20 min
You will learn why chrome and satin look different
Try first drag across the big chrome knot to see the real material
Core lesson MatCap fakes · PBR computes

Enter the lab ↓

What you will see

DiffuseLight scatters. Soft. No sharp mirror.
SpecularMirror lobe. Highlight shape = finish.
RoughnessMicro-facets spread the highlight.
MetalnessMetals tint reflections. Dielectrics keep white Fresnel.
ClearcoatExtra glossy layer over paint or lacquer.
AnisotropyBrushed grooves stretch the highlight.
MatCap · baked
PBR · computed

After the lab

Where you see this

These finishes are not only for demos. People in named jobs use the same ideas when they light chrome, satin, paint, and plastic for screens and stores.

  1. Film and game characters

    Look-development artist

    Look-development artists set how cloth, metal, and paint respond to light before final frames are made. They judge roughness, metalness, and clearcoat so a chrome buckle and a satin jacket stay believable when the light moves.

  2. Online stores and furniture catalogs

    3D product visualization artist

    Many product pages show digital models instead of studio photos, especially when one chair needs many fabric and finish variants. Visualization artists tune metalness and roughness so chrome legs look sharp and soft wood stays matte under store lighting.

  3. Car paint and trim in online builders

    Automotive CGI artist

    Online car builders show paint and trim as interactive 3D. Automotive CGI artists use clearcoat for lacquered paint and anisotropy for brushed metal so highlights stretch the way they do on a real panel.

  4. Product finishes before tooling

    Colour and material (CMF) designer

    CMF designers choose how a product will look and feel: gloss plastic, soft-touch paint, or metal. They review digital finish samples with the same ideas—roughness, metalness, and layered clear coats—before parts are made.

  5. Rooms and interiors for clients

    Archviz artist

    Architectural visualization artists place materials on walls, floors, and fixtures in room images. Correct roughness and metalness keep brushed steel railings and matte plaster from looking like plastic under soft daylight.

Check the idea

Common mistakes

These are common mix-ups. Each answer uses the same ideas as the lab.

Is MatCap the same as PBR?

No. A MatCap fakes light with one stored image. PBR computes light from the scene. Move the lamp, and only the PBR finish changes.

Does high roughness mean the object is dirty?

No. Roughness is how much the tiny surface bumps spread the highlight. A clean matte eraser is rough. A polished spoon is smooth.

Why do metals tint reflections?

A metal reflects some colors and absorbs others. The highlight takes the metal color. Paint and plastic keep a white highlight.

Does clearcoat replace the base color?

No. Clearcoat is a thin glossy layer on top of the color, like lacquer on a car. The paint color stays. The extra layer adds a sharper gloss.

Why does a MatCap ignore a moving light?

The light in a MatCap is already stored in the image. It does not read the lamp in the room. PBR reads that lamp each time.

For teachers

Short objectives, one classroom loop, and how the lab maps to studio practice and materials science.

Learning objectives

  • Name diffuse vs specular reflection on a real object.
  • Predict how roughness changes highlight size.
  • Explain why metals tint reflections and plastics do not.
  • Contrast MatCap (baked lookup) with PBR (computed lighting).

10-minute classroom activity

1) Hold a phone, a matte eraser, and a metal spoon under one desk lamp. 2) Students sketch highlight shape on each. 3) Open Specimen 02 and match roughness/metalness. 4) Finish on Specimen 04: write one sentence on why MatCap fails under a moving light.

Art & design map

Rendering look-dev, product design finishes, sculpture patina vs polish, concept art material callouts.

Materials science map

Surface roughness (Ra intuition), metals vs dielectrics, multilayer coatings (clearcoat ≈ lacquer), anisotropic machining marks.