Edge wear

Edge wear is the damage that collects on the exposed edges of an object: paint chipped off a metal corner, bare wood showing on the rim of a table, a steel step polished bright where boots land. Edges stick out, so they get knocked, rubbed and scraped first. Adding wear there is one of the quickest ways to make a surface look used and to show off its form, because a thin bright line catches the eye along every bevel.

It is also easy to overdo: a prop outlined in uniform silver scratches is a common beginner mistake.

#How edge wear is generated

Most edge wear starts as a mask: white where wear shows, black where it does not. The mask then blends a worn material (bare metal, raw wood) over the finished one.

The key input is curvature: a map that is light on convex edges, dark in concave corners and mid-grey on flat areas. Blender's Pointiness output describes the same idea per vertex: "Lighter values indicate convex angles, darker values indicate concave angles", which "allows you to do effects like dirt maps and wear-off effects" (Blender Manual: Geometry Node).

Painter's Metal Edge Wear generator shows the full set of inputs. It needs baked position, curvature, ambient occlusion and world-space normal maps, and exposes, among others (Substance 3D Painter documentation: Metal Edge Wear):

• Wear Level and Wear Contrast: how much wear, and how hard its border is.
• Curvature Weight: how much the edges drive the result. Adobe warns that "a very low Curvature weight can remove all edge wear, leaving only the grunge."
• Ambient Occlusion Masking: keeps occluded areas from receiving wear, since recessed edges are protected.
• Grunge Amount and Grunge Scale: the noise that breaks the mask up.
• Curvature Type: Standard (sharp), Sobel (slightly blurrier) or Smooth (blurred at several levels, which can lose detail).

A clean bake is therefore needed, because curvature artefacts become wear in the wrong places (see fixing baking artefacts).

#Four places to create edge wear

1. In the texture, from a generator. The common route for uniquely textured props, often as part of a smart material.
2. Painted by hand, on top of or instead of a generator, where the story puts it: handles, steps, the corner a door keeps hitting. See sculpting damage and wear for sculpted chips.
3. Baked into a trim sheet, so every asset that uses the trim inherits the wear along its bevels. See trim sheets.
4. In the shader at runtime, from vertex colour, a mask or curvature computed on the fly, which lets the same mesh be clean in one place and worn in another. See vertex painting and blending and material layers and Substrate.
5. On edge strips of geometry, so-called edge decals or geodecals: thin strips along the bevels that carry a chipped-edge texture from a shared sheet.

Runtime edge detection is possible too. In a Polycount thread, Obscura shared an Unreal material function that finds edges "in realtime" on meshes with bevelled edges and face-weighted normals, removing the need to bake curvature, but noted it "suffers from strong aliasing at distance" (Polycount: FWVN edge wear material function for dynamic…).

#How to make one

The steps below add chipped paint to a painted-metal crate in Substance 3D Painter, using the Metal Edge Wear generator. The crate is about 1 m on each side, textured at 2048 × 2048 px.

1. Bake the mesh maps. The generator needs baked position, curvature, ambient occlusion and world-space normal maps (Substance 3D Painter documentation: Metal Edge Wear). Fix any fixing baking artefacts first, since a bad curvature bake turns into wear in the wrong places.
2. Set up two layers. At the bottom, a fill layer with the paint (colour, low metallic, medium roughness). Above it, a fill layer with the material underneath the paint: bare steel, which is metallic and shinier. See physically based rendering.
3. Mask the top layer with the generator. Give the bare-metal layer a black mask and add the Metal Edge Wear generator to it (Substance 3D Painter documentation: Metal Edge Wear). Bare metal now shows only on convex edges.
4. Tune the amount. Lower Wear Level until only the most exposed edges show metal, and raise Wear Contrast for a crisp chip border. Keep Curvature Weight high: Adobe warns that "a very low Curvature weight can remove all edge wear, leaving only the grunge" (Substance 3D Painter documentation: Metal Edge Wear).
5. Protect the recesses and break up the line. Turn up Ambient Occlusion Masking so occluded edges stay clean, then set Grunge Amount and Grunge Scale so the wear breaks into chips instead of a continuous outline (Substance 3D Painter documentation: Metal Edge Wear). On a 1 m crate, most chips should be a few millimetres to a couple of centimetres wide.
6. Paint the story. Add a paint layer to the same mask and paint wear in by hand where hands, boots and forklifts would hit, and paint it out on protected edges. Generators follow geometry, not use; Joost found it "a bit tricky" to get wear "to only appear in logical places" procedurally (Polycount: Agram 2000 SMG).
7. Check at gameplay distance. Wear that reads at 30 cm in Painter can turn into a bright outline at 10 m. Reduce it until the edges read without outlining the whole prop.

To reuse the result, save the layer group as a smart material.

#Video tutorials

#Use in recent games

• Concord (Firewalk Studios, 2024). Hugh Chew's Substance Painter library for the game's characters gives every smart material a Base folder and a Wear and Tear folder, and "most Smart Materials retain similar Wear and Tear features with small adjustments for specific details" (ArtStation: Concord - Smart Material Pipeline). Shared wear rules keep characters made by different artists consistent.
• The Last of Us Part I (Naughty Dog, 2022). Matthew Trevelyan Johns' trim pipeline replaced many uniquely baked props with shared baked-bevel trims (ArtStation: The Last of Us: Part I...Trim Pipeline). His captions note that the trim layouts "have all of the edge-wear and texture details as well as blend masks created for them", used through "re-usable trim shaders" (ArtStation: The Last of Us: Part I...Trim Pipeline). The wear is authored once per trim and reused by every asset mapped onto it.
• Star Citizen (Cloud Imperium Games, in open development). On Polycount in 2015, Johns described the Gladiator ship: a master material with sub-materials, and a secondary blend shader "controlled by vertex alpha" that was "great for achieving subtle wear and tear in areas of occlusion" (Polycount: Star Citizen...The Gladiator...ART DUMP). The ship was too big to bake uniquely, so wear came from shader blends over tiling textures rather than one painted texture (Polycount: Star Citizen...The Gladiator...ART DUMP).

#Related terms

smart materials · sculpting damage and wear · unique texturing · trim sheets · ambient occlusion · baking · vertex painting and blending · geodecals

#Further reading and watching