PBR Texture Maps Explained: What Each Map Does
You have downloaded a scanned material and unpacked the archive. Inside are more than a dozen PBR map files, each with a cryptic suffix in its name: albedo, roughness, normal_gl, ao.
This article is a map of the territory. It explains what each PBR map does, what its file looks like, how the maps add up to a material, and which set you need for your task. Each map gets its own in-depth article; this one gives you the whole picture.
The general principle is simple. Each map describes one property of the surface and stores it separately from the others. The renderer takes them all together and calculates how the surface responds to the light in a particular scene. That is why the same set of maps looks right in sunlight, in a studio, and in a night scene.
Below, every map is shown on the same surface: a piece of an old wooden door with peeling blue-gray paint and a steel hinge. It has almost everything you find in real materials: wood, paint, bare metal, gaps, and chips.
How PBR Maps Combine Into a Material
The easiest way to understand the set is to build the material step by step and watch what each group of maps adds. The light and camera stay the same at every step.
First, only Base Color goes on the surface. The colors and the pattern are there, but the door looks like a printed photo: the grain, the chips, and the gaps between the boards do not catch the light, and the whole piece has the same sheen.
Next come Roughness, Metallic, and Normal. Now there is relief: every grain line and every chip edge is lighter on one side and darker on the other. The paint gets a soft satin highlight, while the bare wood stays matte. The screws and the worn edges of the hinge start reflecting like metal, but the paint on the hinge does not.
Height and Ambient Occlusion come last. The gaps between the boards, the edges of the chips, and the areas around the screws get darker and deeper, and only now does the material look like a photo of the sample.
This order is also useful for debugging. If a material looks wrong in your scene, switch the maps off one at a time and watch what disappears: it is the fastest way to find the one that is plugged into the wrong slot or read in the wrong color space.
Base Color
The surface's own color. A brick is red, an apple is green, the paint on the door is blue-gray.
The map answers one question — what color the object is — and nothing else. Highlights, shadows, and reflections of the surroundings do not belong in it: all of that comes from the scene and appears on its own at render time.
A Base Color file looks like a photo taken under even, diffuse light without a single shadow. On the door, you can see the boards, the chips, and the hinge, but not the volume: the gap between two boards is just a dark stripe of color. The bare steel on the edges of the hinge is light gray and neutral in this map.
For metals, the meaning is slightly different: there, this map sets the color of the reflection, which is why copper reflects with a reddish tint and aluminum almost neutrally.
Roughness
Roughness is the map of how sharp a reflection will be.
The easiest place to see it is a tabletop. On a lacquered area, you can make out the shape of a window; on a worn area, the same window blurs into a large bright spot. The wood is the same color and the light is the same — only the roughness has changed.
Zero on a Roughness map means mirror-smooth and a sharp highlight; one means a wide, blurry reflection.
The file is grayscale: the lighter, the rougher. On the door, the paint and the wood are mostly the same medium gray, around the middle of the scale; the worn wood and the chip edges are lighter, and the bare steel is darker because it is smoother. The pattern of the painted hinge matches the pattern of the paint on the boards: roughness depends on the material at the surface, not on what lies underneath.
Metallic
Metallic is a switch between two ways of reflecting light: metal or non-metal.
It is not a gloss slider. Gray Metallic does not make wood shiny — that is what Roughness is for. Intermediate values are needed mostly at the boundaries between metal and paint and for mixtures like dusty metal; gray Metallic over the whole surface is almost always a mistake.
There is an important subtlety: the map describes the top visible layer. A painted metal part is not metal, because the light interacts with the paint. But where the paint is scraped off, the metal shows up again.
That is why a Metallic file is almost always two-tone. On the door, it is black everywhere, including the painted hinge, and white only on the screw heads and the narrow worn edges where bare steel shows. If you mark the whole hinge as metal just because it is made of steel, the paint will render as tinted chrome.
Normal
Normal is the map of which way the surface faces at each point.
Thanks to this map, the shader lights up small bumps that do not exist in the geometry at all: the pores of a brick, the grain of wood, scratches. The mesh stays smooth, which saves polygons, and the light behaves as if the relief were real.
A Normal file is easy to recognize by its lilac-blue color: a flat surface facing straight at the viewer is stored as a color around (128, 128, 255). Slopes in one direction shift toward pink, in the other toward green. On the door, the most visible lines in the map are the edges of the boards and the gaps, while the grain and the chips show up as fine detail.
The silhouette gives a normal map away: the outline stays smooth.
Height and Displacement
Height is the map of how high the relief is.
Unlike Normal, these maps can actually move the geometry: then the silhouette changes too, and the bumps cast their own shadows. Displacement costs more and is not always needed: if a detail is small and does not affect the outline, Normal is enough.
A Height file is grayscale and soft: lighter is higher, darker is lower. On the door, the boards are light gray with gentle waves where the wood has warped, the gaps are dark lines, and the hinge and the screw heads are slightly lighter than the boards because they sit on top. There is no paint pattern in it: a thin coat of paint barely changes the height.
Ambient Occlusion
Ambient Occlusion is the map of how much a point on the surface is hidden from ambient light.
A deep gap receives less surrounding light, a bump receives more, and the map stores exactly that difference. It adds depth to the recesses where light has a harder time reaching.
It is not captured by the camera but calculated from the scan's geometry. That is why AO depends only on shape: on the door, the exposed boards are an even light gray, but not pure white; the gaps are noticeably darker; and small dark dots sit along the chip edges and around the screws. There should be no paint pattern in AO.
Opacity
Opacity is the map that tells whether there is a surface here at all.
It is needed for leaves, mesh fences, hair cards, and die-cut stickers — anywhere a rectangular polygon has to look like a complex shape.
The file is black and white: white means there is a surface, black means there is none, and the scene shows through the empty area. It is a cutout, not glass: transparency with refraction is described by other parameters. The door has no Opacity map; its surface is solid.
Emissive
Emissive is the map of the surface's own glow.
A phone screen, a lamp, an indicator light on a device. A surface with this map stays visible even when nothing in the scene lights it.
An Emissive file is in color and almost entirely black: only the areas that are not black glow. The door, like most scanned materials, does not need this map.
What's in a ScanWOW Set
The set above is what an engine expects. A capture measures slightly different quantities, so the downloaded archive contains maps that are not on the basic list.
| Map | What it does |
|---|---|
| Specular | The surface's specular response — what you observe under directional light |
| Specular Intensity | How strongly the surface reflects |
| Specular Tint | What color that reflection is |
| Glossiness | The same as Roughness, but on the inverted scale: one means smooth |
| SSS Amount | How much light travels under the surface and scatters there |
| SSS Color | What tint the light picks up along the way |
| Mask | UV mask: white marks the UV islands, black marks the areas with no UVs; for a material with transparency, an opacity map takes its place |
In the set, Base Color is called Albedo, and Normal comes in two versions, OpenGL and DirectX: take the one your engine expects. Roughness is in the set too, next to Glossiness — choose based on your shader.
The strength and the color of a reflection live in separate maps because they are separate properties. Plastic, wood, and stone have colorless reflections, and everything that matters is in the intensity. Metals are the opposite: it is the color that tells copper from aluminum. On the door, almost all of these maps are flat: only the bare steel on the hinge and the gloss of the paint make a visible difference.
The SSS pair is for materials that light noticeably passes through: skin, marble, wax, the flesh of fruit. Part of the light enters them, scatters, and comes back out nearby, already tinted, and without that they look like painted stone.
A set of PBR maps is not a material yet: the material is assembled from them in a specific application.
Which PBR Map Set Your Task Needs
You do not have to connect every map in the archive. The set depends on where the material is going and what the shader can do.
Game engine. Unreal Engine, Unity, and Godot usually take Base Color, Normal, Roughness, Metallic, and AO. The last three grayscale maps are often packed into one file, one per channel. Height is rarely needed in real time, mostly for parallax or tessellation on large-scale relief.
Web and AR. The core glTF and GLB specification stores Base Color, Normal, Occlusion, Emissive, and one shared map for Metallic and Roughness. Opacity lives in the alpha channel of Base Color, and Height is not part of the core specification.
Offline rendering and visualization. Here you can use the whole set: Height as true displacement for large relief, SSS for wax, marble, and skin. Render times go up, but the silhouette and the shadows from the relief are honest.
Specular/Glossiness shader. If your application works in this workflow, take Specular and Glossiness instead of Metallic and Roughness. Do not mix the two sets in one material.
For mobile devices, the set is the same as for an engine, but at a lower resolution and always packed: that saves both memory and texture lookups.
Less Common Maps
Everything above describes an opaque surface without coatings. A material with its own physics gets additional parameters: car paint has coat, a separate glossy layer over the paint; velvet has sheen, a soft glow along the edges of the pile; brushed metal has anisotropy, a highlight stretched in one direction; glass has transmission and ior.
There are also utility maps that are not physical properties at all. curvature and cavity mark convex and concave areas so that wear and dirt can be applied procedurally. An id map paints parts of a model in flat colors so they can be assigned different materials.
PBR Map Cheat Sheet
| Map | What it controls | What the file looks like | How to read it |
|---|---|---|---|
| Base Color | Surface color | A photo without shadows or highlights | sRGB |
| Roughness | Reflection sharpness | Gray: lighter is rougher | Linear |
| Metallic | Metal or not | Black and white | Linear |
| Normal | Surface direction | Lilac-blue | Linear |
| Height | Relief height | Soft gray: lighter is higher | Linear |
| AO | Occlusion from ambient light | Light gray, dark in recesses | Linear |
| Opacity | Whether there is a surface | White — yes, black — no | Linear |
| Emissive | Self-illumination | Black, colored where it glows | sRGB |
The “How to read it” column is the technical import setting for PBR maps: color maps store hues, the rest store numbers, and the engine needs to know which is which.
Read Also
FAQ
What Types of PBR Maps Are There?
PBR maps fall into three groups: basic, additional measured, and utility. Every engine expects the basic ones: Base Color, Roughness, Metallic, Normal, Height, Ambient Occlusion, Opacity, and Emissive. A capture adds reflection and subsurface scattering maps, and complex materials may also have coat, sheen, anisotropy, and transmission. Utility maps like curvature and id map are used for texturing, not for rendering.
What Is the Minimum Number of PBR Maps You Need?
An opaque surface usually gets by with four PBR maps: Base Color, Roughness, Metallic, and Normal. AO is added almost every time it is available, while Height, Opacity, Emissive, and SSS are added only when the object's physics calls for them. For a non-metal material with no bare metal, Metallic can be replaced with a single value of zero.
Why Use Height If You Already Have Normal?
A Normal map changes only the lighting; the silhouette stays smooth. Height can actually move the geometry, and then the outline and the shadows from the bumps change too. If a detail does not show on the outline, you do not need Height — Normal is enough.
Why Are There More Files in the Archive Than Properties?
Some files store the same property in different forms. Normal comes in two conventions, OpenGL and DirectX; Roughness and Glossiness are one scale running in opposite directions; and sometimes three grayscale maps are packed into one color file to save memory. For a particular engine, you take one form of each property from the set.
Do You Have to Connect All the Maps?
No. A set of PBR maps is chosen for the task and for what the shader can do: a game engine needs one set, glTF another, and offline rendering the fullest one. An extra map that the shader does not read only takes up memory.
How Is a PBR Map Different From a Regular Texture?
A PBR map is a texture that stores one physical property of a surface rather than a finished picture. A regular texture often contains color together with shadows and highlights, and under different light it looks wrong.
Can You Get PBR Maps From a Single Photo?
PBR maps from a single photo can only be approximate. In that case, the color, normals, and roughness are not measured but guessed from the image, and on a different material or under different light, the guess drifts away from reality.
Sources
- Khronos Group. glTF 2.0 Specification: Materials.
- Adobe. Substance 3D Painter: Shader API, channel parameters.
