For the layman – How 3D Rendering Works. Part 3: Textures

[ about a 20 min. read ]
Part 1: 3D models
Part 2: Materials & Shaders

In the previous article I talked about materials and shaders. The material is the main interface for the user that shows all the properties of the material that can be changed. The shaders contains all the algorithms and mathematical programming. Based on the material property settings, the shader determines the final look of the material. Now what I also briefly mentioned is that textures can further influence the material properties. What textures exactly are, how they influence the material properties and what some general texture types are, will be discussed in this article.

1. What is a Texture?

So what exactly is a texture. It is nothing more then an image file. Generally speaking, textures are often just straightforward jpeg image files, and are often also called maps.The textures are used to more accurately represent real world materials and their specific properties. For example the brown leather texture below is a Color texture which can be assigned to the color property of a material. The material will then have the exact colors from the texture when you render it in your 3D scene.

Brown leather, Color texture

Renderd on a 3D sphere model

We want this material to actually look more rugged like a real leather material. You can imagine that as it looks right now it is no way near that. It has the color of leather, but leather has more specific real world properties that makes leather look like leather. Like how reflective it is, or how different the highlights are in the leather skin folds. So we need to replicate these aspects. To achieve that in a 3D scene we will need more and different kinds of texture for the different properties of the material.

2. Different types of textures

To accurately replicate a material there are actually a few standard properties that normally only need to be tweaked with specific dedicated texture. These properties are:

  • Color – The color property of the material.
  • Roughness (the invers of Glossiness) – How sharp or blurry the materials surface reflections are.
  • Bump or Normal – Faking small surface imperfections like dents, scratches, lines, general coarseness of the material, etc.
  • Displacement – Actual surface relief of the material.
  • We will have a further look into the leather material, to see how by influencing the material properties with dedicated textures we can replicate a real world leather. Below is the overview of the textures we will use and for which property the texture is used.

    Color map

    Roughness map

    Normal map

    Displacement map

    Roughness map

    A roughness map determines how sharp or blurry reflections of the material are. It is a grayscale texture with perfect white representing parts that are completely matt, and perfect black parts that are sharp reflective. All the grayscale values between black and white give a reflection that is in-between sharp and blurry.

    The leather material has blurrier reflections in the folds and sharper reflections on the patches between the folds. That is why the folds are whiter in the texture.

    Applying the roughness map to a standard shiny gray material gives the following result:

    Normal map

    A Normal map does more or less the same as a bump map. They fake surface detail such as bumps, grooves, and scratches without having to model the actual surface details. Either a Bump or a Normal map is normally used. With a (personal) preference towards the normal map. As these tend to give better results.

    Normal maps most often have a purplish base color. In the Normal map the direction of the relief of the objects surface is captured in an RGB (Red, Green and Blue) color scheme. Each color represents a different axis of direction. The render software can interpret the different RGB hues and can then fake relief by adding shadows and highlights. You can clearly see the relief of the leather captured in the texture:

    Color map

    The Color map contains nothing more than all the colors of a material. We applied the Color texture before in this article. But now we will apply it with the Roughness and the Normal maps also applied to the material. You will see that this now gives a major difference:

    And compared to what we had before in the beginning of the article:

    Displacement map

    A Displacement map is something you can consider a really heavy weapon. As Bump and Normal maps fake surface relief, a Displacement map is used to actually create the surface geometry during rendering. 3D software have displacement techniques that basically break down your polygon object(s) into many, many, many really small triangular polygons (often far into the millions of polygons). And the Displacement texture is than used to actually displace your object’s surface.

    A Displacement map is a grayscale texture and the render software interprets the black color in the texture as the base surface height. Everything gray up to white is interpreted as being added relief on top of the surface:

    You can imagine that for the leather material the displacement is a subtle addition. But for the next example of a rock material, it means a difference between night and day:

    Click here, If you would like to see another example on texture build-up. This additional example is for a concrete road material that uses a bump, and glossiness map.

    3. Binoculars texture example

    We can use the same texturing techniques for the binoculars example. We will use textures to create changes in the material properties for amongst others the floor, the body and the side grips.
    The leather material covered before is actually the same material that is used for the grips on the body. But in this case the color is made more black.

    The huge difference that adding textures creates, can be seen in the comparison below.

    4. Labels

    In addition to the general textures used to mimic materials, there are many other applications on how textures can be used to add detail. I will not go into further details here, but only as an additional example I want to address the technique of labels. For example, with labels you can project logos on a model. This is also done in the final render for the binoculars. Below you can see that the brand logo is placed on the side of the binoculars as a label.

    Note!: There is one last side note I want to make. In the world of 3D there are a lot more types of textures and more importantly different types of workflows on how to use textures. Artists you might work with can have other types of software and therefore other workflows with textures.

    I hope you have enjoyed this post and have learned something new. Let me know if you have any questions or comments below.

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