UV-Unwrapping 3D Models for Texturing

In this chapter, we will learn how to UV-unwrap 3D models. This will give us more control over how textures are projected on a surface. We will begin by exploring what UV-unwrapping is and how it works, before learning how to do it correctly and practicing on some models.

We will learn about two methods of UV-unwrapping. First, we will learn how to unwrap objects manually, to give us full control over the result. Then, we will learn an easy method to automatically unwrap objects, which is quicker and easier but often looks less realistic.

By the end of this chapter, you will be ready to UV-unwrap complex 3D models both manually and automatically with Blender’s help. This will give us more control over the texture mapping process and allow us to bake custom textures and texture maps.

The following topics will be covered in this chapter:

• Understanding UV mapping
• Unwrapping basic shapes
• Unwrapping a cylinder
• Unwrapping...

Technical requirements

This chapter includes an exercise that will require you to download a Tiger Tank 3D model. The model can be found in the Chapter07 folder within the book's downloadable resources folder, available here: https://packt.link/mA1OU

Understanding UV mapping

UV mapping is the process of applying textures to 3D models by unwrapping them into two-dimensional maps known as UV maps. To understand how UV mapping works, we need to visualize a simple example. Figure 7.1 illustrates how a cube can be unwrapped into a 2D map.

Figure 7.1 – A UV-unwrapped cube

A cube will typically produce a UV map shaped like the surface shown in Figure 7.2. As you can see, some of the cube’s edges were cut to allow for unwrapping, but some of the edges stayed connected. We will learn which edges to cut shortly.

Figure 7.2 – The UV map of a cube

When placed over an image texture, the UV map covers a certain area, as shown in Figure 7.3. This covered area is then projected on the surface of the 3D object, as we saw previously in Figure 7.1.

Figure 7.3 – A UV map placed over a texture

Similarly, a cylinder can be UV-unwrapped...

Unwrapping basic shapes

We will now learn how to cut and UV-unwrap 3D shapes to create UV maps. In the following few steps, we will create and unwrap a basic cube. Although Blender typically automatically unwraps a default cube, it is important that we know how to do this manually since lots of 3D objects will need to be manually unwrapped like a cube, and Blender will not be able to do it automatically:

1. Open the UV Editing workspace from the top of the screen.

Figure 7.5 – Opening the UV Editing workspace

The screen is now split into two areas: the UV Editor on the left and the 3D View on the right, as shown in Figure 7.6. This allows us to see the 3D model and the UV map at the same time, as we are working. In Figure 7.6, we can see that the default cube, like all other shapes that can be added from the Add menu, is already unwrapped.

Figure 7.6 – A UV-unwrapped cube in the UV Editing workspace

...

Unwrapping a cylinder

We can use a similar technique when unwrapping a cylinder. Figure 7.12 shows which edges should be marked as seams on a cylinder to correctly UV-unwrap it.

Figure 7.12 – Marking seams on a cylinder

This will create a UV map, as shown in Figure 7.13.

Figure 7.13 – The UV map of a cylinder

As you can see, the UV map shows all the faces of the cylinder, unwrapped and displayed on a 2D surface. This allows us to place a texture onto this object, and the UV map will dictate how the texture is mapped on the surface.

We now know how to unwrap some simple shapes by marking their seams manually. Next, let’s look at how to correctly unwrap some more complex objects.

Unwrapping complex shapes

We will now use the simple unwrapping methods that we learned about to unwrap some more complex 3D models. For practice, we will unwrap the low-poly Tiger Tank turret, which can be downloaded using the link in the Technical requirements section of this book. You can see what it looks like in Figure 7.14.

Figure 7.14 – A Tiger Tank turret

This exercise will teach us all the most important principles necessary for UV-unwrapping, which will allow us to correctly UV-unwrap almost any other object:

1. First, let’s create a new image with an Image Texture node, in the material on the object, and set Generated Type to UV Grid.

Figure 7.15 – Generating an image

Applying the UV Grid texture to the object without any mapping will probably create a messy result, as shown in Figure 7.16. There is a lot of visible stretching, compression, and bending in the pattern, so the texture...

Summary

In this chapter, we introduced UV mapping as a means of applying textures to 3D models by manually or automatically unwrapping objects. We can use manual unwrapping when we need to ensure realism and are willing to invest extra time into unwrapping. We can use automatic unwrapping when realism isn’t very important, and we just need a quick UV map.

In the next chapter, we will use manual UV mapping to create Ambient Occlusion maps, which will allow us to increase the level of realism of our objects by making their shading more in tune with the environment.