Chapter 4: UV Maps and Texture Baking

In the practical tutorials of Chapter 2, Having Fun with Modeling a Robot Drone Character, and Chapter 3, Let's Sculpt an Alien Plant!, you created a Robot Drone model and an Alien Plant model.

So far, these gray (untextured) models look great. Unfortunately, having these plain gray models on your virtual 3D movie set would not look that realistic, would it?

In order to make them look more real, first, we need to prepare the models so that they are able to receive textures and materials.

We will start by exploring some key concepts regarding textures and materials. Then, we will move on to learn about the concept of UV mapping.

After this, we will prepare our Alien Plants' shading and then go through the step-by-step process of UV mapping the model. We will do the same process for the Robot Drone model, but with some variations to our method since it is a mechanical model made up of multiple parts.

Once both Alien Plant...

Technical requirements

You will need the following hardware and software to complete this chapter:

• A computer that can run basic 3D animation software.
• You will need to install Blender from https://www.blender.org/download/.

The Blender version used in this chapter is version 2.93.5. Even if your version of Blender is newer, the examples should still work without any problems.

• You will need to install the latest version of xNormal from https://xNormal.net/.

The files related to this chapter are placed at https://github.com/PacktPublishing/Unreal-Engine-5-Character-Creation-Animation-and-Cinematics/tree/main/Chapter04

What are textures and materials?

In this section, we will explore the core concepts of textures and materials. First, let's start with the concept of textures.

Textures

In 3D computer graphics, we use something called a Texture (or a texture map) to describe an aspect of the mesh surface's appearance.

Usually, textures (or texture maps) are made from raster images (pixels in a grid format), or the textures can be procedurally generated (this is also known as Procedural Texturing).

Note

Procedural texturing is a 3D texturing method whereby textures and materials are generated by an algorithm inside 3D software (such as xNormal, Quixel Mixer, or Substance Painter). The algorithm uses information from your texture maps and/or 3D mesh, combined with settings that you have control over to create procedural textures. We will explain procedural texturing, in more detail, in Chapter 5, Texturing Your Models in Quixel Mixer.

Here is a brief description of the types...

Understanding UV maps

UV maps represent a 3D model's surface as a 2D representation, as shown in Figure 4.1.

Imagine a geographical map of the Earth; the map is 2D, but we all know that it is a flattened representation of the surface of our planet and that the map wraps around the spherical (globe) shape. Similarly, a 2D UV map represents a 3D surface.

You can download an example of an Earth Globe model (Earth.blend) at https://github.com/PacktPublishing/Unreal-Engine-5-Character-Creation-Animation-and-Cinematics/tree/main/Chapter04.

Open this Blender file and select the model named Earth. Then, click on the UV Editing Workspace tab to examine the UV map of this model.

This will give you a good understanding of the way that UV mapping works. See Figure 4.1 to view what this Earth model looks like in the 3D Viewport window and the UV Editor window:

Figure 4.1 – The Earth model and its UV map inside the UV Editor window (on the left-hand...

UV unwrapping the Alien Plant model

We will start our journey of learning about UV maps by UV unwrapping the Alien Plant model. Before we can start, we need to prepare the mesh's shading. In the next section, we will do just that.

Fixing shading issues

Import the Alien Plant model from the directory that you used when you completed the Using Instant Meshes for Auto-Retopology section of Chapter 3, Let's Sculpt an Alien Plant!.

Note

Low-poly describes a low-resolution mesh (that is, low geometric detail). Similarly, the term high-poly describes a high-resolution mesh (that is, dense geometric detail).

Open the low-poly Alien Plant model in Blender and switch to Edit Mode with Edge Selection mode turned on. You will notice that parts of the mesh's edges are displayed in a turquoise color. This is because we've imported the model as a .obj file from Instant Meshes, and some edges are set to display as sharp. Fortunately, there is a very easy way to fix...

UV unwrapping the Robot Drone model

In this section, you will UV unwrap each part of your Robot Drone model individually. Then, you will combine the unwrapped UV maps into a single UV map later.

We will start the lesson by loading the Robot Drone model that you created in the practical tutorial of Chapter 2, Modeling a Robot Drone Character. Perform the following steps:

1. Save a backup copy of the Robot Drone model that you created.
2. Delete the right-hand side of your Robot Drone's mesh parts, except for the body, as shown in Figure 4.9.
3. Separate all the parts of the low-poly model into individual objects. To do this, select all the faces of mesh parts that you have joined before. Press P to separate the model parts and choose the By Loose parts. Each new separated object part will also be listed in the outliner panel.
4. Use the Hide, Unhide, and Hide Unselected shortcuts to isolate model parts while you set your UV seams. By isolating model parts while setting...

Understanding texture baking

Texture baking is a process by which the xNormal software (I will cover xNormal in the Introduction to xNormal section) takes certain aspects from the surface of the high-poly model and then projects those aspects onto the surface of the low-poly model, to create new texture maps. These new texture maps can be used in procedural texturing software, such as Quixel Mixer.

Note

We will cover the use of Quixel Mixer in Chapter 5, Texturing Your Models inside Quixel Mixer.

The end result of the texture baking process is a texture map that holds information about various aspects of the high-poly model. For example, some of these aspects include the degree of sharpness of the edges of the model or information about fine geometric details on the high-poly model.

In xNormal, we can choose which aspects from the high-poly model we want to bake into a texture map. For our tutorial, we will bake three of these texture maps. The three texture maps that...

Introduction to xNormal

xNormal is a free, standalone 3D software that is very popular for baking texture maps.

The reason we're baking texture maps in xNormal is that the process of baking curvature maps in Blender is far too complex for the scope of this book, whereas xNormal is extremely quick and easy to use.

You now know what xNormal is used for. In the next section, we will learn how to prepare the Robot Drone model for use in xNormal.

Preparing the Robot Drone model for xNormal

Now, we need to export the Robot Drone model's high-poly and low-poly meshes so that we can bake the textures in xNormal.

There are two versions of the model to be baked: the low-poly mesh and the high-poly mesh.

Let's start by preparing the Robot Drone model's low-poly mesh first.

Preparing the low-poly mesh

In the UV unwrapping the Robot Drone model section, you separated all of your model parts. In other words now, the model parts are not attached to other model parts anymore.

We will now start to prepare the Robot Drone model's Low-Poly mesh for xNormal:

1. Move all of the separated mesh parts away from each other so that there are small distances between them, as shown in Figure 4.12:

Figure 4.12 – The low-poly version of the Robot Drone's model parts are all moved away from each other and then triangulated

Note

The reason we're moving the mesh...

Baking texture maps

In the previous section, you prepared and exported the Robot Drone model's high-poly and low-poly versions for texture baking.

In this section, we will start on the texture baking process of the Robot Drone model. Then, afterward, you will use the same method for baking the Alien Plant model.

Open xNormal. You will see a floating window with various menus:

Figure 4.14 – xNormal's UI with the High definition meshes tab currently enabled

We only need a few steps of preparation before we are ready to bake our texture maps. See Figure 4.14 for xNormal's UI:

1. Make sure the High definition meshes tab has been selected.
2. Right-click anywhere inside the xNormal's window part, as shown in Figure 4.14.
3. In the menu that pops up, select Add meshes and select your high-poly model.
4. Click on the Low definition meshes tab.
5. Right-click anywhere inside the window part of xNormal.
6. In the menu that...

Summary

ln this chapter, you learned about textures and materials. You understand how to UV map 3D models that are either organic-shaped or mechanical-shaped in form.

You also gained knowledge about how to fix shading issues and triangulate and separate mesh components. Finally, you have learned how to bake texture maps in xNormal.

Going forward from here, in Chapter 5, Texturing Your Models inside Quixel Mixer, our learning journey will take us to the procedural texturing exercises, where we will texture both the Alien Plant and Robot Drone models.