In Chapter 2, Creating Your First Level, we selected a walnut polished material and applied it to the ground. This changed the simple dull ground into a brown polished wood floor. Using materials, we are able to change the look and feel of the objects.
The reason for a short introduction of materials here is because it is a concept that we need to have learned about before we can construct a Static Mesh. We already know that we need Static Meshes in the game and we cannot only rely on the limited selection that we have in the default map package. We will need to know how to create our own Static Meshes, and we rely heavily on Materials to give the Static Meshes their look and feel.
So, when do we apply Materials while creating our custom Static Mesh? Materials are applied to the Static Mesh during its creation process outside the editor, which we will cover in a later section of this chapter. For now, let us first learn how Materials are constructed in the editor.
To fully understand the concept of a Material, we need to break it down into its fundamental components. How a surface looks is determined by many factors, including color, presence of print/pattern/designs, reflectivity, transparency, and many more. These factors combine together to give the surface its unique look.
In Unreal Engine, we are able to create our very own material by using the Material Editor. Based on the explanation given earlier, a Material is determined by many factors and all these factors combine together to give the Material its own look and feel.
Unreal Engine offers a base Material node that has a list of customizable factors, which we can use to design our Material. By using different values to different factors, we can come up with our very own Material. Let us take a look at what is behind the scene in a material that we have used in Chapter 2, Creating Your First Level.
Go to Content Browser | Content | Starter Content | Materials and double-click on M_Brick_Clay_New. This opens up the Material Editor. The following screenshot shows the zoomed-in version of the base Material node for the brick clay material. You might notice that Base Color, Roughness, Normal, and Ambient Occlusion have inputs to the base M_Brick_Clay_New material node. These inputs make the brick wall look like a brick wall.
The inputs to these nodes can take on values from various sources. Take Base Color for example, we can define the color using RGB values or we can take the color from the texture input. Textures are images in formats, such as .bmp, .jpg, .png, and so on, which we can create using tools, such as Photoshop or ZBrush.
We will talk more about the construction of the materials a little later in this book. For now, let us just keep in mind that materials are applied to the surfaces and textures are what we can use in combination, to give the materials its overall visual look.
Notice that I have used both Materials and Textures in the previous section. It has often caused quite a bit of confusion for a newbie in the game development. Material is what we apply to surfaces and they are made up of a combination of different textures. Materials take on the properties from the textures depending on what was specified, including color, transparency, and so on.
As explained earlier, Textures are simple images in formats such as .tga, .bmp, .jpg, .png, and so on.
Now, we understand that a custom material is made up of a combination of textures and material is applied onto surfaces to give the polygon meshes its identity and realism. The next question is how do we apply these numerous textures that come with the material onto the surfaces? Do we simply slap them onto the 3D object? There must be a predictable manner in which we paint these textures onto the surfaces. The method used is called Texture Mapping , which was pioneered by Edwin Catmull in 1974.
Texture mapping assigns pixels from a texture image to a point on the surface of the polygon. The texture image is called a UV texture map. The reason we are using UV as an alternative to the XY coordinates is because we are already using XY to describe the geometric space of the object. So the UV coordinates are the texture's XY coordinates, and it is solely used to determine how to paint a 3D surface.
We will first need to unwrap a mesh at its seams and lay it out flat in 2D. This 2D surface is then painted upon to create the texture. This painted texture (also known as Texture Map) will then be wrapped back around the mesh by assigning the UV coordinates of the texture on each face of the mesh. To help you better visualize, take a look at the following illustration:
Source: Wikipedia (https://en.wikipedia.org/wiki/UV_mapping)
As a result of this, shared vertices can have more than one set of UV coordinates assigned.
To create a better appearance in surfaces, we can use multiple textures to create the eventual end result desired. This layering technique allows for many different textures to be created using different combinations of textures. More importantly, it gives the artists better control of details and/or lighting on a surface.
Normal Maps are a type of texture maps. They give the surfaces little bumps and dents. Normal Maps add the details to the surfaces without increasing the number of polygons. One very effective use of Normal Mapping is to generate Normal Maps from a high polygon 3D model and use it to texture the lower polygon model, which is also known as baking. We will discuss why we need the same 3D model with different number of polygons in the next section.
Normal maps are commonly stored as regular RGB images where the RGB components correspond to the X, Y, and Z coordinates, respectively, of the surface normal. The following image shows an example of a normal map taken from http://www.bricksntiles.com/textures/:
