Chapter 6: Intro to Materials

In the tutorial I’ve used:

  1. Unreal Editor.
  2. Material Editor.

With Unreal Engine 3.0, you are given the power to create worlds of stunning visual beauty and clarity. Materials are the single most important aspect to the final look of your game. Need a character that is so visually detailed that you could count the pores on her face? You can’t do it without a material. Need realistic looking fire for a particle system? You’ll need a flame-like material. Want to create a complex interactive machine with number readouts, lighted buttons, knobs, and switches? You’ll have to have a material to do that, too. No matter if you’re making large-scale environments, interactive objects, playable characters, or just simple props to spice up your level, a material must be used to control the object’s final look.

The very simplest way to think of a material in terms of a game engine is as a paint that is applied to surfaces of objects in your level.

Many newcomers to game design can have a difficult time differentiating between materials and textures. Simply put, the difference is that a texture is merely an image, while a material is a culmination of a variety many different elements, including textures. It is easiest to think of a texture as being a component of a material. When you create materials you will use textures to provide color, transparency, glow, and a variety of other effects for your material.

Part of the confusion in knowing the difference between materials and textures is that in versions of UnrealEd prior to the release of Unreal Engine 3, textures or materials could be applied directly to surfaces. This is no longer true. Only materials may be applied to surfaces. Textures are attached to the final material, which is then applied to the given surface.

Wrapping a static mesh with texture is done through texture coordinates (UVs).

Starting at the bottom left corner, the texture being applied to the surface is mapped from 0 to 1 horizontally and from 0 to 1 vertically. These are the U and V coordinates respectively, sometimes referred to as ‘tangent space’. Each vertex of a surface has values that correspond to the U and V coordinates of the texture that is to be applied to the surface. The texture is then painted onto the surface according to those texture coordinates

Figure – Here you can see how the UVs of a polygonal object affect how the texture is applied across the object’s surface

Once you start really getting into creating your own materials, you’re going to come across the word ‘instructions’. In this case, instructions are commands that are passed to the computer to handle various aspects of the material’s behavior. In fact, even when you create a basic material for the first time, you will notice that the Material Editor’s Expression Window tells you that the material contains many instructions by default, most of which are used to simulate the lighting on the surface of your material.

For the most part, your materials are useless without some sort of light in place to allow you to see them. Also, when you really get down to the bare bones of it, materials are all about controlling how a given surface responds to light.

In general, a material is comprised of three primary components that must all work in unison to create the final result. These components are Material Nodes, Material Channels, and Material Expressions. The three components interact in the manner described in the following diagram.

A normal map is essentially a texture that describes differing elevations across a surface, as well as the angles of each part of the surface as the elevation changes.

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