Introduction to shading

Shading is the process used to simulate the interaction of light with a material on a 3D object. With the presence of light, lighter and darker areas on an object can be calculated. Imagine a cube, made of one single color. When all sides use the same color, your object is barely recognizable as a cube, just like the following screenshot illustrates:

Because you were just told that it is supposed to be a cube, you can see that it is with some imagination. However, if you were to see this image outside the context of this book, chances are that you wouldn't have recognized it as a cube. Have a look at what happens when we apply a shader to the cube's materials:

That looks more like a cube, right? Depending on the angle between each side of the object and a light source, the color used on the side brightens or darkens. To achieve this you could define a different material color for each side of the cube. Depending on your situation, that might be good enough. However...