Shading

Shading is roughly defined as the process of applying a lighting, or illumination, model to the surface of a polygon. Lighting and shading are vital to the 3D world, as they allow for realistic looking objects which can do cool things like reflect light (or look like they are reflecting light). A 3D game is not close to complete without good shading and lighting in it, so let us look at the different lighting and shading types.

Flat Shading

Flat shading, also called constant shading, is the simplest kind of shading, and is thus where we shall begin. Flat shading, simply put, fills the polygon's surface with one color. Typically, each facet, or face, of a polygon is given an illumination determined by an average value for the whole polygon.

Thus, each facet of a polygon is a single color, which does not allow for smooth shading. This is an example of the "Mach effect", occurs when you notice transitions in shading when it should actually be continuous. In the case of flast shading, we see that the light (or dark) intensity at the edges of the polygon faces are overestimated for light values and underestimated for dark values. Flat shading is not going to be acceptable for 3D gaming.

Flat shading