Phong shading is actually kind of interpolation method for 3D graphics surface shading, it was developed by Bùi Tường Phong. Rather than Phong shading, I want to talk about Phong reflection model here.
As Phong reflection model says, we can split light into three separate parts: Ambient, Diffuse, and Specular, and in the reverse way, we can forge light by adding these three kinds of element on objects. This is how to forge some light:
A: Ambient color; D: Diffuse color;
S: Specular color; P: Specular power;
N: Surface normal; E: Direction toward eye;
R: Reflection to light.
If we know the position and direction of light sources, the direction of sight, material and normal of each point of objects, we can use phong shading method to forge a scene of objects with light on them.
Here are some examples of phong reflection model.
1. Ambient only
2. Diffuse only
3. Specular only
4. Ambient + Diffuse
5. Ambient + Specular
6. Diffuse + Specular
7. Diffuse + Ambient + Specular
9. Diffuse + Ambient + Specular + Mirror