Shading methods and light reflection models

The terms shading and lighting are commonly interchanged ambiguously. However, they refer to two different concepts: on one hand, shading refers to the type of interpolation that is performed to obtain the final color for every fragment in the scene. We will explain this in a moment. Let's say here as well that the type of shading defines where the final color is calculated—in the vertex shader or in the fragment shader; on the other hand, once the shading model is established, the lighting model determines how the normals, materials, and lights are combined to produce the final color. The equations for lighting models use the physical principles of light reflection. Therefore, lighting models are also referred to in literature as reflection models.

Shading/interpolation methods

In this section, we will analyze two basic types of interpolation method: Goraud and Phong shading.

Goraud interpolation

The Goraud interpolation method calculates the final...