Although the terms shading and lighting are often ambiguously interchanged, they refer to two different concepts.
Shading refers to the type of interpolation that is performed to obtain the final color for every fragment in the scene. Later, we will explain how the type of shading determines where the final color is calculated – in the vertex shader or in the fragment shader.
Once the shading model is established, the lighting model determines how the normals, materials, and lights need to be combined to produce the final color. Since the equations for lighting models use the physical principles of light reflection, lighting models are also referred to as reflection models.
