Goraud Versus Phong Shading

We now understand that Goraud shading performs the calculations inside the vertex shader and leverages the built-in rendering pipeline's interpolation. Phong shading, on the other hand, performs all of the calculations inside the fragment shader – that is, per fragment (or pixel). With these two details in mind, can you guess some of the advantages and disadvantages of these two shading techniques?

Goraud shading is considered to be faster since the performed calculations are computed per vertex, whereas Phong shading is calculated per fragment. The speed in performance does come at the cost of accurate or more realistic interpolation. This is most noticeable in cases where a light's intensity does not linearly degrade between two vertices. Later in this chapter, we will cover these two techniques in more detail.