A. What do we use interpolation for? What quantities might we want to interpolate?

B. How is the interpolation calculated? Give me a high-level overview.

C. What is the role of the fragment shader? What inputs does it take, and what outputs does it produce?

D. Similarly, what is the role of the vertex shader?

E. In 180mainEngine.c, please speculate about how I did the background sky effect.