## CS 455 Lecture 6 – Matrices

### Agenda

- what ?s
- dot product
- recasting rotation, scaling
- homogeneous coordinate
- recasting translation
- a Matrix4 class

### TODO

- Read about calculating normals and shading. I encourage you to read a few other sources as well. Bring a 1/4 sheet with 3-4 questions or observations. You are welcome to answer any these challenge questions:
- If a light is infinitely far away, what can you say about how it hits different points of a surface?
- What happens when a red light illuminates a green surface?
- How is it that we can use the dot product to get the cosine of the angle between the normal and light vectors?
- How would you calculate a fragment’s “litness” given multiple light sources?
- Does a diffuse surface’s appearance change as the viewer moves around a scene? Why or why not?

### Code

…

### Haiku

**guns hurt people, and so do matrices**

Matrix to the face

My nose twists, shifts, and swells

Like two 2x4s