Light and Shade

Lighting with dot products

An interactive lesson with 8 steps, about 7 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Lambert: matte brightness = max(0, n · l) = cos of the angle to the light.
• Phong highlights: (r · v)^s, where r = 2(n · l)n − l.
• Higher shininess s gives smaller, sharper highlights.

Steps

1. The cosine law
2. Lighting a sphere
3. A dot product
4. Half brightness
5. Shiny highlights
6. Ray tracing
7. The reflected ray
8. Just off the highlight