# Lighting

There are just a few significant variables in the basic lighting equation:

1. The unit vector $\V{n}$ normal to the surface.
2. The unit vector $\V{l}$ toward the light.
3. The unit vector $\V{v}$ toward the viewer.
4. The color of the object $\V{c}_o$.
5. The color of the light source $\V{c}_l$.

The “half-angle” vector $\V{h}$ is half-way between the light vector $\V{l}$ and the view vector $\V{v}$.