Game Development Reference
In-Depth Information
Figure 4.12
Examples in nature of ambient light (a) and directional light (b).
Directional Light
A
directional light
is a light without a position but that is emitted from a specific
direction. Like ambient light, directional lights affect the entire scene. However,
because directional lights come from a specific direction, they illuminate one side
of objects while leaving the other side in darkness. An example of a directional
light is the sun on a sunny day. The direction of the light would be a vector from
the sun to the object, and the side facing the sun would be brighter.
Figure 4.12(b)
shows a directional light at Yellowstone National Park.
Games that use directional lights often only have one directional light for the level
as a whole, representing either the sun or the moon, but this isn't always a case.
A level that takes place inside a dark cave may not have any directional lights,
whereas a sports stadium at night might have multiple directional lights to repres-
ent the array of lights around the stadium.
