Illumination
Every scene has a light source. The position of the light source in a scene affects which parts of
the surface are illuminated and which are shaded. The position is
defined by an azimuth and an altitude setting.
Azimuth is a compass direction,
measured clockwise in degrees from 0 (due north) to 360 (also due north). The
default azimuth is 315 degrees, placing the light source in the northwest.
Altitude is the angle, measured in
degrees from 0 to 90, between the light source and the horizon. An altitude of
0 degrees means the light source is level with the horizon; an altitude of 90
degrees means it is directly overhead. The default is 30 degrees.
With the sun in the northwest at 30 degrees above the horizon, the gray
block is illuminated as shown (when viewed from the south).