9.5.2

372 • CHAPTER 7
OBJECTS MENU • LIGHTING • 373
Sun Light
The sun light source is a special case of a light. It is a light source with its Type set to Distant and
Shadow set to Hard (you’ll nd both these parameters on the General page of the Attribute manager).
Additionally, the sun light source has an expression tag that allows you to dene the exact time of day,
date and geographical position for the sun. The sun is of particular interest to architects who often
want a scene illuminated with a light that has the correct direction and color of the sun.
South is in the direction of negative Z-axis of the world coordinate system; the sun will always be here
at 12 noon. East (sunrise) is therefore in the direction of positive X-axis, west in the direction of the
negative X-axis, and north in the direction of the positive Z-axis.
The sun light source is placed far away from the origin of the world coordinate system. Owing to its
distant position, it radiates parallel light. The sun shines only if it is above the horizon (day). To animate
the sun you should therefore disable the Auto Light option in the render settings (Options page).
Otherwise, the scene will be illuminated by the auto light after sunset.
The color of the sun depends on the absorption spectrum of the mantle of air around the Earth and is
normally yellowish during the day, shifting into the red spectral region as the sun nears the horizon.
The sun light is intended for users who want to simulate realistic colors and shades at different times
of day, appropriate for landscape planning or house building.