8

Sunlight and Daylight Systems 395
•Daylightcombines sunlight (page 3–1112)
and skylight (page 3–1106) .Thesunlight
component can be either an
IES Sun light (page
2–1163)
,orastandardlight(a target direct
light (page 2–1145)
). The sk y component can
be either an
IES Sky light (page 2–1165) or a
Skylight (page 2–1149) .
TheIESSunandIESSkylightsarephotometric
lights. It is appropriate to use them if you are
creat ing a rendering that uses
radiosity (page
3–50)
with exposure control (page 3–289) .
TheStandardlightandSkylightarenot
photometric. It is appropriate to use them if
your scene uses standard lighting (Sunlight
with its Directional light works for this, too), or
if you are using
light tracing (page 3–43) .
Large view shows compass and light in a viewport. The
resulting rendered images are seen above it.
Note: When you create a sunlight system or a
daylight system that uses a target direct light for
the sun, the directional light’s hotspot is set to
encompass all geometry in the scene, so that
shadows will render correctly. Specifically, the
diameter of the hotspot is set to 65 per cent of the
longest diagonal length of the
scene extents (page
3–1101)
.
Procedures
To create a sunlight or daylight sy stem:
1.
On the C reate panel, click Systems
and then click Sunlight or Daylight.
2. Choose a viewport in which to create a compass
rose (the compass direction of your "world").
This should be a Top or P erspective view.
3. Drag to create the radius of a compass rose (the
radius is for display purposes only), and then
click and move to set the
orbital scale of the sun
light over t he compass rose. This can be any
distance you find convenient, since directional
and IES Sun lights produce parallel illumination
regardless of where their icon is located.
Upon creation you have two objects in your
scene:
•The
compass rose (page 2–26) ,whichis
ahelperobjectthatprovidestheworld
direction for your sun.
• The light itself, which is a child of the
compass rose, and is permanently targeted
on the center of the compass rose.
If you created a Daylight system, the Daylight
Parameters rollout on the Modify panel lets
you choose t he t ype of sunlight and skylight.
The Sunlight drop-down list lets you choose
between Standard (directional) or IES Sun.
The Skylight drop-down list lets you choose
between Skylight or IES Sky. Both these lists
offer you the option of choosing no sunlight
or no skylight.
Controls for the geographic location and time
of day are on the Motion panel. The default
timeisnoon,andthedefaultdateandtimezone
are based on your computer’s local settings.
The default location is San Francisco, CA.
The directional light created by the system is
managed by two special controllers: Solar Dat e
and Solar Time. After you create your system,