Graphics Reference
In-Depth Information
Light Radius
All traditional lights have the option for a Spread Angle or Radius (to soften shadows and lighting). With
these options enabled, two fields become active: Samples and Simple Shading. Samples controls the
overall quality of shadows by using more light rate calculations to smooth the effect of the softened light.
Simple Shading (on by default) calculates the light from a single point for Diffuse and Specular values.
Disabling Simple Shading causes Diffuse and Specular values to be calculated along with the shadows.
This results in higher quality and slower render time.
Directional Light
The default light type (
Directional Light
) essentially mimics the sun. This type of light does not originate
from anywhere inside 3D space but rather from a point infinitely far from the scene. As a result, the position
of this light is irrelevant, and the only parameter of light placement that needs to be considered is its direc-
tion (angle).
The Directional Light has control over Radiant Exitance (brightness), Shadow Type, and Spread Angle
(which controls the sharpness of shadows). These controls are typical to most lights. Because this type of
light does not originate from within the 3D space, there is no calculation of decay. This means that objects
closer to the light will not receive any difference in brightness than objects farther from the light.
One of the most powerful options for the Directional Light is the ability to turn it into a Physical Sun
light. When Physical Sun is enabled, a new set of controls decides the angle color and quality of light emit-
ted. By setting the time of day, the day of the year, and the physical location on Earth, this option can mimic
real daylight on Earth. By default, the negative Z direction is designated as North, but this direction can be
shifted by using the North Offset field.
Figure 4-1
shows an example of a Physical Sun model in a simple
scene.
Figure 4-1:
Physical Sun can mimic real daylight in a scene.
