Directional Light
The directional light simulates an infinitely distant light source, like the sun, that emits parallel light rays in one direction. Since the light source has no actual origin, the light rays are cast with the constant intensity and with no light falloff.
The only essential characteristic for this type of light source is its direction. The position of the light source or placement of objects in the scene is irrelevant, and does not affect the direction of shadows. The directional light can be used for uniform daylight illumination of an entire scene, either interior or exterior.
The intensity of the directional light can be measured in Luminance or Radiance. For details on the intensity controls, see the Common Physical Light Properties section.
In addition to common light properties, there are custom properties applied to directional lights only. You can find them in the Shadows section of the RPRPhysicalLightShape tab.
Shadow Softness
The Softness parameter in the Shadows section controls the strength or density of directional light shadows, and supports values from 0 to 1. Smaller values yield sharper and darker shadows, while greater values produce lighter shadows with soft edges.
Shadow softness: 0 |
Shadow softness: 0.25 |
Shadow softness: 0.5 |