2009

is 0.0 (a clear sky, blue in the daytime), but you can use the shader to change
the Haze value.
Interface
Diffuse Horizontal Illuminance The illuminance of the sky measured by a
luminance meter placed horizontally, outdoors, excluding the contribution
from the sun. Default=10000.0 lx.
You can animate this value.
Direct Normal Illuminance The illuminance of the sun measured by a
luminance meter aimed directly at the sun. Default=10000.0 lx.
You can animate this value.
NOTE If you have chosen American units as the active lighting units, the
illuminance values appear as footcandles (fc) rather than lux (lx).
CIE Sky Model
Create a Daylight system. > Choose mr Sky as the sky light. > Choose CIE as
the sky model. > mr Sky: CIE Parameters rollout
The CIE sky model is a physically accurate sky model recognized as an industry
standard. (CIE stands for Commission Internationale de l’Éclairage: the
International Lighting Commission.) It is controlled by two illuminance on
page 8009 values, and you can choose either an overcast or a clear sky.
When you render while the CIE sky model is active, the sky color derives from
the Haze value in the
mr Physical Sky shader on page 5181. By default this is
0.0 (a clear sky, blue in the daytime), but you can use the shader to change
the Haze value.
5180 | Chapter 18 Lights and Cameras