Area Light Intensity

Color

Defines the light color.

Intensity

Species the light intensity.

Exposure

This is an additional control over the standard light intensity. Exposure is in many cases a preferred control due to its likeness to photography. Final light intensity is thus computed by:

I = intensity * pow(2, exposure)

Light Spread

Specifies the spread of the light. A spread of 1 is to natural "cosine" spread. Lower spreads will produce a more focused light. From left to right: 0.2, 0.5 and 1.0 (default).

Decay Rate

Specify the rate at which the light intensity decreases in function of the distance to the light source. The available values are:

Parameter	Description
No Decay	Light intensity remains constant with respect to distance.
Linear	Light intensity decreases linearly with distance.
Quadratic	Light intensity decreases proportionally to the square of the distance. This is the physically correct behaviour.
Cubic	Light intensity decreases proportionally to the cube of the distance.

Normalize Intensity by Area

This will devide the total intensity of the area light by its area. The net effect of this is that no matter the scale of your area light, the intensity will remain the same. This non-physical behaviour can be handy when adjusting shadows from area light: shadow softness adjustments (area light size) will not change the overall intensity. From left to right: off (default) and on.