Basic

Intensity

Scales the contribution of this light linearly.

The light intensity is computed using physical units which are typically 100.000 times too intense for regular RGB rendering. We scale it internally by 1e-e5 to generate pleasing illumination levels.

RIB: float intensity

Default: 1.0

Exposure

Specifies the exposure of the area light as a power of 2. Increasing the exposure by 1 will double the energy emitted by the light source. A value of 0 produces an intensity of 1 at the source, -1 produces 0.5.

RIB: float exposure

Default: 0.0

Angle Extent

Opening angle of the light source in degrees (sun=0.53).

RIB: float angleExtent

Default: 0.53

Distance

Distance of the light.

RIB: float distance

Default: 10000.0

Color

The color of the emitted light. If a color map is specified, this tints the color map

RIB: color lightColor

Default: | 1.0 1.0 1.0 |

Enable Temperature

Turns color temperature on or off.

RIB: float enableTemperature

Default: 0

Color Temperature

Allow the user to choose the color temperature of the light in Kelvins.

Unlike the basic light color, this allows the user to easily pick plausible light colors based on standard temperature measurements.

This control will act like a filter (a tinted transparent surface) in front of your light. If your light is white, you will get the chosen color temperature. If your light is colored, the color temperature will make it cooler (over 6500K) or warmer (below 6500K).

NOTE: The effect will be less pronounced on fully saturated mono-chromatic lights.

Defaults to 6500K, which should be very close to white on most monitors (D65 illuminant used by sRGB and Rec 709).

RIB: float temperature

Default: 6500

Refine

Emission Focus

Off-axis cosine power exponent to shape the emission. This controls the spread of the light. Higher number will start focusing the light towards the center and thus narrowing the light spread.

RIB: float emissionFocus

Default: 0.0

Emission Focus Tint

Off-axis light color tint. This tints the emission in the falloff region starting from the off-angle direction of the light towards the center. By default, the tint color is black. In addition to tinting, value greater than white will also increase the intensity of the falloff region.

RIB: color emissionFocusTint

Default: 0.0 0.0 0.0

Specular Amount

Amount of specular light that is emitted.

RIB: float specular

Default: 1.0

Diffuse Amount

Amount of diffuse light that is emitted.

RIB: float diffuse

Default: 1.0

Shadows

Note: All shadow parameters will be ignored if the light's bidirectional is enabled.

Enable Shadows

Enable raytraced shadows.

RIB: int enableShadows

Default: 1

Shadow Color

The color of the shadows cast by emitted light.

RIB: color shadowColor

Default: 0.0 0.0 0.0

Shadow Distance

The maximum distance of the shadow starting from the position of the point being shaded. -1.0 is unset which will use the distance between the point being shaded and the point on the light.

RIB: float shadowDistance

Default: -1

Shadow Falloff

The distance from the light at which shadow falloff begins. -1.0 turns off shadow falloff.

RIB: float shadowFalloff

Default: -1

Shadow Falloff Gamma

The gamma of the shadow strength in the falloff zone.

RIB: float shadowFalloffGamma

Default: 1.0

Trace Subset

Set of geometry to consider for traced shadow intersection. If this is not specified, all geometry are considered for traced shadow intersection.

RIB: string shadowSubset

Default: ""

Don't Trace Subset

Set of geometry to ignore for traced shadow intersection. If this is not specified, no geometry is ignored for traced shadow intersection.

RIB: string shadowExcludeSubset

Default: ""

Advanced

Trace Light Paths

Enable light and photon tracing from this light. When this is on,

RIB: int traceLightPaths

Default: 0

Thin Shadow

Enable thin shadow and disable refraction caustics for this light. This parameter will ignored if Trace Light Paths is enabled.

RIB: int disableRefractionDirectLighting

Default: 1

Light Samples

Specifies an override of the number of light samples to be taken for this light source. If set to something other than zero, it will override the sampling performed by the integrator.

RIB: int fixedSampleCount

Default: 0

Light Group

Specify the light group name used for light group LPEs.

RIB: string lightGroup

Default: ""