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This one-sided area light emits a disk shaped illumination. The disk scale is adjusted by its scale transform which can be non-uniform.

An environment light source that implements a simple analytical physical model for terrestial daylight under clear skies. The sky model is based on A Practical Analytic Model for Daylight by A.J. Preetham, Peter Shirley, and Brian Smits. The solar disk model is adapted from H.C. Hottel's A Simple Model for Estimating the Transmittance of Direct Solar Radiation Through Clear Atmospheres, with parameters curve fitted for turbidity from physical data and a simple limb darkening model.



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


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


sunDirection: The apparent direction towards the center of the sun. The zenith is at +Z (for noon light) and the horizon is in the XY plane (for sunrise/set). Note that the Z component must non-negative. Ignored if a month is given.

RIB: vector sunDirection
Default: 0 0 1.0


The turbidity of the sky. The lower limit of the model is 1.7 for an exceptionally clear sky, and 10, for an inversion, is the upper limit.

RIB: float haziness
Default: 2.0

Sky Tint

Tweak the sky's contribution and color. The default, white, gives results based on measured physical values.

RIB: color skyTint
Default1.0 1.0 1.0

Sun Tint

Tweak the sun's contribution and color. The default, white, gives results based on measured physical values.

RIB: color sunTint
Default1.0 1.0 1.0

Sun Size

Scale the apparent size of the sun in the sky. Leave at 1 for a realistic sun size with an 0.55 degree angular diameter.

RIB: float sunSize
Default: 1.0


Month of the year, 1 through 12. The default, 0, means to use the explicitly given sun direction instead of automatically computing it.

RIB: float month
Default: 0


Day of the month, 1 through 31.

RIB: float day
Default: 1


Four digit year.

RIB: float year
Default: 2015


Hours since midnight, local standard time. May be fractional to include minutes and seconds. If daylight saving time is in effect, subtract 1 to correct to standard time.

RIB: float hour
Default: 14.633333


Standard time zone offset from GMT/UTC in hours. Positive for east, negative for west. For example, this would be -8 for Pacific time.

RIB: float zone
Default: -8


Latitude in degrees. Positive for north, negative for south. Ranges from -90 to +90 degrees.

RIB: float latitude
Default: 47.601903


Longitude in degrees. Positive for east, negative for west. Ranges from -180 to 180 degrees.

RIB: float longitude
Default: -122.331817


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


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
Default0.0 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: ""


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: ""


RenderMan for Maya includes useful presets for specific times of day.