This is RenderMan 21 Documentation you are viewing. The Rmanwiki home page will redirect you to the current documentation.

Page tree

You are viewing an old version of this page. View the current version.

Compare with Current View Page History

« Previous Version 5 Next »

Contents

This infinite light simulates a bright distant light source like from the sun or moon. This light bathes the entire scene and treats the light as-if the rays are parallel by default (this can be altered in the settings below).

Only rotation (direction) will be applied. Translation and scaling of this light will be ignored.

You will see mention of "non-physical" controls. These controls are designed to help artists make art-directed imagery by ignoring certain laws of physics we usually simulate.

Parameters

 

Basic

 

Intensity

Scales the contribution of this light linearly.The light intensity is computed using physical units. The default light begins at a high value of 50000.000. Below we also have 10000 and 90000.




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. Real world lighting has high energies and typical exposures are low values while you may have to type a really large number for equivalent Intensity. This is also comfortable to artists familiar with photographic measurements. Below shows values -1.0, then 0.0, and finally 1.0.

 

 

Angle Extent

Opening angle of the light source in degrees (Sun=0.53). Higher values soften the shadow edges (light rays become less parallel) while lower values make it sharper. Below are the default of 0.53, 5.0, and then 10.0. Larger values increase shadow softness by increasing the angle of its light. Note that increasing this parameter also increases the amount of light in the scene and you may need to significantly reduce the light intensity/exposure to compensate.

 

 

Distance

Distance of the light.

 

Color

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

 

Enable Temperature

Turns color temperature on or off. Below we use the following temperatures: 6500K (default), 4000K, and lastly 8500K.

 

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 or gel (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).

 

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).

 

 


Refine

Emission Focus

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

 

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 (none). In addition to tinting, values greater than white will also increase the intensity of the falloff region.

 

Specular Amount

Amount of specular light that is emitted. This is a non-physical control.

 

Diffuse Amount

Amount of diffuse light that is emitted. This is a non-physical control.

 

 


Shadows

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

 

Enable Shadows

Enable raytraced shadows.

 

Shadow Color

The color of the shadows cast by emitted light. This is a non-physical control.

.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.

 

Shadow Falloff

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

 

Shadow Falloff Gamma

The gamma of the shadow strength in the falloff zone.

 

Trace Subset

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

 

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.

 

 


Advanced

 

Trace Light Paths

Enable light and photon tracing from this light.

 

Thin Shadow

Enable thin shadow (fake colored shadows for transparent objects) and disable refraction caustics for this light. This parameter will be ignored if Trace Light Paths is enabled.

 

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. You might find need for this if you have unsolvable noise from this light and need mroe samples.

 

Light Group

Specify the light group name used for light group LPEs. This is useful to generate per-light AOVs for later adjustment in compositing.