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Dome Light

Table Of Contents


Introduction

The Redshift Dome Light is an infinite, texture-mapped area light. Using HDR images you can achieve high-quality lighting results that would otherwise require several lights. Since a single dome light can reproduce the lighting of several distant lights, it can help with performance too. Since an HDR image can originate from a real-world environment, the dome light is an important tool to match the lighting of cg elements with live-action elements. Ideally, High Dynamic Range (HDR) textures in OpenEXR format should be used because they can capture a wide range of intensities.

Redshift has a maximum limit of 4 dome lights per scene.

Dome lights cannot be combined with environment shaders. If the scene or any material uses environment shaders, the dome light will override them.

The intensity of color values in an HDR texture as well as the shape of high intensity areas have a direct impact on the intensity and shadow softness of the lighting in the scene. In a sense, a dome light's texture behaves like an area light: very small, very bright spots on a texture map will produce sharp shadows while large spots will produce softer shadows.

The small white squares create sharp shadows

The larger white squares create soft shadows

Global Illumination helps Redshift catch dome lighting more efficiently, particularly with indoor lighting situations. If you're getting dome light noise please try enabling GI before increasing dome light samples.

 


General

Dome Map

Specifies the image that will be used as a light source.

Below you can see the same scene lit with three different HDRI dome maps with "Enable Background" turned on.

Dome Map: Greenwich Park Circus Arena Skylit Garage
Example images use HDRI's from PolyHaven


Map Type

Specifies the type of image that is used as the light source:


Flip Horizontal

Some renderers use a different convention for how a dome light should wrap around the virtual world in the X axis. The 'flip horizontal' option, as the name suggests, flips the dome light in the X axis to help match the look of a different renderer.


sRGB

Enabling this setting applies an sRGB gamma curve to your dome map.


We recommend using HDR images for the dome light texture (which are inherently linear) but if you decide to use an 8-bit image (which are typically sRGB), please enable this option.


Gamma

This setting sets the gamma value for your dome map. Higher values can help increase contrast in the dome map while lower values reduce contrast. Depending on your dome map adjusting gamma can help to adjust your scenes lighting when you want sharper or softer shadows.

In the examples below the exposure has been adjusted slightly to counteract the gamma change. 

Gamma: 1.0
Exposure: 0.0

0.5
1.0

1.2
-1.0


Exposure

This setting increases or decreases the intensity of the light in "stops". Therefore, a value of one means "twice as bright", a value of two means "four times as bright" and so on. A value of -1 means "half as bright", a value of -2 means "quarter bright" and so on.

Exposure: 0

1

-1


Hue

This setting shifts the color hues of the dome map.

Hue: 0

60

180


Saturation

This setting sets the color saturation of the dome map. Values below 100 are desaturated and values above 100 are oversaturated.

Saturation: 100

30

170


Tint

This setting lets you apply a color tint to your dome map. The default of white results in an unaltered dome map.

The closer your tint color is to white the less affected your light color will be. For a mild color tint be sure to use a desaturated color, a fully saturated color can fully tint all the colors in the scene as pictured below in the saturated green example.

Tint Color:


Samples

Specifies the number of ray samples to use for the area light. More samples will produce smoother lighting and shadows. Generally, the larger and more intense an area light is, the more samples it needs to produce noise-free results.

In the examples below unified min and max samples have been set to 1 / 1 and global illumination has been disabled in order to better isolate the effect of the samples count for a dome light. 

 

Samples: 8

64

1024


 

Environment

Enable Background

When enabled this setting will render the dome light map as the background in your render. 

When enabled the dome light background will render with a solid alpha value of 1. If you need alpha for the background be certain to enable "Alpha Channel Replace" and set the alpha value appropriately.

Enable Background: Enabled

Disabled


Replace Alpha Channel

When enabled this allows you to override the texture's alpha values, this may be necessary if they are either non-existent or not correct.

Typically, for environment textures, the alpha value should always be 0.0, if you plan on compositing environment layers.


Alpha

This is the alpha value that will be used instead of the texture alpha values when "Alpha Channel Replace" is enabled.


Back-Plate

 

Enabled

When enabled you can render a custom back-plate texture as your scene background instead of the dome map.

Enable Background must be enabled in order to render with a back-plate.

In the examples below the grey floor object has been rendered as a matte object to better demonstrate the uses of a back-plate. In the first image the you can see only the dome map as the background however once the back-plate is enabled it completely replaces it. Note that you can still see the reflections of the dome map in the reflective ball, not reflections of the back-plate.

Back-Plate: Disabled

Enabled

Back-plate from Poly Haven


Map

The texture path for the back-plate.


sRGB

Enabling this setting applies an sRGB gamma curve to your back-plate.


Gamma

This sets the gamma value for your back-plate. 

Gamma: 1.0

0.5

1.2


Exposure

This setting increases or decreases the intensity of the light in "stops" for your back-plate. Therefore, a value of one means "twice as bright", a value of two means "four times as bright" and so on. A value of -1 means "half as bright", a value of -2 means "quarter bright" and so on.

Exposure: 0.0

1.0

-1.0


Hue

This setting shifts the color hues of the back-plate.

Hue: 0

60

180


Saturation

This setting sets the color saturation of the back-plate. Values below 100 are desaturated and values above 100 are oversaturated.

Saturation: 100

30

170


Aspect Ratio

This option allows you to set the aspect ratio of the back-plate texture.

In the example below you can see how in the render aspect ratio version all of the back-plate texture is squeezed into the frame horizontally.

Aspect Ration: Texture

Render
Back-plate from Poly Haven


Apply Camera Exposure Compensation

When enabled exposure compensation is applied to your back-plate.

Apply Camera Exposure Compensation: Enabled

Disabled


Common Light Parameters

Shadow

Enable

Enable or disable shadow casting.


Transparency

Specifies the transparency of the shadows cast by the light. Smaller values yield darker shadows. The default value of 0 will produce a completely black shadow. A value of 1 will produce no shadow at all.

The example below shows how a completely opaque sphere's shadow transparency can be controlled by this light setting.
Transparency 0 to 1


Softness

Specifies edge softness for non-area light shadows. A value of 0 means no softness and will yield sharp shadows. Values above 0 will produce softer shadow edges. 


Softness is not available for Physical lights when set to Area. The softness of an Area light is controlled by the light's size itself.


Softness 0 to higher values



Softness Affects Gobo

Enables soft gobo texture projection, to match the softness of the shadows, giving the same appearance as if the light was an area light.


Softness Affects Gobo is only available for non-Area Physical lights and IES lights.

 

Light Group

AOV Light Group

This is the name of the AOV light group this light is associated with.

For more information on Light Groups and how to set them up and use them please see here.

 

Contribution

Matte Shadow Illuminator

Specifies whether the light can illuminate 'Matte Shadow' surfaces (see Matte Shadow Catcher shader).


Matte Shadow Illuminator is only available for Redshift Physical and Redshift IES lights.


Affected by Refraction

This option allows you to control how specular reflections are affected by rough/refractive objects that block the light and whether or not the light rays bend as they pass through. Prior to 2.6.10 this option was not available and the light rays would never bend. Specular ray bending is an important effect for rendering realistic-looking glass and lenses.

This effect is available only for area lights and dome lights. Spot and IES lights can not be seen through bent rays because their source is infinitesimally small.

Care must be taken when using 'Always', as this can disable Multiple Importance Sampling, which is a crucial technique for getting clean renders for rough surfaces.

Light/Shadow linking is not available for specular rays that have been bent.


GI Max Trace Depth

This option lets you override the maximum trace depth for GI rays on a per-light basis.

 

Light Sampling Parameters

The following parameters are only visible and relevant when Automatic Sampling is disabled.

Light Samples

Specifies the number of ray samples to use for the light. Higher sample values will produce smoother lighting and shadows. Generally, the larger and more intense a light is, the more samples it needs to produce noise-free results.

Sampling values can range anywhere from smaller numbers like 32 to 4096 or higher all depending on your scene and lights. Values like 4096 or higher will not necessarily lead to the kind of slow-down you may be used to in other renders so don't hesitate to prioritize image quality and push this value until your scene looks smooth enough. For more information, see the Unified Sampling page.

 

Samples: 2 16 128

 

Volume Samples

Specifies the number of ray samples for the light to use for volume shading. Higher sample values will result in less volume noise.

 

Contribution Scale Parameters

 

The light contribution parameters covered below modify the scale of individual light shading elements. These parameters offer full creative control in adjusting how much a light impacts a scenes, they can even bet set above 1.

The example scene used below contains three of PolyHaven's marble bust model, the model on the left has a standard shader with diffuse, reflection, and multiple scattering components, the model on the right has a fully transmission shader with single scattering, and the model in the back has been turned into a volume object in order to demonstrate volume contribution. There are two area lights in the scene, a disc area light in the top center and a rectangular area light in the back right. Each light has a contribution value of 1 for each shading type but when a parameter is modified for the example images both lights are adjusted equally.

 

Diffuse Global Illumination Reflection

Transmission &
Single Scattering

 Multiple Scattering Volume
 
  Beauty


Diffuse

Scales the intensity a light has on diffuse shading.

Diffuse: 0 1 10
Observe in the first image that when there is no diffuse contribution there is also no global illumination bounce lighting.


Reflection

Scales the intensity a light has on specular reflections.

Reflection: 0 1 10

 

Transmission

Scales the intensity of a light when seen through a transmissive / refractive object.

A light must be visible in order for transmission scale to have any effect.

When a light is visible a transmission scale of 0 results in the same effect as disabling a light's visibility.

Transmission: 0 1 10

 

Single Scattering

Scales the intensity a light has on single scattering.

Single Scattering: 0 1 10


Multiple Scattering

Scales the intensity of the light when seen through sub-surface multiple scattered materials.

Multiple Scattering: 0 1 10


Global Illumination

Scales the intensity of a light's global illumination contribution.

Global Illumination: 0 1 10

 

Volume

Scales the intensity of a light's volume scatter contribution. A value of 0 disables volume scattering for the light.

Volume: 0 1 10
Observe in the first image the volume object in the middle is still illuminated by global illumination even though all lights have volume contribution set to 0.

 

Caustics

Caustic Photons

Enables caustic photon casting for the light.


Has no effect if Enable Caustics is not enabled in the Redshift Render Options under the Photon Mapping tab.


Intensity Multiplier

Specifies a multiplier for the caustic photon intensity, relative to the intensity of the light. A value of 1 will cause the emitted photons have the same intensity as the light. Smaller values will yield photons with relatively less intensity than the light, while larger values will yield photons with relatively more intensity.


Number of Photons to Emit

Specifies the number of caustic photons to shoot for the light.


 

Recumbent lion model from My Mini Factory and scanned by the  Thorvaldsens Museum.