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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 contribution parameters covered below control how much a light is able to affect each shading component. The ability to control the intensity of each component individually offers creative flexibility, each can be lowered or completely disabled and even driven higher with values greater than 1. For physically correct results all contribution values should be left at 1 so a light's overall intensity is distributed equally to all shading components.

The example scene in this section features a Cornell Box with a bust from Three D Scans that is separated into pieces with different materials to illustrate the impact a light has on each shading component. Those materials are:

  1. Diffuse: A green Standard material with reflections.

  2. Reflection: A fully metallic Standard material with diamond plate bump mapping and no diffuse component.

  3. Transmission: A fully transmissive Standard material with reflections.

  4. Single Scattering: A pink transmissive Standard material with single scattering and reflections.

  5. Multiple Scattering: A teal sub surface scattering Standard material with reflections and a very subtle diffuse component.

  6. Volume: A blue Standard Volume material with no emission.

  7. Global Illumination: The Cornell box demonstrates bounce lighting in shadow regions where no direct lighting is cast.

  8. Toon Diffuse, Toon Reflection, Toon Rim: A toon material with a green diffuse component and a sine wave pattern, a white reflection component with a half tone dot pattern, and a light blue rim component.

 

Contribution Sections

 

Diffuse

Scales the intensity of light for diffuse shading. Diffuse shading is generally responsible for the most common base color shading of most materials.

Note that this affects the global illumination intensity as well.

Diffuse: 0 - 2
Other Contribution Types: 1		 1
0
(Isolated for Reference)


Reflection

Scales the intensity of light for specular reflections, the direct reflections of a light source.

Note that reflections of other objects are still seen in reflective materials even with a reflection contribution value of 0. In the example below, the metallic material with diamond plating is mostly heavily affected because it has no other shading component besides reflection, however, the specular highlights on the diffuse material, transmissive material, single scattering material, and multiple subsurface scattering material are affected as well.

Reflection: 0 - 2
Other Contribution Types: 1		 1
0
(Isolated for Reference)

 

Transmission

Scales the direct refractive specular intensity of a light seen through a transmissive / refractive material. This could also be thought of as the direct visibility of a light in a transmissive material.

Transmission: 0 - 2
Other Contribution Types: 1		 1
0
(Isolated for Reference)

 

Keep in mind that this only affects the visibility of a light source in a transmissive material, other objects can still be seen in transmissive materials. If a light source is not directly seen through a transmissive material this contribution parameter may have little to no visible effect. To demonstrate this, in the first example below a blue light is placed directly behind the transmissive material so the effect can be seen. However, in the second example, the light source is not seen directly through the transmissive material but the diffuse, global illumination, and other contribution types still illuminate the scene which are seen through the transmissive material. To put it another way, disabling transmission contribution does not stop a material from appearing transmissive the way disabling diffuse contribution results in a black diffuse material.

Transmission: 0 - 2
Directly visible light		 0 - 2
Indirectly visible light

 

Single Scattering

Scales the intensity of light for single scattering. Single scattering simulates microscopic particulate suspended in a medium and is part of the Transmission controls of a Standard Material — this is similar to multiple subsurface scattering but is better suited to thinner volumes.

Single Scattering: 0 - 2
Other Contribution Types: 1		 1
0
(Isolated for Reference)


Multiple Scattering

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

Multiple Scattering: 0 - 2
Other Contribution Types: 1		 1
0
(Isolated for Reference)


Global Illumination

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

Global Illumination requires Diffuse contribution, this is because global illumination simulates the secondary bounces that only occur after the first bounce of light which is what diffuse contribution represents.

Global Illumination: 0 - 2
Diffuse: 1
Other Contribution Types: 1		 1
1
0
(Isolated for Reference)

 

Volume

Scales the intensity of a light's volume contribution, this affects the scattering component of a volume material and environmental fog. A value of 0 disables volume contribution.

In the example below, a blue volume is illuminated by the light and the scene is demoed with and without environment fog.

Volume: 0 - 2
Other Contribution Types: 1
Without Environment Fog		 1
0
(Isolated for Reference)		 0 - 2
1
With Environment Fog

 

 

Toon Diffuse

Scales the intensity of a light's Toon Diffuse contribution. A value of 0 disables the effect.

Toon Diffuse: 0 - 2
1		 1
0
(Isolated for Reference)

 

Toon Reflection

Scales the intensity of a light's Toon Reflection contribution. A value of 0 disables the effect.

Toon Reflection: 0 - 2
Other Contribution Types: 1		 1
0
(Isolated for Reference)

 

Toon Rim

Only available for point, spot, and directional lights.

Scales the intensity of a light's Toon Rim contribution. A value of 0 disables the effect.

Toon Rim: 0 - 2
Other Contribution Types: 1		 1
0
(Isolated for Reference)

 

 

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.