Table OF Contents
- Common Light Parameters
Introduction
IES stands for Illuminating Engineering Society. The IES data format describes the distribution of light from a point source. Most major manufacturers of lights provide IES profiles which can be downloaded for free.
Redshift IES lights use IES profiles to define the light's intensity and distribution.
Below are some examples of different IES light profiles, note their drastically different light distribution patterns.
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Redshift automatically creates a simple geometric shape in the viewport that roughly illustrates the IES light's distribution pattern.
Below you can see the viewport of the same scene, note how the viewport shapes below mimic the light cast in the example above.
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Parameters
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General
On
Turns the light on or off.
Intensity
Intensity Multiplier
Specifies a multiplier for the light intensities described in the IES profile. This parameter allows you to scale the IES intensity up or down.
Exposure
Specifies an f-stop value to intuitively match the light's intensity to a plate or rendering scenes without using extremely large or small Intensity values. A value of 0.0 means the exposure parameter does not alter the lights intensity.
For example, an Exposure value of 1.0 means the light doubles in intensity and a value by 2.0 means the light quadruples in intensity, etc.
Color
Mode
Specifies the color mode.
- Color: Light color is specified by the Color parameter below.
- Temperature: Light color is specified by the Temperature parameter below.
Specifies the color of the light using (R,G,B) values when mode is set to Color.
Temperature
Specifies the color of the light using a color temperature value (in Kelvin) when mode is set to Temperature. Redshift supports color temperatures between 1667K and 25000K. Lower values are 'warmer' or more red, while higher values are 'cooler' or more blue.
IES Profile
Specifies the IES file to use for the light.
Common Light Parameters
Shadow
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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.
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| 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.
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| 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
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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
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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.
- Never - Specular rays do not bend. This is the legacy lighting behavior.
- Auto - Specular rays bend through refractions if they are not too rough and bias towards not bending if they are rough.
- Always - Specular rays bend through refractions regardless of ray roughness.
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.
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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.
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| 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
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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:
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Diffuse: A green Standard material with reflections.
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Reflection: A fully metallic Standard material with diamond plate bump mapping and no diffuse component.
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Transmission: A fully transmissive Standard material with reflections.
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Single Scattering: A pink transmissive Standard material with single scattering and reflections.
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Multiple Scattering: A teal sub surface scattering Standard material with reflections and a very subtle diffuse component.
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Volume: A blue Standard Volume material with no emission.
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Global Illumination: The Cornell box demonstrates bounce lighting in shadow regions where no direct lighting is cast.
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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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| Toon Rim: 0 - 2 Other Contribution Types: 1 |
1 0 (Isolated for Reference) |
Caustics
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Casts Caustics
By default, all Redshift lights start in a Casts Caustics mode called "Render Settings". In this mode, a light's caustic capabilities are controlled by the "Light Casts Caustics" parameter found in the Caustics tab of the Render Settings. This allows you to easily control all lights in a scene from the Render Settings, making caustics much more simple to set up and control.
When Casts Caustics is set to "Render Settings" the default behavior of lights is:
- The light cast caustics
- Override Refraction Shadows is enabled
When Casts Caustics is set to "On":
- The light casts caustics
- Override Refraction Shadows is enabled by default but can be manually disabled.
When Casts Caustics is set to "Off":
- The light does not cast caustics
- Override Refraction Shadows is disabled
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| Casts Caustics: On | Off |
Override Refraction Shadows
Only editable when Casts Caustic is set to "On."
Casts Refraction Caustics must be enabled on an object for this option to have any effect.
When enabled, Transmission Shadow Opacity is set to 1 for Standard Materials that are lit by any light with this option enabled. This ensures that a transmissive object's shadow is appropriately dark so that it can be lit up by the more realistic caustics.
Intensity
Controls the brightness of the caustics as a multiplier relative to the intensity of the light. For the most realistic look use a value of 1 for caustics that match the intensity of the light. Increasing this value results in brighter caustics. A value of 0 can be used to effectively disable caustics for the light but Override Refraction Shadows will remain in effect, resulting in opaque shadows for transmissive materials.
Photon Multiplier
Controls the number of photons cast for the light. This is determined by multiplying the Photon Multiplier value by the "Num Photons" value found in the Photon Caustics Render Settings.
For example, if Num Photons is 10,000 and the Photon Multiplier is set to 1.5 then the light will cast 15,000 photons. If the Photon Multiplier were set to 3 then it would cast 30,000 photons.