Most Redshift lights share the features covered below. Some parameters may be unavailable with certain light types, in such cases this is called out.
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.
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.
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 offers creative flexibility, each can be raised or lowered and even completely disabled.
For physically correct results all contribution values should be left at 1 so the contribution of each shading component is equal and it matches a light's overall intensity. A value of 1 is indicated by a blue pole at the center of the bar in the examples below, when the bar is to the left of the pole then the output is lower than physically accurate and when the bar is to the right the output is greater than physically accurate.
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. The components and materials used in the scene are:
Camera: An additional light used to demonstrate camera visibility and transmissive effects where relevant.
Diffuse: A green Standard material with reflections.
Reflection: A fully metallic Standard material with diamond plate bump mapping and no diffuse component.
Transmission: A fully transmissive Standard material with reflections.
Single Scattering: A pink transmissive Standard material with single scattering and reflections.
Multiple Scattering: A teal sub surface scattering Standard material with reflections and a very subtle diffuse component.
Volume: A blue Standard Volume material with no emission.
Global Illumination: The Cornell box demonstrates bounce lighting in shadow regions where no direct lighting is cast.
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
Camera
Only available for area lights and dome lights.
Scales the visibility of the light to camera rays. Lower values dim the visible appearance of the light to the camera while higher values make the light appear brighter. A value of 0 makes the light appear invisible to the camera.
Note that this does not affect the contribution of a light on any materials or objects in the scene, it only affects the direct visibility to the camera.
Scales the intensity of light for diffuse shading. Diffuse shading is generally responsible for the base color shading of most materials.
Note that this affects global illumination intensity as well.
Diffuse: 0 - 2 Other Contribution Types: 1
1 0 (Isolated for Reference with GI disabled)
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 intensity of a light as seen through a transmissive / refractive material. This can be thought of as the visibility of a light in a transmissive material.
Note that a light can be visible in transmissive materials even when the Camera contribution is set to 0 — making the light appear invisible to the camera but still visible in transmissive materials. In this example the light has Block Rays enabled so the light casts shadows even when Camera is set to 0.
Transmission: 1 Camera: 0
1 1
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 infinite 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
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
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.
Legacy
Non-Area Light Intensity
This option is only relevant for Point, Spot and Infinite light types.
Non-Area Light Intensity activates a previous calculation method for these lights to preserve the look of older scenes. For new lights this option is disabled by default.
Soft Shadow Technique
This parameter is only relevant for Point, Spot, Infinite, IES and Physical Sun light types.
When enabled a previous calculation method for shadows will be used to preserve the look of older scenes. For new lights this option is disabled by default.
Project
In this tab, light link relationships can be made with objects in the scene.
Specifies whether the objects in the list should be excluding or included with respect to the light settings.
Objects
The list of objects that should be affected (in Include Mode) or not affected (in Exclude mode). For each object in the list the light behavior can modified to receive light, receive shadows, and to affect the object's children.
