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Table Of Contents


Global Illumination

The Global Illumination settings tab covers the use of indirect lighting in your scene.

For more information on the fundamentals and concept of GI please see these Global Illumation pages.


Enables or disables all global illumination.

Global Illumination: Disabled

Render Time (Min:Sec) : 2:59

Notes: Notice the dark shadow behind lantern due to no bounce lighting from global illumination.



Primary GI Engine

Sets the primary global illumination engine that will be used on the first indirect lighting bounce. The options available for Primary GI engine and their pros and cons are:

  • Brute Force (default)
    • Pros
      • Very accurate
      • No flickering in animations
      • Simple to control with one setting (Brute Force GI Rays)
      • Compatible with interactive feedback
    • Cons
      • Slowest GI engine
      • Can be very noisy with low Brute Force GI Rays

  • Irradiance Cache 
    • Pros
      • Can produce cleaner images much faster than Brute Force
      • GI result can be saved and loaded for each frame allowing for faster iteration when tweaking non GI settings
      • Handles large flat surfaces like building interiors very well 
      • Irradiance cache time tends to scale better than linearly when increasing image resolution
    • Cons
      • Can be splotchy and flicker in animations, frequently this is more distracting than standard visual noise.
      • More complex to control and fine tune for splotch and flicker-free results.
      • For scenes with lots of small detail (like foliage) irradiance cache tends to be less efficient than Brute Force
      • Not compatible with interactive feedback


Specifies the number of indirect lighting bounces that will occur.

If Bounces is set above 1 then the Secondary GI Engine will be used for all bounces 2 and up.

Introducing more GI bounces in your scene will often make your lighting brighter and more realistic but will also make the render time slower.

Sometimes increasing the number of bounces can result in lighting that looks "washed out," for this reason users sometimes choose to limit the number of bounces.

The scene shown below contains a few vertical tiles, one of which is lit with a strong spotlight. Note that these images were rendered using Irradiance Caching for the primary GI engine and Irradiance Point Cloud for the secondary GI engine.

Bounces: 1

Primary GI only. The right tiles are only lit by the direct lighting on the center illuminated tile.


Primary and Secondary GI. The indirect lighting on the right tiles is now bouncing off once and illuminating the left tiles. The ground below the right tiles now also receives extra illumination from this additional bounce.

Secondary Engine

Sets the secondary global illumination engine that will be used on all indirect lighting bounces after the first. The options available for Secondary GI engine and their pros and cons are:

  • Irradiance Point Cloud (default)
    • Pros
      • Helps make primary Brute-Force and Irradiance Cache faster and cleaner
      • Much more efficient for very difficult lighting situations
    • Cons
      • Requires some storage 
      • More options to manage than Brute Force
      • Only provides a benefit when multiple bounces are needed, if the scene contains lots of lights or when the lighting conditions are difficult

  • Brute Force (default)
    • Pros
      • Very accurate
      • No flickering in animations
      • Simple to control with one setting (Brute Force GI Rays)
      • Compatible with interactive feedback
    • Cons
      • Slowest GI engine
      • Can be very noisy with low Brute Force GI Rays

Only available when Bounces is set above 1.

Secondary Engine: Brute Force

Even with Brute Force GI 4000 rays, there is noise everywhere.

Irradiance Point Cloud

The results are much cleaner and the frame was completed in nearly half the time.

Conserve Reflection Energy

When enabled, Redshift uses a cheap trick which adds the reflection energy that would be lost (i.e. the reflection color tint) to the diffuse color tint of materials during GI calculation.

Redshift does not currently support reflection ray sampling during GI calculations which can lead to a loss of energy, so enabling "Conserve Reflection Energy" gives the illusion of reflection ray bounces contributing to GI, which can be particularly noticeable with strong or colored material reflections.


Brute Force GI


Controls the number of Brute Force GI rays to shoot per pixel. 

The higher the number the cleaner the result but the longer the render time.

Depending on the scene Brute Force GI can require extremely high numbers to adequately clean GI noise.

Rays: 16512

Irradiance Caching

Irradiance Cache data is a view-dependant GI method which means that it has to be re-generated when either the camera or any objects move. It also has to be regenerated if lights change (position or intensity) and if materials are adjusted. However, there are a few settings that do not affect the irradiance cache:

  • All antialiasing settings
  • Any parameter that has to do with "number of samples". For example "number of area light samples"

If you are making any last-minute adjustments to your frame and tweaking these kinds of parameters you can save some time by re-using the irradiance cache you computed last time using the "Load" mode.

Please refer to the Irradiance Cache page for more information.


Specifies the Irradiance Caching mode to be used from the following options:

  • Rebuild (don't save) - Redshift will compute a new irradiance cache from scratch (for each frame) but will not save it to disk. The frame will be rendered to completion.
  • Rebuild (prepass only) - Redshift will compute a new irradiance cache from scratch (for each frame) and will save it to the user-specified file. The final rendering pass will be skipped.
  • Rebuild - Redshift will compute a new irradiance cache from scratch (for each frame) and will save it to the user-specified file. The frame will be rendered to completion.
  • Load - Redshift skips the computation stage and the data is loaded from the user-specified file in the parameter below. The frame will be rendered to completion.


Specifies where to save or load the Irradiance Caching data depending on the Irradiance Caching mode as covered below.

  • Rebuild (prepass only) - Save Irradiance Caching data to the user-specified file.
  • Rebuild - Save Irradiance Caching data to the user-specified file.
  • Load - Load Irradiance Caching data from the user-specified file.

Flythrough Mode

When enabled, allows Redshift to compute the current frame's irradiance cache points while using the last frame's points.

This mode should only be used on flythrough animations, i.e. only when the camera is moving.

If any objects or lights move, this parameter will produce visual artifacts.

 Since this mode helps with construction of irradiance cache points, it's only available on the two "Rebuild" modes and is grayed out for "Load."

Frames to Blend

When enabled, allows Redshift to average the results of multiple irradiance cache files (one for each frame) together.

Only available when Irradiance Caching is set to Load mode since it relies on loading pre-existing irradiance cache data for multiple frames.

Irradiance Cache frame blending can be used to improve flickering that might be present due to insufficient quality settings and/or difficult lighting situations.

Please refer to the Irradiance Cache page for more information.

Show Calculation

When enabled, a rough estimate of the Irradiance Cache points is made visible in the render view to help visualize the results as they are computed.

It will almost certainly contain noise and some visual glitches – don't worry, though, these are to be expected!

Separate Points for Secondary Rays

When enabled, irradiance cache points are treated separately for secondary rays like reflection and refraction in an effort to reduce flickering.

By default, irradiance cache points generated by primary (camera) rays are stored together with points generated by secondary rays such as reflection and refraction. While this is typically ok, sometimes there can be flickering artifacts caused by this because the point densities can vary wildly. If you're getting flickering artifacts on scenes using reflections/refractions, this option will treat the points separately and try to avoid such issues. 

Treating the points separately incurs a (typically) small performance and storage cost, so enabling this option is advisable only if such flickering issues occur.

If you're getting irradiance cache flickering issues, we recommended rendering a few frames both with and without reflections/refractions. You can quickly enable/disable reflections/refractions in the Globals tab.

Please ensure that you enable the "Separate Points for Secondary Rays" option only if you are see flickering with reflections/refractions enabled and no flickering with reflection/refraction disabled!

Visualize Points

When enabled, Irradiance Cache points will be rendered as small discs with an added bit of color to each point to make sure that even near-black ones can be seen.

This diagnostics mode is useful in finding out if some settings are too aggressive. For example if you see a mostly flat part of the image containing too many points this might mean that "Color Threshold" is too aggressive.

Using this mode can also help users better understand the effect that thresholds can have on the point densities.


The Preset section allows you to quickly switch between pre-defined quality settings that adjust the Irradiance Cache settings covered below.

There are 4 Presets to choose from:

  • Custom (default) - User controlled mode with default quality settings that sit in between Low and Medium.
  • Low
  • Medium
  • High

Min Rate

Max Rate

Color Threshold

Distance Threshold

Normal Threshold

Min Detail

Radius Factor

Smoothing Passes

Irradiance Point Cloud



Frames to Blend

Screen Radius

Samples per Pixel

Filter Size

Retrace Threshold

Show Calculation