Redshift Light Groups in Cinema 4D: Setup, Light Linking and EXR Output

Redshift light groups split a render into one layer per light, or per group of lights, so you can change the brightness and color of each light in Nuke, After Effects or Fusion instead of re-rendering in Cinema 4D. This guide follows Maxon’s Redshift documentation: how to set light groups up, why the layers sometimes do not add up to the beauty, how light linking fits in, and which OpenEXR settings keep multi-light sequences manageable.

Checked against the Redshift documentation in the Cinema 4D help, November 2026.

A light group is a name you give to one or more Redshift lights. When a light-group-compatible AOV, such as Beauty or Diffuse Lighting, outputs light groups, Redshift writes a separate version of that AOV for each group. Adding the layers together in compositing rebuilds the image, and changing one layer changes only that light’s contribution (Maxon: Light Group AOVs).

Lights with the same AOV Light Group name share one layer, so you can group lights that do the same job, for example all rim lights. Not every AOV or effect can be split per light:

Sources: Maxon Redshift: Light Group AOVs.

Name your lights, add a Beauty AOV, choose the groups it outputs and set Global AOV to Remainder. The steps follow Maxon’s documentation for Cinema 4D.

Settings checklist (copy or follow line by line):

Redshift light › Attributes › Light Group
  AOV Light Group ....... key / fill_rim / dome  (same name = same group)

Render › Redshift AOV Manager
  Add AOV ............... Beauty
  Light groups .......... add to Light Group List, or enable All Light Groups
  Global AOV ............ Remainder  (writes "other" for ungrouped light)

Output .................. multilayer EXR, check each group in the RenderView

Step 1: Name each light

Select a Redshift light, open the Attributes Manager and type a name under Light Group > AOV Light Group, for example key, fill_rim or dome. Give lights that should stay together the same name.

Step 2: Add a light-group-compatible AOV

Open Render > Redshift AOV Manager and add the Beauty AOV. Beauty is the simplest choice for relighting: one layer per group. Add light groups to Diffuse Lighting, Specular Lighting or other AOVs only when the compositor needs to adjust those components per light.

Step 3: Choose the groups

In the AOV’s light group options, add groups to the Light Group List, or enable All Light Groups to output every group in the scene without listing them.

Step 4: Set Global AOV to Remainder

Remainder writes everything not covered by the selected groups to a layer with the suffix “other”. All writes the combined result instead. Only one mode can be used at a time, and Maxon describes Remainder as preferable in most cases.

Step 5: Check the layers before the batch render

Render a test frame and switch between the AOVs in the Redshift RenderView. Each group should show only its own lights, and “other” should be close to black when every light is grouped and every effect is ray-traced.

How fast the layer count grows (illustrative calculation): each light group is multiplied by each AOV that outputs it. Five groups on Beauty with Remainder give 6 layers (5 groups plus “other”). The same five groups on Beauty, Diffuse Lighting, Specular Lighting and GI give 24 layers. One 3840×2160 RGBA layer in 16-bit half float is about 66 MB before compression (3840 x 2160 x 4 channels x 2 bytes), so 24 layers are about 1.6 GB per frame uncompressed. Compression reduces this a lot, but the multiplication is the reason to output light groups only on the AOVs you need.

The figure shows what each layer looks like and how the layers add up.

Each layer holds only the light from its own group: the key layer shows the area light, the fill_rim layer only the edge light, the dome layer only the sky light, and “other” whatever cannot be split per light. Adding all of them in linear space gives the beauty, apart from small clamping differences, and changing one layer relights only that light.

Usually because of clamping, because some effects cannot be split per light, or because the “other” layer is missing from the composite. Maxon’s documentation describes each cause:

• Point-based effects: Irradiance Cache and Irradiance Point Cloud GI, point-based SSS and photon caustics cannot be assigned to a light group. They appear only in “other” (Remainder) or in the “All” layer. Switch to Brute Force GI and ray-traced SSS for clean groups.
• Ungrouped or unselected lights: they end up in “other”, so always include that layer.
• Clamping: the main beauty clamps the sum of all lighting, while each AOV clamps its own component, so the sum can differ. Maxon suggests raising the clamps, enabling AOV clamps (close but not exact), or clamping by luminance in compositing.
• Visible lights: a light that is visible to the camera is written to the Emission AOVs, not only to the lighting layers.

To rebuild the image, add the layers in linear space, for example with a Plus merge in Nuke or the Add blending mode in a 32-bpc linear After Effects project.

Sources: Maxon Redshift: Light Group AOVs, sections on limitations and clamping.

Light linking decides which objects a light illuminates; light groups decide which layer that light is written to. They work well together: a rim light linked only to the hero object and placed in its own group gives a rim layer that touches only the hero.

In Cinema 4D, open the Project tab of a Redshift light, set Mode to Include or Exclude, and drag objects into the Objects list. For each listed object you can toggle illumination, shadow casting and whether the setting applies to its children (Maxon: Redshift Light, Project). Include and Exclude can reach the same result, so use whichever list is shorter.

• Shadow linking is separate: you can keep a light illuminating an object but stop it casting that object’s shadow.
• GI still travels: in Maxon’s example, a linked light that ignores some objects still bounces onto them through global illumination, so a “linked” group layer is not always black outside the linked objects.
• Volumes: volume objects are not compatible with light linking.

The figure shows the part of light linking that is easy to miss: what actually ends up in the light group layer of a linked light.

The rim light is set to Include only the hero, so it gives no direct light to the floor or backdrop. Light that bounces off the hero is global illumination, so it can still reach those surfaces and is written to the same “rim” layer. If the compositor needs a layer with nothing outside the hero, use a mask or Cryptomatte in compositing rather than expecting light linking to produce pure black.

Sources: Maxon Redshift: Light and Shadow Linking, Redshift Light Project tab.

Write light group layers as 16-bit half float in a Multi-Part EXR, and choose compression by how the files will be used: lossless for exact data, DWAA or DWAB for much smaller files. In Cinema 4D these options are in the Redshift render settings, AOV tab, under Multi-Part EXR (Maxon: Redshift AOV tab).

If you save through Cinema 4D’s own Save settings instead of Redshift’s Multi-Part EXR output, Maxon support recommends setting the depth to 32 Bit/Channel and enabling Use 16 Bit Floats in the EXR options. Choosing 16 Bit/Channel there can write linear Rec. 709 instead of your OCIO render space (Maxon support).

Sources: Maxon Redshift: AOV Advanced, OpenEXR Technical Introduction, OpenEXR Standard Attributes, Maxon support: Color Management and EXR Output.

Both can render light group AOVs, because the setup is saved in the scene. A SaaS render farm, where you upload the scene and the farm renders it, suits finished scenes whose layers you have already checked and large batches you do not need to watch. An IaaS render farm such as iRender, where you work on a remote machine, suits scenes you still need to open in Cinema 4D, check layer by layer in the RenderView, or render with your own plugins and versions. In both cases, plan for the output size: with many groups and AOVs, download time can matter as much as render time.

These videos show Cinema 4D and Redshift projects rendered on iRender multi-GPU servers.

On iRender you rent a whole server with 2x, 4x or 8x RTX 5090 or RTX 4090 GPUs and a 2 TB NVMe drive, with Cinema 4D and Redshift pre-installed; Prime members get activated Cinema 4D and Redshift licenses. Render times and costs of real jobs are in our Redshift benchmark, and plans are on the Cinema 4D Redshift render farm page.

How do I create a light group in Redshift for Cinema 4D?
Select a Redshift light, open the Attributes Manager and type a name under Light Group > AOV Light Group. Lights with the same name share one group. Then open the Redshift AOV Manager, add a compatible AOV such as Beauty, and select the groups in its Light Group List or enable All Light Groups.

What is the “other” light group AOV in Redshift?
When Global AOV is set to Remainder, Redshift writes everything not covered by the selected light groups to a layer with the suffix “other”. It contains ungrouped or unselected lights and effects that cannot be split per light, such as point-based GI and photon caustics. Include it in the composite so the layers add up to the beauty.

Why does the sum of my light groups not match the beauty?
Usually because of clamping or point-based effects. The main beauty clamps the sum of all lighting, while each AOV is clamped on its own, so the sum can differ. Maxon suggests raising clamps, enabling AOV clamps, or clamping by luminance in compositing. Point-based effects only appear in “other” or “All”.

Do Redshift light groups work with Irradiance Cache GI?
Not per light. Light group AOVs are only compatible with ray-traced effects. With Irradiance Cache or Irradiance Point Cloud GI, the GI contribution goes to the “other” layer or the “All” layer instead of each light group. Use Brute Force GI if you need GI separated per light.

Should I use DWAA or DWAB for light group EXRs?
Both use the same lossy DCT compression from DreamWorks Animation. DWAB compresses 256 scanlines at a time and is more space-efficient and faster to decode full frames; DWAA compresses 32 scanlines and suits apps that read only part of an image. Keep utility AOVs lossless.

Does light linking work with volumes in Redshift?
No. Maxon’s documentation states that volume objects are not compatible with light linking. You can still use light groups for lights that illuminate volumes, because light groups and light linking are separate features.