V-Ray Light Mix Guide: Adjusting Light and Color After Rendering

V-Ray Light Mix is a tool for adjusting the contribution of lights and emissive materials in a scene from the V-Ray Frame Buffer (VFB) after rendering. The workflows described in Chaos’ V-Ray for Blender and V-Ray for Cinema 4D documentation let you change light color and intensity, and toggle lights on or off. To use the feature, add the Light Mix channel or element to the scene before rendering. The documentation pages don’t specify a particular software version; the steps below cover the workflows documented for both applications.

What does Light Mix do?

Light Mix lets you change the lighting using controls in the VFB, without having to edit each light’s parameters individually. Adjustments can be made during or after rendering. You can compare different lighting looks, save settings as presets, and load them again later. This makes it possible to examine the contribution of individual lights in the same scene.

Blender documentation recommends setting lights to neutral white and increasing their intensity before rendering. If you render with low light intensity and then raise it in Light Mix, the image may develop noise. So Light Mix shouldn’t be treated as a way to render with insufficient lighting and fix every result afterward.

Setup: Blender and Cinema 4D

1. Add the Light Mix channel or element. In Blender, use View Layer Properties > Render Channels > Light Mix. The documentation also shows the path World Tree > Add > Render Channels > V-Ray Light Mix. In Cinema 4D, add the element via V-Ray > Render Elements > Add LightMix.

2. Check the lights before rendering. For Blender, Chaos recommends setting lights to neutral white and using high intensity. Since the documentation doesn’t give a specific numerical intensity value, don’t rely on a fixed figure; check the lighting settings for your scene.

3. Render the scene. The channel or element must be added before rendering for Light Mix to work. Then open the V-Ray Frame Buffer.

4. Select the Light Mix source in the VFB. In the Blender workflow, the source switches to Light Mix automatically when rendering starts. In Cinema 4D, set the Source field in the VFB’s Layers section to LightMix.

5. Adjust the lighting and save if needed. Enable or disable the relevant lights, then change the look using the intensity multiplier and color field. Use Save to save a preset and Load to load a previously saved setting.

Grouping lights and applying changes to the scene

The grouping option determines how light contributions are separated in Light Mix. Blender documentation describes options for individual lights, grouped lights, and manual selections based on Light Select elements in the scene. With grouped lights, any lights that aren’t assigned to a group remain in their own channels. With manual selection, lights not defined in Light Select elements are collected in the Rest channel.

The Cinema 4D documentation also lists instanced lights and layers as grouping options. In both applications, Light Mix can automatically create Environment and Self Illumination channels. To include emissive materials in the controls, use the Separate Emissive Material option. The documentation says this option covers V-Ray Material and V-Ray Light Material types that use non-black self-illumination.

In the VFB, Reset returns adjustments to their default values. To Scene applies Light Mix changes to the scene, but in Blender, items left in the Rest channel aren’t included. Both sets of documentation state that the option to apply changes to the scene is available after rendering has stopped. So if you need to transfer the final look to the scene’s light parameters, apply the changes separately after rendering is complete.

In Cinema 4D, pay attention to light names as well. Chaos documentation warns that saved Light Mix results may be overwritten if multiple lights have the same name. Check the names of lights in the scene and avoid duplicates to keep presets consistent.

Using Light Mix in architectural visualization workflows

Teams comparing different lighting options for interior, residential, or commercial visualizations can adjust lights from the VFB with Light Mix. For example, there’s no need to return to a light’s parameters each time you want to toggle its contribution or change its color. This makes it easier to evaluate design alternatives and review lighting adjustments in the same scene, though the sources don’t provide a figure for how much render time it might save.

In offices, choosing a grouping method that suits the scene structure helps track which light or group is being adjusted. In Blender, rendering at low intensity and raising it afterward can produce noise, so check light levels before rendering. In Cinema 4D, also account for the possibility that lights with the same name may affect saved results. The documentation doesn’t specify hardware requirements, license types, or compatibility with particular versions, so verify that the feature is available in your setup before incorporating it into your workflow.

Common mistakes

• Adding Light Mix after rendering: Add the channel or element to the scene before rendering.

• Rendering at low intensity and raising the light afterward: According to Blender documentation, this can produce noise; check your starting settings.

• Assuming To Scene applies every item: In Blender, items in the Rest channel are excluded.

• Using duplicate light names in Cinema 4D: Lights with the same name may overwrite saved Light Mix results.

• Using the wrong source in the VFB: The source must be LightMix for Light Mix controls; in the Blender workflow, it changes automatically when rendering starts.