Post-Render Lighting with V-Ray LightMix: Step-by-Step Use in the VFB

This guide walks through, step by step, how to set up the LightMix render element found in V-Ray for 3ds Max, how to use it in the VFB (V-Ray Frame Buffer), and why it saves time on archviz projects.

What you'll learn

By the end of this article, you'll be able to adjust all the lights in a scene after the fact from a single render file, change light colors and intensities and, if you wish, push those changes back to the actual scene lights — and even open a cloud-rendered EXR file in the VFB and relight it.

Requirements

• V-Ray for 3ds Max (Light Mix was added to VFB2 in V-Ray 5 and is also available in V-Ray 7).

• Access to render settings (Render Setup > Render Elements) or the VFB interface directly.

• Optional: a Chaos Cloud account, for editing cloud-rendered EXR files with LightMix.

Step-by-step setup

1. Add the render element. From the Render Setup > Render Elements tab, click Add... and select VRayLightMix. Alternatively, from VFB > Layers, set the Source to LightMix and add it directly to the scene.

2. Choose a grouping mode. Select one of Instanced lights, Individual lights, Grouped lights, Layers, or Manual light selects. For complex interior scenes, grouping lights like real-world circuit breakers is recommended.

3. Set lights to neutral and bright before rendering. Keeping lights close to white and at high intensity makes it easier to darken them later; rendering at low intensity and boosting it afterward can result in noisy output.

4. Render the scene. Once rendering is complete, select the Source layer in the Layers list on the right side of the VFB and choose Light Mix from the three modes.

5. Adjust the lights. Each listed light has a checkbox (on/off), a Multiplier (intensity factor), and a Color Slot. You can make changes here.

6. Save or push back the result. The To Scene option writes the changes to the actual scene lights (excluding those in the Rest channel); To Composite sends the Light Selects to separate layers for compositing.

The example below summarizes the logic you could follow for an interior scene transitioning from sunset to night mode; this is not a command or code, but a text summary of the application steps:

Common mistakes

• Starting lights too dark: Rendering at low intensity and boosting it in LightMix can increase noise in the image; in this case, you need to write the values back to the scene with To Scene and re-render.

• Starting with colored lights: Leaving lights colored from the start makes it harder to find the correct balance in LightMix; start with neutral white/gray where possible.

• Forgetting the 254-light limit: If a scene has more than 254 individual lights, the first 254 get a separate Light Select, and the rest fall into the Rest channel; this channel may not be saved to file by default, so the 'Include Rest channel when saving to file' option should be enabled if needed.

• Forgetting Self Illumination materials: To include light-emitting surfaces on VRayMtl, VRayLightMtl, or 3ds Max's Physical Material in LightMix, make sure the 'Separate emissive material' option is enabled.

What this means for archviz and interior architecture workflows

LightMix saves time especially for archviz studios and interior architects working with lighting scenarios that change frequently during presentations (day/night, different scene atmospheres). If a client requests an instant lighting change during a meeting, you can intervene live in the VFB without re-rendering. EXR files rendered with Chaos Cloud can also be opened in the local VFB and edited the same way; this is an advantage for remote teams or workstations with modest hardware, since the heavy rendering can be done in the cloud while fine-tuning the lighting happens on the local machine. One point to keep in mind is that Consistent lighting elements mode is automatically enabled by LightMix, as well as how instanced lights created with tools like VRayInstancer or Forest Pack are included in the Light Select render element.

Source and license

This article has been adapted into Turkish and then translated into English from Chaos's official documentation page "VRayLightMix" (documentation.chaos.com) and the official guide "Relight without re-rendering: How Light Mix works in V-Ray 5" (Christopher Nichols) published on the Chaos Blog. Both sources are freely accessible on Chaos's own official channels.