In brief
- LightMix is a light-editing tool integrated into Corona's Virtual Frame Buffer that lets you change light intensity and color without re-rendering.
- Each LightSelect layer consumes RAM proportional to render resolution, so grouping lights is critical.
- LightMix values set at low resolution can be 'baked' into the scene and then re-rendered at full resolution.
- Because Corona's .CXR format stores all LightMix data, revisions can be made months later in Corona Image Editor without opening 3ds Max.
LightMix, the tool Chaos developed for Corona Renderer, remains one of the most practical solutions for architectural visualization (archviz) studios looking to save time in interior presentations. In a guide shared by archviz artist Olena Kamenetska on the Chaos blog, LightMix's setup, grouping strategy, and RAM management are explained step by step. The tool works integrated into Corona's Virtual Frame Buffer (VFB) for both 3ds Max and Cinema 4D, allowing light intensity and color to be changed even after the render is complete.
How does LightMix work?
When LightMix is enabled, Corona generates a separate "LightSelect render element" layer for each light or light group alongside the main "beauty" pass. The CShading_LightMix element combines these layers into the composite image in the VFB. Moving the sliders in the VFB effectively changes how much each of these layers contributes to the composite; since the render data already exists, no re-render is needed.
This method isn't just a post-render tool; it can be used both in production rendering and in Interactive Rendering (IR) mode.
Setup: automatic or manual?
The fastest way to set up LightMix is the automatic option:
Go to
Render Setup › Scene tab › General Settings.Click the "Setup LightMix" button.
In the dialog that opens, decide whether hidden lights should be included ("Add hidden lights") and whether denoising should be applied to the LightMix elements ("Included in denoising").
When you press "Generate," Corona automatically adds the CShading_LightMix element and a CShading_LightSelect element for each group (including the environment light/HDRI).
Those who want finer control can opt for manual setup:
A CShading_LightMix element is added via
Render Setup › Render Elements.A separate CShading_LightSelect element is added for each light group you want to control independently.
The lights to be included in each LightSelect element are determined via the "included light sources" list.
On at least one LightSelect, the "include lights not assigned to other LightSelect passes" option should be enabled so that unassigned lights are collected into a "Rest" group, otherwise some lights may be missing from the composite.
Grouping strategy
The setup dialog allows grouping lights in four different ways:
| Grouping type | Description |
|---|---|
| Instances | All instances of the same light object in a single layer |
| Groups | Lights grouped according to 3ds Max groups in a single layer |
| Layers | Lights on the same scene layer in a single layer |
| Individual lights | Each light in its own layer |
Kamenetska notes that in interior projects, she pre-groups lights in the scene with meaningful names like "Pendants," "Floor Lamps," "Sun & Sky," and "Recessed Downlights," then uses the "Groups" option; this approach works well in live client presentations since it offers meaningful sliders in the VFB instead of 40 anonymous light names. According to the author, the few minutes spent naming and grouping lights pays for itself many times over in every subsequent live editing session.
RAM management and bake workflow
Each LightSelect element consumes RAM proportional to render resolution and bit depth; at 4K resolution, 30 independent lights can easily push memory limits. The setup dialog shows the estimated RAM usage per layer, and it's recommended to take this estimate seriously. The recommended workflow for high-resolution final renders is as follows:
Set up LightMix values at a low resolution (e.g., 1920×1080).
Once you're satisfied with the light values, click the ">Scene (Bake)" button in the LightMix tab of the VFB to save the values to the actual lights and light-emitting materials in the scene.
Disable all LightMix and LightSelect render elements.
Re-render at full resolution without this extra memory overhead.
Implications for architectural visualization workflows
For architecture firms and archviz artists doing interior presentations, LightMix makes it possible to resolve client revisions in minutes instead of hours. Kamenetska reports producing a night version from a completed daytime render in about three minutes. Important note: this feature only works within Corona Renderer, and VFB 2.0 arrived with Corona 12; those still using the old VFB can switch via Render Setup › System › System Settings › VFB Settings. Additionally, saving the .CXR format for every important render allows revisions to be made via Corona Image Editor without reopening the 3ds Max file; this saves disk space and time, especially when a client asks months later, "Could you turn off this lamp?"
Sources
3 sourcesSource texts are not republished; short quotes are marked, everything else is our own summary and commentary.
For interior architecture and archviz studios in Turkey, LightMix is a tool that can provide serious time savings in client revision processes. Especially in residential and commercial interior projects where requests for different times of day and moods are frequent, presenting day-night-golden hour scenarios from a single render within minutes has a positive effect on both client satisfaction and render farm costs.
However, one point to watch is RAM consumption: enabling many independent light layers at high resolution can cause the render to crash, especially on workstations with limited memory. Adopting the workflow of setting values at low resolution and baking them, along with archiving the .CXR format, both reduces hardware load and allows for quick responses to revision requests that come in months later.
Frequently asked questions
What is LightMix and which render engine does it belong to?
LightMix is a feature integrated into Chaos Corona Renderer's Virtual Frame Buffer; it allows you to change the intensity and color of lights during or after rendering without re-rendering.
How do I avoid RAM issues when using LightMix?
Set up at a low resolution, determine the light values, then save them to the scene using the '>Scene (Bake)' button in the VFB, disable the LightMix elements, and re-render at full resolution.
What is the CXR file used for?
Corona's .CXR format stores all render elements, LightMix data, denoising information, and post-processing settings in a single file; this allows revisions to be made via Corona Image Editor even months later without opening 3ds Max.
