This page provides information on the V-Ray light bake process with V-Ray for Unreal.

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V-Ray Light Bake or just V-Ray Bake is the process of creating lightmaps with complex light interactions and diffuse interreflection using the V-Ray render engine and it's GI and Lighting calculations.



The light bake quality depends on the following:

  • the lightmap resolution of the meshes;

  • the lightmap UVs quality, better unwrapped UVs better bake quality;

  • the V-Ray settings in the settings tab.

Note that actors with vrmeshes assigned will not have their lightmaps baked but will still contribute to the scene for shadows and GI


However, it is possible to import a proxy and bake it with a light map, provided the mesh has correct UV mapping.

Select the proxy and go to Static Mesh > Import Settings rollout. Press the Reset to Default button, which converts the proxy to a static mesh. The static mesh can now be baked.

 Click here to expand for screenshots of the settings...



Please check the following before V-Ray Bake:

  • Read the System Requirements
  • Overlapping/wrapping and/or large amount of polygons in static meshes may result in longer bake times and/or crashes
  • Set GPU Render Device to GPU only if you are using Unreal materials
  • Set all Actors and Light in level to Static



Bake Settings

Below are mentioned all the settings and parameters that modify the quality of the V-Ray Bake.

 V-Ray Bake Settings Tab

Bake Settings

Light bake quality – A slider for a set of quality presets.

0 - Preview - Progressive Image Sampler; minSubdivs - 8; maxSubdivs - 32; Sample Limit - 100; Noise threshold - 0.3; Light Cache subdivs - 300; Retrace - 2; Denoiser -Strong denoising with strength 2 and radius 15

1 - Medium - Bucket Image Sampler; minSubdivs - 8; maxSubdivs - 32; Sample Limit - 1000; Noise threshold - 0.1; Light Cache subdivs - 1200; Retrace - 4; Denoiser -Default denoising with strength 1 and radius 10

2 - High - Bucket Image Sampler; minSubdivs - 8; maxSubdivs - 32; Sample Limit - 2000; Noise threshold - 0.005; Light Cache subdivs - 3000; Retrace - 8; Denoiser -Default denoising with strength 1 and radius 10

Lightmap Atlas resolution – Sets the preferred atlas resolution. Note that static meshes that have larger Light Map Res will automatically resize the atlas.

DilationThe number of pixels to expand around geometry UVs.

Export VRScene – Enables the export of a .vrscene file when the V-Ray Bake  button is clicked.

Export VRScene Path – Directory where the .vrscene file is saved with the file name bake#.vrscene. Default directory is <Project_Path>

(plus) NEW - Export EXR – Enables the export of a .exr  file for each Static mesh Actor in the level when the V-Ray Bake  button is clicked.

(plus) NEW - Export EXR Path – Directory where the .exr files are saved with the file name <StaticMeshActor_Name>.exr. Default directory is <Project_Path>/export

(plus) NEW - Override Light Maps – Enables the loading of .exr  files for Static Mesh Actors in the level when the V-Ray Bake  button is clicked.

(plus) NEW - Override Light Maps Path – Directory from where the .exr files are loaded when the V-Ray Bake  button is clicked. Default directory is <Project_Path>/override.

If you want to rebake only selected actors in the level then delete the appropriate .exr  files (<StaticMeshActor_Name>.exr) from the directory specified in the Override Light Maps Path. When you click the V-Ray Bake  button, only the Actors that do not have according .exr  files will be baked and atlases for the other actors will be loaded from the Override Light Maps Path folder.

Only Static Meshes that do not have appropriate .exr files in the directory specified in the Override Light Maps Path will be included in the baking process.

Large Atlas Resolution values speed up light baking but increase memory consumption.





 V-Ray Settings Tab

Camera Settings

Auto Correction Mode – Specifies which camera to use the automatic exposure and white balance setting.

All cameras
Cameras without exposure only

Auto Exposure – Automatically determines an appropriate exposure value for the render. It requires Light Cache to be set as a GI engine and Interactive turned off.

Auto White Balance – Automatically determines a suitable white balance value for the image. It requires Light Cache to be set as a GI engine and Interactive turned off.

Auto Exposure and Auto White Balance work only when using Light Cache as GI solution.


Render Settings

Time Limit (Minutes) – Specifies the maximum time (in minutes) for refining the image.

Global Illumination

GI Engine – Specifies the type of secondary engine. Note that Brute force is always used as a primary engine.

Brute Force

GI Depth – The number of bounces for indirect illumination.

Light Cache

Environment – Specifies which VRaySettingsEnvironment blueprint will be used at render time for environment overrides. Blueprint must be picked from the level and assigned using either the drop-down list or the picker.


Shadow Bias – A global parameter for lights. This value moves the shadow toward or away from the shadow-casting object (or objects). Higher values move the shadow toward the object(s) while lower values move it away. If this value is too extreme, shadows can "leak" through places they shouldn't or "detach" from an object.


Fallback Material – Specifies what material to be used at render time for unsupported materials. If the slot is empty actors that have unsupported materials assigned will be rendered transparent.

Fallback Material only works with V-Ray Material Instances

VRay CUDA Device Select

You may not want to use all available GPU devices for rendering, especially if you have multiple GPUs and you want to leave one of them free for working on the user interface or you may want to combine your CPU and GPU together. Enable the desired render device by ticking the checkbox.

We recommend in situations when the video memory of the graphics card is insufficient to use only the CPU as a rendering device. This way you will use the system RAM instead of the VRAM of the graphics card.

Distributed Rendering

On – Enables or disables distributed rendering for V-Ray for Unreal. Use the Render Servers list to specify the machines that will be used for distributed rendering.

 Use Local Host – When enabled, the client machine (the one from which the user initiates the DR render) will also take part in the rendering calculations. If disabled, the client machine only organizes the DR process, sends rendering tasks to the render servers and displays the final result.

Render Servers – Specifies the render servers. Click the + button to manually add a server by entering its IP address or network name followed by its port number (default is 20207) (e.g.

Maximum cached asset size (in GB) – This option specifies the maximum assets cache size limit in GB on the render machines. When the size of the assets on a render server exceeds the specified amount, least recently used assets are automatically deleted at the end of each render until the folder size is less than the limit.





Usage Examples

In this short example, a .vrscene file is loaded. Before we bake the lighting we first make sure that all lights in the scene are set to Static. Next we click on the Bake button in the V-Ray drop-down. The VFB pop up and the lightmaps begin to render. When it is done they are encoded and imported into Unreal. Finally, we start the IPR rendering and start walking around to see the parity between the lightbake and the actual render.