In most configurations, the Progressive GPU LightmapperA tool in Unity that bakes lightmaps according to the arrangement of lights and geometry in your scene. More info
See in Glossary performs much faster than the Progressive CPU Lightmapper. The performance depends on the selected Baking Profile.
However, the specifications of the GPU you use to bake and the amount of VRAM dedicated to that GPU both influence your experience of the lightmapper’s performance.
Other applications competing for GPU resources also have an impact on baking performance. Depending on your hardware vendor, reductions in the amount of VRAM available to Unity can slow down the bake process or cause it to fail.
In order to achieve results of the same quality as the Progressive CPU Lightmapper, the Progressive GPU Lightmapper needs up to four times more indirect light samples. The Progressive CPU Lightmapper uses an approach called branched path tracing, which launches more light rays at each bounce. The branched path tracing approach is not suitable for GPUs.
Unity provides a spreadsheet to help you determine how much memory the Progressive GPU Lightmapper needs to bake your sceneA Scene contains the environments and menus of your game. Think of each unique Scene file as a unique level. In each Scene, you place your environments, obstacles, and decorations, essentially designing and building your game in pieces. More info
See in Glossary. For more information see the Progressive GPU Lightmapper Memory Spreadsheet .
The Progressive GPU Lightmapper includes a feature called lightmapper tiling. Lightmapper tiling prevents the Progressive GPU Lightmapper from using all available GPU memory. Instead, Unity allocates some temporary memory on the CPU, then bakes your lighting in tiles that are sized to match the amount of GPU memory available. Unity configures the tiling based on the selected Baking Profile. The Progressive CPU Lightmapper does not include a tiling feature.
When the tiling feature is active, and when the lightmapA pre-rendered texture that contains the effects of light sources on static objects in the scene. Lightmaps are overlaid on top of scene geometry to create the effect of lighting. More info
See in Glossary atlas resolution is 512px or bigger, the baking process is likely to be slower than baking the same scene without tiling.
On macOS it is more difficult to determine how much memory is available. As a result, fallback to CPU is more likely on this platform and it is a best practice to follow instructions for optimizing your bake speed.
There are several ways you can reduce bake times and avoid situations where bakes exceed the VRAM available to the GPU designated for baking.
Close other GPU-accelerated applications. GPU-accelerated 2D image editing and 3D modelling software uses VRAM. Turn off accelerated graphics functionality or quit these applications.
Use Light Probes for smaller GameObjectsThe fundamental object in Unity scenes, which can represent characters, props, scenery, cameras, waypoints, and more. A GameObject’s functionality is defined by the Components attached to it. More info
See in Glossary.
GameObjects such as debris or small props use up space in lightmaps but might not contribute significantly to the look of a scene. To optimize bake speed, disable Contribute Global Illumination for these GameObjects’ Mesh Renderers and light them with Light ProbesLight probes store information about how light passes through space in your scene. A collection of light probes arranged within a given space can improve lighting on moving objects and static LOD scenery within that space. More info
See in Glossary instead.
Designate separate GPUs for rendering and baking. If your computer has more than one GPU, you can designate one for rendering and one for baking. See Configure GPU selection below.
Use a lower number of Anti-aliasing samples. The default value for this setting in the Lightmap Parameters Asset is 8. When you increase it, Unity uses more VRAM. When you are using a lightmap size of 4096 or above, this can quickly exceed the memory of many consumer GPUs.
Use fewer samples (Direct Samples, Indirect Samples, Environment Samples) and use the Denoiser to clean up the remaining noise in the lightmap.
Reduce your lightmap resolution.
If you have at least two GPUs, you can specify one GPU for rendering the Scene and another for baking lighting. This might be desirable in cases where there is insufficient VRAM available for the default GPU to both render your scene and bake it using the Progressive GPU Lightmapper.
To change which GPU Unity uses for baking: