The Progressive GPU Lightmapper is a backend for Unity’s Progressive Lightmapper which uses your GPU and Dedicated Video RAM (VRAM) to generate baked lightmaps and Light Probes.
In order to use the Progressive GPU Lightmapper, your computer must meet these minimum specifications:
If the Scene you are baking requires more VRAM than is available on the designated GPU, bake times can significantly increase. See Performance for information to help you reduce the time it takes to bake your Scene.
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. See Hardware and software requirements.
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, cause it to fail, or even result in the Lightmapper falling back to the CPU if the GPU cannot meet minimum memory requirements. Closing other applications while you are working with this functionality can improve stability and performance.
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.
Switch to a CPU-based denoiser. GPU-based denoisers also use VRAM capacity. Switch to a CPU-based option, like Intel Open Image, which uses system RAM instead.
Use Light Probes for smaller GameObjects. 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 Probes 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.
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.
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: