If you decide to use GPU Lightmass, you basically have to use the community fork (Epic's GPUlightmass - #667 by yujiang.wang) as there are many issues in the one that comes with the engine
If you decide to use GPU Lightmass, you basically have to use the community fork (Epic's GPUlightmass - #667 by yujiang.wang) as there are many issues in the one that comes with the engine