Thats from epic: "Note: Unreal Engine has implemented Apple's Metal API for using their GPUs. However, we have not implemented Metal' ray-tracing functions because Apple has not released any hardware accelerated ray-tracing support so far. The difference between hardware-accelerated ray-tracing and non-accelerated ray- tracing is the difference between rendering a single image in minutes instead of hours. We are researching ways to bring Apple computer users the speed and capabilities of our Path Tracer, so we are not waiting on Apple to solve this problem."