I dont know if I did something wrong. I followed the instruction to setup lightmass GPU render.
I set up the scene with 1 directional light, 1 area light, 1 lightmass portal, 1 lightmass importance volume
Every actor is bump with lightmap res to 512
I also test the GI samples from the GPU lightmass panel to 1024.
The test results for GI is quite bad. The old CPU lightmap rendering would never give this low quality output.