So I am the author of Luoshuang’s GPULightmass, and I work at Epic now (for ppl don’t know) and I’m also the author of the new DXR GPULightmass.
The new one currently hasn’t got all my old algorithms from Luoshuang’s GPULightmass, and it does more work, so it is much slower.
The new one is able to evaluate material shaders during the bake so material expressions like AbsoluteWorldPosition, per-object painted vertex colors can work. It also switched from radiosity framework to path tracing for massively improved video memory consumption, and in-editor realtime preview. This together with the support of instancing, you should be able to bake large scenes which previously will crash Luoshuang’s GPULightmass. Also path tracing is slightly more accurate than radiosity so you should see fewer artifacts than before. (‘Slightly’ because radiosity’s accuracy increases along with lightmap resolution, so for ppl using super high lightmap res it is almost as accurate as path tracing, and that’s why my Luoshuang’s GPULightmass can beat a lot of path tracing based renderers in terms of quality).
However with the increased workload from evaluating true material shaders + incoherent rays from path tracing, while it is hardware accelerated, it may not reach the speed level of Luoshuang’s GPULightmass even after I’ve migrated all algorithms over (radiosity caching as secondary GI engine, spatial adaptive sampling - a limited form of path guiding). It will be much faster than its current state though.