Hi all, I’m really enjoying playing around the Lumen and really excited to see how it develops over time.
Maybe I missed some launch notes (I’ve read through the Lumen documentation and can’t see anything about this issue) but it seems I can’t enable raytraced shadows and Lumen at the same time. I can enable raytracing for the project, and Lumen seems to be using hardware for itself, but when I actually enable raytraced shadows (r.RayTracing.Shadows 1 in console) the editor crashes and I get a message stating the GPU crashed.
This is a converted UE4 project, so that could have something to do with it.
Has anyone else had any luck using both raytraced shadows and Lumen at the same time - all the videos I’ve seen so far on Youtube are playing it safe and sticking with rasterised shadows.
I’m can turn on raytraced shadows and Lumen fine without a crash, but I’m also not sure Lumen is quite working for me (worse performance than RTGI, and toggling Lumen hardware RT on and off makes no difference to fps)
Are you sure it’s rendering raytraced shadows and not the new ‘virtual shadow maps’? You can check under Project Settings > Rendering > Shadows. These look similar to raytraced shadows, but use mesh distance fields instead of actual geo I think.
I think the performance is dependent on the conditions and comparison you’re making. Running full global illumination (including processing the skylight and having having any light bounces at all) with raytracing for me, tanked my fps running on a 2080ti. Lumen is giving me usable (but not ideal) fps but offering the same feature set as full raytraced gi (just minus some quality in reflections and accuracy).
To my knowledge there was no raytraced solution that could offer anything above a single light bounce in realtime that ran at a playable framerate (60fps or above at 1080p).
Another semantic argument is that Lumen is a raytracing solution, just one that’s heavily optimized by using cards instead of raw rays.