I’m using Lumen in UE5 for nice reflections on a water surface, and usually it’s reflecting the landscape around the water really nicely.
However, when I move an object in front of the landscape, whatever is behind that object no longer gets reflected, and there are ugly bright patches left behind where there should be landscape reflected (see screenshot).
I imagine this is because the reflection is in screen space, and the object is occluding the landscape in screen space so Lumen doesn’t know what to reflect there.
Is there anything I can do to fix these artifacts while keeping it real-time and not using the deprecated raytracing reflection mode?
Look at the section about large worlds. Lumen, like basically all raytracing, has a limited trace distance for performance reasons. After this distance is exceeded, it will use screen tracing. Your landscape is too far away and thus isn’t being included in the Lumen Scene. The documentation talks about dealing with it, but in some cases you may have to live with it for performance reasons.
NOTE: if you have low/medium reflection setting in engine scalability settings, Lumen will use Screen Space instead of… Lumen reflection. It took me while
