Ray-tracing full Nanite meshes supported in 5.1 preview

For anyone interested: The new UE5 preview does support ray-tracing against the full-quality nanite meshes. It’s activated with ‘r.RayTracing.Nanite.Mode 1’.

Proxy mesh tracing (old limitations)

Full-quality Nanite tracing

Wireframe view.


This is GOLD… Thank you so much… I’ve been dealing with nanite and raytracing reflections for days now. Patchy materials because by default Raytracing does proxy mesh instead of Nanite mesh for it. This solves it. And this is in 5.2 as well.

The strange thing is that if you put this in config ini files it doesn’t register it.

Yep! It’s a pretty good option to have, and the most recent updates to it in UE5_main appear to have cut memory consumption by ~4/5ths in the City demo, so it’s just getting more usable. No idea if it will eventually be efficient enough to replace proxy meshes entirely, but it’s a good utility for those with the VRAM.

As a head’s-up though, it is still definitely experimental. In addition to being borderline unusable on 8GB cards in most scenes I’ve tested, it can suffer from strange corruption issues that make the RT scene completely broken. I can’t consistently make it behave one way or another, but it is what it is.

Thanks for the heads up… will keep an eye on it. I mean I don’t see much if any performance drop when I use it. Probably only video memory but to be perfectly honest not a big deal for what I’m doing.

I just have to use it because Lumen is atrocious on chrome materials. So much blur and from distance it is borderline unusuable so having ray tracing working is the save of a century :slight_smile:

P.S. the ini config does register it I was just a tool and forgot to put = in the ini and not space.


I’m getting this problem with a Nanite mesh (black wire), Baked lighting and Ray tracing reflections. They don’t work, reflections from Nanite meshes are always too bright. I don’t understand why

RT reflections in general are deprecated, so I’m somewhat surprised that they’re working at all. Lumen reflections in 5.3 are the successor system to RT reflections, and should be used.

From what i’ve seen, Lumen reflections look worse than RT reflections. Also, RT ambient occlusion is broken too, when using Static lighting+Nanite.
However, everything works fine when using dynamic lighting + Nanite or static lighting without Nanite.

Lumen reflections shoudn’t look worse than standalone RT reflections if they’re on the same quality level. If lumen is set to software mode and surface cache, it will look worse; if it’s set to Hardware RT and hit lighting for reflections, it will look better.

Quick test:

  1. Lumen reflections (max quality set in PPV)

  1. RT Reflections (not max quality)

Even here the difference is obvious. I can do more tests in a complex scene

I see the stills, but I still don’t understand how RT reflections look ‘worse’ than lumen reflections. the blue glow in lumen reflections is from light-leaking due to their lack of specular occlusion. You may prefer that aesthetically, but it’s less radiometrically accurate than lumen.

I said that Lumen looks worse, not the other way around.

Also, look at the edges. Lumen reflections have a lot of blocky artifacts

Sorry, that was totally my mistake, I meant it the other way around.

Perhaps the image compression is stopping me from seeing it? I’m not really noticing any artifact differences on my machine.

Have you tried upping the Lumen reflection downscale variable? The lower you go (including 0) will decrease upscaling noise.