Lumen performance vs Raytracing

Downloaded the UE5 EA this evening as I’m excited to play with the new features. I’ve been working on various projects using raytracing lately and converted some of my projects over to UE5 and switched from RT to Lumen.

Is it expected that Lumen should have worse performance than raytracing? Examples are

Archviz style room:
RT: ~60fps, Lumen: ~45fps

Stylised village scene:
RT: ~47-50fps, Lumen: ~20-25fps

This is on a 3090 RTX and feels relatively low, though I have no idea what my expectations should be.

I had a play with some Lumen settings and also noticed Use Hardware Ray Tracing when available seems to make no difference to the framerate/time. Is there a way to confirm that Lumen is using hardware raytracing on my system? Is the option just not working/hooked up to the backend at the moment?

Any advice on Lumen performance, what to expect and how to optimise (other than what’s in the documentation - already scanned through that) would be great.

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Lumen GI seems to be expensive, but nowhere near as expensive as rtgi.

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In my case (GTX1660) Lumen works faster than Ray Tracing, but the quality is a whole different story.

That was my expectation (and I thought the point in Lumen) - that Lumen would be expensive, but not as bad as rtgi. Tried a few more projects now though and definitely getting longer frame times and lower fps when using Lumen.

I’m wondering if something’s not quite working right in EA with my card or Nvidia drivers. Mainly because turning hardware RT Lumen support on and off doesn’t affect framerate or draw time at all.

A 1160 doesn’t just Explode when you turn on Ray Tracing? lol

Nope. If you know what you do, you can have RT shadows and reflections and decent frame rate.

… decent at what resolution?
The target is 4k. Not 1080p.
Yea you can get it to run ok at 1080p, maybe…

My target is 1080p and I get decent fps at that resolution. The rest is irrelevant.

Or your resolution is irrelevant.

Most if not all of us develop for 4k and up, given it’s the new standard for consoles too…

Do you mean the quality is worse with Lumen? I haven’t gotten around to testing both back and forth yet.

Having another read of the documentation about Lumen, it’s not really clear if hardware RT is used for everything when capable hardware is found, or just for things that need it (ie. skeletal or morphing meshes). I wonder if that could explain the lower fps in Lumen than RTGI with my 3090 if Lumen is software RTing the distance field meshes still.

Yes. RT reflections and GI look better that Lumen. Besides that Lumen is kind of mixture of screen space / world space techniques and because of that you get all those related limitations and glitches. But… even with all that Lumen is way better than anything (except proper RT) that other engines have to offer. Lumen is kind of like SVOGI (Cryengine 5) on steroids.

How do you enable raytracing on a none RTX card!?

4K is performance heavy in resolution, it’s to no surprise that it runs poorly on your end.
If consoles only allow 4K resolution, than you have to downscale the graphical quality of your project.

Lumen is in early acces and by far not finished, RTX is not even supported on consoles yet and is incredibly heavy (depending on your settings ofcourse).

Nvidia enabled ray tracing support for selected GTX 10 series and GTX 16 series cards a long time ago. If you have one of those cards, then RT is available for you in UE4/5.

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Oh i didn’t know about that, interesting.
Still wouldn’t want to enable it for those card though, as i’m sure the performacne sucks.

Depends on what you enable.
Initially you loose fps, but if you change stuff around to say only raytrace shadows, it can perform ok and also look better.
As always it’s a balancing act.

As I said several times 4k is already an old standard.
If you publish or intend on publishing a game on pc the minimum you can do is get to 60fps on a 1080ti.

It’s been done, in older versions of UE4, consistently, by a ton of companies.

Surely it will eventually be possible with ue5 when the release is not the equivalent of a pre-alpha… currently, doesn’t seem lilely.
It’s not exactly likely in .26 either.

Look through the documentation on Lumen, it’s not just a plug and play option. To get the best out of it there’s some work you need to do and there are some limitations.

Its more RT slightly enhanced lumen, not full RT on some parts. This is shown more clearly in reflections.

That depends of what you do with UE4/5. I’m not a game developer and I couldn’t care less about 4k, 60 fps and other similar things. So, in my case possible low performance is not an issue. I’ll take 10 frames per second in UE4/5 over 10 second per frame in offline renderers any day.