How do i update an unreal engine 4 level to perform well with ue5 nanite and lumen?

Development Rendering
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How do i update an unreal engine 4 level to perform well with ue5 nanite and lumen? After I set all of my static meshes to use nanite… it still runs like a buggy 5 fps mess. Basically the problem seems to lie in “Virtual Shadow Map Page Overflow detected”… All the shadows look like blocky FLICKERING messes. Upping it to 8k does nothing. So the question is wtf is going on? What can i do to properly update my level. I have tried copying everything and pasting it into a new open world level with no improvement…

I do currently use virtual shadow maps and wish to continue doing so … so i need to understand how to fix this.

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How big is your level? Have you split it up into partitions using World Partition?

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its a good amount of buildings and lights. typical deathmatch type of level. Started with sub levels in ue4… brought it to ue5… tried copying and pasting it all into 1 brand new world level… same crap results.

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4

Nice!

Did upping the r.Shadow.Virtual.MaxPhysicalPages to 8000 get rid of the error message though?

Is your “Raytraced Shadows” option in the render section turned off?

Maybe just copy/paste small bits at a time into a new level to see when the performance tanks…

There are known bugs with the VSM but you should be able to get way better performance than that (what hardware are you using?)

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if i delete all the lights performance goes up to 70-90 fps (im running dual 3090s so kind of expected more from nanite). i tried disabling raytracing all togehter in project settings which did nothing. And no… setting r.Shadow.Virtual.MaxPhysicalPages to 8000 does not fix the problem. It does make it look a little nicer, but the problem is still there all the time and the fps still low.

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try the console command:

ShowFlag.GlobalIllumination 0
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doesnt help at all

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What kind of hardware are you using?

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dual 3090s… 32 thread processor… though i have not enabled the dual 3090 for this project… just using hte 1 3090.

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You should be getting higher frame-rates for sure (sorry, saw you mentioned the 3090s).

Just for the sake of completeness - you have enabled “hardware lumen”?

You could try changing the “Scalability” types to note the differences there too.

Have you gone through looking at the stats? “stats unit” is a good place to start (from the console) - you will hopefully find there is one area that’s taking most of the time - it’s just a matter of tracing through to find it’s cause…

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i mean its the lights that kill it all… virtual shadow maps have it flickering at 10-13 fps… and if i disable virtual shadow maps… its basically frozen… or 1 fps lol…

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Also keep in mind im running it at 4k resolution

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That probably doesn’t help - what about using TSR or DLSS to reduce the res?

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Its not the issue regardless so i wont focus on that. I just went back to the version where the sublevels are still in play… and i hid 19 out of 20 of hte sublevels…(basically now only 1 room with like 20 lights in it…) and although the fps go up gradually to 70 fps… it still has the "Virtual Shadow Map Page Overflow detected” error… something clearly wrong but i dont understand what.

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I haven’t got to optimizing lights in my level yet, but I’ve made note of the following tips when reading posts here:

  • lumen quite possibly doesn’t like as many lights as you have.
  • If possible, use emissive materials instead of lights
  • use the MaxDrawDistance and MaxDistanceFadeRange values for each light to limit their rendering distances
  • Pool lights and unpool at a certain distance (rdInst is a plugin I wrote that does actor pooling and ISMs)
  • Build room interiors including their lights as “generic” and move them around the level when you enter buildings (rdBPtools is another plugin :slight_smile: )
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even with lumen turned off the problem remains.

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I’ve just tried editing my level at 4K - it’s 50km2 and running on hw lumen with VSM - GI is down to low while editing (plus 5.2 has slowed that down) but everything else can be medium or high. (rtx 3070ti and i7)

It runs almost as fast at 4K as 2K - around 75FPS - the VSM shadows are very nice (as is the nanite)

I then tested by adding 25 lights - it dropped by 25fps - it has to be the lights:

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u think its a bug in 5.2? Plus in my level… lot of the lights are far away… its not like they should all be in use… i mean my fps is down when im in a room that only sees 2 lights… but renders like they are all in view.

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There’s definitely something not right - whether or not it’s a bug or not, it’s still hard to tell.

What happens if you disable VSM (just for testing)?

Does running this console command help with the flickering?

r.Shadow.Virtual.ResolutionLodBiasDirectional 1
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r.Shadow.Virtual.ResolutionLodBiasDirectional 1 gives no improvement.

If i disable virtual shadow maps the performance gets way worse because now its just a bunch of dynamic casting shadow lights… so the fps drops even lower… in fact i just made it crash unreal by doing that after a few seconds and turning the camera to reveal more of the scene.

My scene has several hundred lights… whats funny is setting it all to raytraced lighting basically runs almost the same speed with teh warning 626 lights skipped… because max count is 256. that 10-15 fps…