# Lumen no longer working in UE5.5 DX11 SM5

**URL:** <https://forums.unrealengine.com/t/lumen-no-longer-working-in-ue5-5-dx11-sm5/2126402>\
**Category:** Rendering\
**Tags:** dx11, unreal-engine, Lumen\
**Created:** [November 16, 2024, 12:43am UTC](https://forums.unrealengine.com/t/lumen-no-longer-working-in-ue5-5-dx11-sm5/2126402 "2024-11-16T00:43:37Z")\
**Posts on this page:** 20\
**Page:** 1

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**Author:** ![Uno1982](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/uno1982/32/982436_2.png) [@Uno1982](https://forums.unrealengine.com/u/Uno1982)\
**Post date:** [November 16, 2024, 12:43am UTC](https://forums.unrealengine.com/t/lumen-no-longer-working-in-ue5-5-dx11-sm5/2126402/1 "2024-11-16T00:43:37Z")

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UE5.4 Lumen working with DX11 and SM5 which was an really fast and awesome pipeline for non nanite traditional LODs and lower end hardware

 ![image](https://d3kjluh73b9h9o.cloudfront.net/original/4X/3/6/b/36bb7152fdef8d271c7cf405191ac0e915cdc4e4.jpeg)

120FPS Default settings other than DX11 and SM5 (would be more but im capped to my monitor htz in this screenshot)

 ![image](https://d3kjluh73b9h9o.cloudfront.net/original/4X/1/3/5/1350d63ab3b49e88b1f1a82a5ec02b408242fff0.jpeg)

Same project migrated to UE5.5 without any changes. You can see it no longer works.

 ![image](https://d3kjluh73b9h9o.cloudfront.net/original/4X/4/2/7/427bbd34b59b8e5f0d5e710bdad640947fccc273.jpeg)

UE5.5 with DX12 and SM6

 ![image](https://d3kjluh73b9h9o.cloudfront.net/original/4X/d/9/f/d9f720a11c2f627f1f0e6b9327c0a13c0c9980c5.jpeg)  
a 20+ loss in frames due to added overhead.

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**Author:** ![jblackwell](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@jblackwell](https://forums.unrealengine.com/u/jblackwell)\
**Post date:** [November 16, 2024, 1:18am UTC](https://forums.unrealengine.com/t/lumen-no-longer-working-in-ue5-5-dx11-sm5/2126402/2 "2024-11-16T01:18:35Z")

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Both DX11 and SM5 for lumen were deprecated, a while ago I think- I don’t think they’ll be coming back; although frankly, your perf numbers are something remarkable.

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<div class="post-metadata">

**Author:** ![Uno1982](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/uno1982/32/982436_2.png) [@Uno1982](https://forums.unrealengine.com/u/Uno1982)\
**Post date:** [November 16, 2024, 1:26am UTC](https://forums.unrealengine.com/t/lumen-no-longer-working-in-ue5-5-dx11-sm5/2126402/3 "2024-11-16T01:26:23Z")

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[![](https://d3kjluh73b9h9o.cloudfront.net/original/4X/b/f/e/bfe5c30de6118353bf64669a98c11233bfe8f1a6.jpeg "UE5.5 - Lumen no longer working in DX11 (SM5)") ](https://www.youtube.com/watch?v=Vsw0X9HHDZo)

It was working in 5.4 and as I showed here SM5 lumen support is mentioned in the release notes and the official docs. Nanite was deprecated to SM6 due to Virtual Shadow maps. Lumen has been working in DX11 as of 5.4.4

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<div class="post-metadata">

**Author:** ![Uno1982](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/uno1982/32/982436_2.png) [@Uno1982](https://forums.unrealengine.com/u/Uno1982)\
**Post date:** [November 16, 2024, 1:29am UTC](https://forums.unrealengine.com/t/lumen-no-longer-working-in-ue5-5-dx11-sm5/2126402/4 "2024-11-16T01:29:35Z")

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5.5 release notes even mention SM5 Lumen support.

 ![image](https://d3kjluh73b9h9o.cloudfront.net/original/4X/1/e/f/1ef03d4f7608a2b7534da2dfcfd68f6f6d55b91e.png)

 ![image](https://d3kjluh73b9h9o.cloudfront.net/original/4X/7/4/a/74a75b96c067d9eb13bc2c8001fa1c4bc0d819a8.png)

> [@jblackwell](#):
>
> Both DX11 and SM5 for lumen were deprecated, a while ago I think- I don’t think they’ll be coming back; although frankly, your perf numbers are something remarkable.

Nah we have it running on APUs and really cheap non HWRT pixel streaming machines from 5.1 - 5.4

its literally the way to get performant GI in UE5 (GTX 1070 my guy … not even RTX)  
I track source changes and I’m almost for certain the Fortnite and UEFN DX12 requirement likely got pushed into UE5.5 main and it was an unintended side affect.

Wouldn’t be the first time I’ve seen this.

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**Author:** ![jblackwell](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@jblackwell](https://forums.unrealengine.com/u/jblackwell)\
**Post date:** [November 16, 2024, 5:16pm UTC](https://forums.unrealengine.com/t/lumen-no-longer-working-in-ue5-5-dx11-sm5/2126402/5 "2024-11-16T17:16:32Z")

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Well, the more you know I suppose. I knew academically that handmade LODs and the older render path _could_ improve lumen throughput, but I’m still really impressed by your numbers. Even with how much better 5.5 runs, it’s still significantly behind what you’ve achieved. I feel like I know someone who would be very interested in this behavior.

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**Author:** ![Uno1982](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/uno1982/32/982436_2.png) [@Uno1982](https://forums.unrealengine.com/u/Uno1982)\
**Post date:** [November 16, 2024, 5:50pm UTC](https://forums.unrealengine.com/t/lumen-no-longer-working-in-ue5-5-dx11-sm5/2126402/6 "2024-11-16T17:50:58Z")

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Yeah its completely swept under the floor which is a failure to market and communicate true optimization paths in my opinion… Even today in UE5.5 look at this.

DX11 SM5 - 4.26ms starting cost (235fps)

 ![image](https://d3kjluh73b9h9o.cloudfront.net/original/4X/d/5/6/d56f2071b522c614c36916a3f4880314d1884795.jpeg)

DX12 SM5 - zero changes other than rhi results in (but why even run dx12 with sm5?)  
Note: **the memory footprint difference**

 ![image](https://d3kjluh73b9h9o.cloudfront.net/original/4X/b/4/d/b4d10fa6bb68628c37d5a3bcb75afad8ff7e4ff9.jpeg)  
29% drop for literally nothing

DX12 SM6 - zero change other than lumen is now enabled since its locked behind sm6

 ![image](https://d3kjluh73b9h9o.cloudfront.net/original/4X/7/5/8/758e87e6a9bd0f09dfa2f820e03362927cbadc0c.jpeg)  
Another 73% drop from DX12 SM5.

That’s a total loss of about 123% of the initial starting ms  
I feel this is a failure to capitalize on an area where so many ppl who have asked and been yelling that UE5 is too heavy could have simply been told (fall back to dx11 as older hardware drivers and chips are better suited for dx11 and sm5)

It all honesty it was our “secret weapon” for running really cheap pixel streaming instances with Lumen SWRT GI without the need for HWRT capable machines… this change really hurts our business model. Direct impact on operating cost. With the starting overhead budget we could squeeze 4 users per instance in with no issues… We will be lucky to hit 60 fps with lumen now with 2 users per instance unless we go g5 and thats pretty sad.

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**Author:** ![weirdload1](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@weirdload1](https://forums.unrealengine.com/u/weirdload1)\
**Post date:** [November 16, 2024, 8:35pm UTC](https://forums.unrealengine.com/t/lumen-no-longer-working-in-ue5-5-dx11-sm5/2126402/7 "2024-11-16T20:35:06Z")

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This affects me too! I have had the same problem with poor performance and video memory issues when using DX12 in my project, and I saw the difference immediately when migrating my project to 5.5, since I’m using Lumen to illuminate everything, including interiors - using skylight leak to brighten room interiors. My game looks AWFUL now! Luckily I backed my project up before migrating it. I’m hoping this is an oversight, as OP said that continued support for Lumen under DX11 is in the update notes, so I guess I’ll give it some time before deciding whether to roll back to 5.4, or start trying to optimise for DX12 in 5.5. Luckily my game is a passion project with no time limit on it. I imagine actual devs with this same issue must be fuming right now…

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<div class="post-metadata">

**Author:** ![jblackwell](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@jblackwell](https://forums.unrealengine.com/u/jblackwell)\
**Post date:** [November 16, 2024, 11:17pm UTC](https://forums.unrealengine.com/t/lumen-no-longer-working-in-ue5-5-dx11-sm5/2126402/8 "2024-11-16T23:17:44Z")

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It’s funny- most of the people I know working with lumen have taken DX12 and SM6 as a given- I don’t think a lot of people saw that older path as technically optimal, although that was largely because workflow needs superceded performance. It’s a massive bummer that the regressions are so substantial, although I’m confused as to exactly _why_ you need to upgrade from 5.4 to 5.5?

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**Author:** ![Jinkel](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/jinkel/32/998041_2.png) [@Jinkel](https://forums.unrealengine.com/u/Jinkel)\
**Post date:** [November 17, 2024, 2:12am UTC](https://forums.unrealengine.com/t/lumen-no-longer-working-in-ue5-5-dx11-sm5/2126402/9 "2024-11-17T02:12:24Z")

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I use DX12 SM6 but have the same performance issue 👇  
[Link](https://forums.unrealengine.com/t/unreal-engine-5-5-released/2117936/29)

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<div class="post-metadata">

**Author:** ![Uno1982](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/uno1982/32/982436_2.png) [@Uno1982](https://forums.unrealengine.com/u/Uno1982)\
**Post date:** [November 17, 2024, 8:06am UTC](https://forums.unrealengine.com/t/lumen-no-longer-working-in-ue5-5-dx11-sm5/2126402/10 "2024-11-17T08:06:17Z")

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Because eventually third party APIs and frameworks update and older versions become abandoned. Look at openvr vs openxr, Android support for ue4.27, Google play, webrtc standandards etc. while we “can” just stop on 5.1 as it’s currently our prod version it becomes a liability to keep an application running on older engine versions. I’ve been tracking pixel streaming memory leaks across 3 minor versions now looking to move to either 5.4 or 5.5 but it does appear we will have to wait or overcome other issues as it looks like pak chunking isn’t working in 5.5 like it did in 5.4 either and that’s primarily how we build our our room loader for our cloud app.

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<div class="post-metadata">

**Author:** ![Uno1982](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/uno1982/32/982436_2.png) [@Uno1982](https://forums.unrealengine.com/u/Uno1982)\
**Post date:** [December 10, 2024, 4:52pm UTC](https://forums.unrealengine.com/t/lumen-no-longer-working-in-ue5-5-dx11-sm5/2126402/11 "2024-12-10T16:52:30Z")

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Just a follow up here that even though it was mentioned that a flag was in main it appears it didn’t make it into 5.5.1

> [@5.5.1 Hotfix Released](https://forums.unrealengine.com/t/5-5-1-hotfix-released/2194649):
>
> The 5.5.1 Hotfix is live—snag the latest update for a selection of fixes. Please feel free to share feedback and discuss the current version in the release topic, [Unreal Engine 5.5 Released](https://forums.unrealengine.com/t/unreal-engine-5-5-released/2117936). If you experience a bug with the 5.5.1 Hotfix, please follow the [How to Report a Bug](https://www.unrealengine.com/support/report-a-bug) guide to report it on the [Bug Submission Form](https://epicsupport.force.com/unrealengine). Issue Summary UE-230698 Crash when creating a child blueprint based on a dirty blueprint UE-229712 MovieGraph: Crash when using BurnIn + 32 Bit PPM to Single Laye…

> [@Lumen GI and Reflections feedback thread](https://forums.unrealengine.com/t/lumen-gi-and-reflections-feedback-thread/501108/2010):
>
> I’ve exposed r.Lumen.Supported.SM5 in UE5-Main, which you can integrate in order to re-enable DX11 support. Maybe will be able to get that into a hotfix.

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<div class="post-metadata">

**Author:** ![Uno1982](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/uno1982/32/982436_2.png) [@Uno1982](https://forums.unrealengine.com/u/Uno1982)\
**Post date:** [January 28, 2025, 6:36pm UTC](https://forums.unrealengine.com/t/lumen-no-longer-working-in-ue5-5-dx11-sm5/2126402/12 "2025-01-28T18:36:01Z")

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> [@Lumen GI and Reflections feedback thread](https://forums.unrealengine.com/t/lumen-gi-and-reflections-feedback-thread/501108/2142):
>
> Just wanted to follow up that the cvar does not appear to have made it into 5.5.1 or 5.5.2

Appears the cvar didn’t make it into 5.5.2 either

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<div class="post-metadata">

**Author:** ![Uno1982](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/uno1982/32/982436_2.png) [@Uno1982](https://forums.unrealengine.com/u/Uno1982)\
**Post date:** [January 28, 2025, 7:33pm UTC](https://forums.unrealengine.com/t/lumen-no-longer-working-in-ue5-5-dx11-sm5/2126402/13 "2025-01-28T19:33:10Z")

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Workaround for SWRT Lumen in SM5 cheaper than DX12

[![](https://d3kjluh73b9h9o.cloudfront.net/original/4X/b/f/e/bfe5c30de6118353bf64669a98c11233bfe8f1a6.jpeg "UE5.5.2 - Lumen no longer working in DX11 (SM5) [Workaround]") ](https://www.youtube.com/watch?v=bDRdO4k6fKY)

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<div class="post-metadata">

**Author:** ![qhutaozz](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@qhutaozz](https://forums.unrealengine.com/u/qhutaozz)\
**Post date:** [February 7, 2025, 6:33am UTC](https://forums.unrealengine.com/t/lumen-no-longer-working-in-ue5-5-dx11-sm5/2126402/14 "2025-02-07T06:33:28Z")

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I’ve modified `RenderUtils.cpp` then it works in editor. But I’m not sure if it works in packaged version and whether there would be any other problems.

```cpp
bool DoesPlatformSupportLumenGI(EShaderPlatform Platform, bool bSkipProjectCheck)
{
	static IConsoleVariable* CVar = IConsoleManager::Get().FindConsoleVariable(TEXT("r.Lumen.Supported"));
	const bool bLumenSupported = CVar->GetInt() != 0;

	EShaderPlatform ParentPreviewPlatform = SP_NumPlatforms;
	#if WITH_EDITOR
	if (GIsEditor)
	{
		if (FDataDrivenShaderPlatformInfo::GetIsPreviewPlatform(Platform))
		{
			ParentPreviewPlatform = FDataDrivenShaderPlatformInfo::GetPreviewShaderPlatformParent(Platform);
		}
	}
	#endif // WITH_EDITOR

	const bool bMetalSM5 = Platform == SP_METAL_SM5 || ParentPreviewPlatform == SP_METAL_SM5;
	// TODO: fix begin, for DX11 support lumen
	const bool bPCD3DSM5 = Platform == SP_PCD3D_SM5 || ParentPreviewPlatform == SP_PCD3D_SM5;
	const bool bVulkanSM5 = Platform == SP_VULKAN_SM5 || Platform == SP_VULKAN_SM5_ANDROID || ParentPreviewPlatform == SP_VULKAN_SM5 || ParentPreviewPlatform == SP_VULKAN_SM5_ANDROID;
	return (bSkipProjectCheck || bLumenSupported)
		&& FDataDrivenShaderPlatformInfo::GetSupportsLumenGI(Platform)
		&& (IsFeatureLevelSupported(Platform, ERHIFeatureLevel::SM6) || bPCD3DSM5 || bVulkanSM5 || bMetalSM5) // Android and Mac can't rely on SM6 yet, but want to run Lumen
		&& !IsForwardShadingEnabled(Platform);
	// TODO: fix end
}

```

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<div class="post-metadata">

**Author:** ![Uno1982](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/uno1982/32/982436_2.png) [@Uno1982](https://forums.unrealengine.com/u/Uno1982)\
**Post date:** [February 11, 2025, 5:05pm UTC](https://forums.unrealengine.com/t/lumen-no-longer-working-in-ue5-5-dx11-sm5/2126402/15 "2025-02-11T17:05:40Z")

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> [@qhutaozz](#):
>
> ```auto
> // TODO: fix begin, for DX11 support lumen
> const bool bPCD3DSM5 = Platform == SP_PCD3D_SM5 || ParentPreviewPlatform == SP_PCD3D_SM5;
> 
> ```

Thanks for this. I’ll do some testing as well… Looks like a solid fix and I’d approve if you opened a PR against main.

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<div class="post-metadata">

**Author:** ![Uno1982](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/uno1982/32/982436_2.png) [@Uno1982](https://forums.unrealengine.com/u/Uno1982)\
**Post date:** [February 11, 2025, 5:49pm UTC](https://forums.unrealengine.com/t/lumen-no-longer-working-in-ue5-5-dx11-sm5/2126402/16 "2025-02-11T17:49:26Z")

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Also there is now a PR in dev-5.5  
[Restore DX11 SM5 SWRT Lumen by uno1982 · Pull Request #12860 · EpicGames/UnrealEngine](https://github.com/EpicGames/UnrealEngine/pull/12860)

[![](https://d3kjluh73b9h9o.cloudfront.net/original/4X/d/b/d/dbdbe91fa37645b490677d3fd59766faab5d009d.jpeg "UE5.5.3 - Fix DX11 Lumen SWRT & Dual RHI Shader packaging.") ](https://www.youtube.com/watch?v=W9tmPdWA3Ww)

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<div class="post-metadata">

**Author:** ![Vyznawca](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Vyznawca](https://forums.unrealengine.com/u/Vyznawca)\
**Post date:** [March 13, 2025, 7:59am UTC](https://forums.unrealengine.com/t/lumen-no-longer-working-in-ue5-5-dx11-sm5/2126402/17 "2025-03-13T07:59:55Z")

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PR was declined 😕

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<div class="post-metadata">

**Author:** ![Uno1982](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/uno1982/32/982436_2.png) [@Uno1982](https://forums.unrealengine.com/u/Uno1982)\
**Post date:** [March 14, 2025, 4:57am UTC](https://forums.unrealengine.com/t/lumen-no-longer-working-in-ue5-5-dx11-sm5/2126402/18 "2025-03-14T04:57:04Z")

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Yeah I saw however I was informed the cvar is read only and can’t be applied at runtime and should be in the engine ini. I’ll update everyone soon after some testing 👍🏼

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<div class="post-metadata">

**Author:** ![RandomDeveloper9](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@RandomDeveloper9](https://forums.unrealengine.com/u/RandomDeveloper9)\
**Post date:** [March 18, 2025, 10:19am UTC](https://forums.unrealengine.com/t/lumen-no-longer-working-in-ue5-5-dx11-sm5/2126402/19 "2025-03-18T10:19:17Z")

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For me, the Cvar does not work if I simply enter it in the DefaultEngine.INI. So from my tests, I can’t enable Lumen with DX11 and SM5 in 5.5.4

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<div class="post-metadata">

**Author:** ![AJ\_Graphix](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/aj_graphix/32/1194669_2.png) [@AJ\_Graphix](https://forums.unrealengine.com/u/AJ_Graphix)\
**Post date:** [March 19, 2025, 7:13pm UTC](https://forums.unrealengine.com/t/lumen-no-longer-working-in-ue5-5-dx11-sm5/2126402/20 "2025-03-19T19:13:25Z")

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This is sad to see. I hope the removal of Lumen in DX11 is not permanent.

[Next page](https://forums.unrealengine.com/t/lumen-no-longer-working-in-ue5-5-dx11-sm5/2126402.md?page=2)