# UE5.7 - Fix: Lumen not working for SM5 DX11 and DX12 **URL:** \ **Category:** Rendering\ **Tags:** directx, unreal-engine, Lumen, Shaders\ **Created:** [November 18, 2025, 5:20am UTC](https://forums.unrealengine.com/t/ue5-7-fix-lumen-not-working-for-sm5-dx11-and-dx12/2676047 "2025-11-18T05:20:56Z")\ **Posts on this page:** 5\ **Page:** 1
**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 18, 2025, 5:20am UTC](https://forums.unrealengine.com/t/ue5-7-fix-lumen-not-working-for-sm5-dx11-and-dx12/2676047/1 "2025-11-18T05:20:56Z")
When using the cvar r.Lumen.Supported.SM5=1 which was working fine in 5.6 … UE5.7 presents with the following in DX11 and DX12 SM5 ![image](https://d3kjluh73b9h9o.cloudfront.net/original/4X/a/4/1/a41dd396d5e70cb9812336508f27dbd824047c98.png) [https://github.com/uno1982/UnrealEngine/tree/5.7-Lumen-D3D-SM5-Fix](https://github.com/uno1982/UnrealEngine/tree/5.7-Lumen-D3D-SM5-Fix) Fix: Restore Lumen support for D3D Shader Model 5 (DX11/DX12 SM5) Unreal Engine 5.7 broke Lumen on D3D SM5 due to StochasticLighting shader requiring 8 UAVs (hardware limit: 4 UAVs). This commit restores full Lumen functionality with a fallback path that combines UE 5.6’s simpler approach with 5.7’s compatibility requirements. Key Changes: - StochasticLighting.cpp: D3D SM5 detection, simplified 2-UAV depth/normal copy - Created LumenTileBitmask with all tiles marked (0xFF) for 5.7 compatibility - LumenScreenProbeGather.cpp: Fixed GI temporal validation (check data not pointer) - LumenReflectionDenoiserTemporal.usf: Conditional depth read for D3D SM5 - New shader: StochasticLightingDenoising.usf (5.6-style history storage) Result: ✅ Full Lumen GI + Reflections working on DX11 and DX12 SM5 ✅ DX11 SM5 with Lumen SWRT is fastest performing Lumen path ✅ Quality identical to SM6+, no tile culling optimization ✅ Production ready, tested across multiple scenarios Files Modified: - StochasticLighting.cpp (fallback path + LumenTileBitmask creation) - LumenScreenProbeGather.cpp (temporal validation fix) - LumenReflections.cpp (D3D SM5 comment) - LumenReflectionDenoiserTemporal.usf (depth consistency) - LumenScreenProbeGatherTemporal.usf (PackedPixelData validation) - StochasticLightingDenoising.usf (new 5.6-style shader) - DeferredShadingRenderer.h (function declaration) - LUMEN\_D3D\_SM5\_FIX\_SUMMARY.md (comprehensive documentation) ![](https://d3kjluh73b9h9o.cloudfront.net/optimized/4X/9/9/8/998eb5de49db231725962ba96d5c904badfda78f_2_690x388.jpeg)https://www.youtube.com/embed/UZDPzSjCskc?feature=oembed&wmode=opaque ---
**Author:** ![kalkulator777](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@kalkulator777](https://forums.unrealengine.com/u/kalkulator777)\ **Post date:** [November 19, 2025, 1:28am UTC](https://forums.unrealengine.com/t/ue5-7-fix-lumen-not-working-for-sm5-dx11-and-dx12/2676047/2 "2025-11-19T01:28:30Z")
Amazing work, thanks! ---
**Author:** ![NailGUNNERX](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@NailGUNNERX](https://forums.unrealengine.com/u/NailGUNNERX)\ **Post date:** [December 25, 2025, 4:25pm UTC](https://forums.unrealengine.com/t/ue5-7-fix-lumen-not-working-for-sm5-dx11-and-dx12/2676047/3 "2025-12-25T16:25:45Z")
Hello [@Uno1982](https://dev.epicgames.com/community/api/user_profiles/tab-redirect/about?discourse_username=Uno1982), Firstly, thank you for the fix! Here is a small bug report: There are shadow artifacts only in High Global illumination scalibility settings. While moving in a real scene, some places are extra dark but with a very big pattern and the pattern is moving. Place some huge rectangular cubes like skyscraper, then you can see them. By default r.Lumen.ScreenProbeGather.ShortRangeAO.BentNormal=0 on High When I use r.Lumen.ScreenProbeGather.ShortRangeAO.BentNormal=1 on High shadow artifacts are gone but it probably cost extra on GPU Those artifacts does not exist when using DX12, SM6 ---
**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 29, 2025, 9:51pm UTC](https://forums.unrealengine.com/t/ue5-7-fix-lumen-not-working-for-sm5-dx11-and-dx12/2676047/4 "2025-12-29T21:51:04Z")
I’ve bumped the branch to 5.7.1 and included some fixes .. thanks for the headsup! Please let me know if your issues remain. [![](https://d3kjluh73b9h9o.cloudfront.net/original/4X/9/9/8/998eb5de49db231725962ba96d5c904badfda78f.jpeg "UE5.7.1 - DX 11 & DX12 (SM5) Lumen Fix!") ](https://www.youtube.com/watch?v=zo6aNKgw8ik) ---
**Author:** ![Ken.Brueck](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Ken.Brueck](https://forums.unrealengine.com/u/Ken.Brueck)\ **Post date:** [September 4, 2026, 4:24pm UTC](https://forums.unrealengine.com/t/ue5-7-fix-lumen-not-working-for-sm5-dx11-and-dx12/2676047/5 "2026-09-04T16:24:22Z")
@Uno1982 Great work on 5.7.1! Any chance you’re looking to do the same for 5.8.2?