# \#Ray-Tracing **URL:** https://forums.unrealengine.com/tag/ray-tracing/2545.md [Latest](https://forums.unrealengine.com/latest.md) · [Categories](https://forums.unrealengine.com/categories.md) · [Tags](https://forums.unrealengine.com/tags.md) --- ## [Ray Traced shadows make reflections on SLW pass through objects](https://forums.unrealengine.com/t/ray-traced-shadows-make-reflections-on-slw-pass-through-objects/2853358)
**Author:** [@Miguel1900](https://forums.unrealengine.com/u/Miguel1900)\ **Replies:** 0\ **Last updated:** [November 10, 2026, 2:24pm UTC](https://forums.unrealengine.com/t/ray-traced-shadows-make-reflections-on-slw-pass-through-objects/2853358 "2026-11-10T14:24:33Z")
Summary If you enable Ray Traced shadows, lights won’t be occluded by objects placed between them and a Single Layer Water material. I already reported this bug years ago, and also many other users. It seems that Epic d… --- ## [\[UE 5.8.3\]\[Lumen\] Broad interior light leakage in a sealed stock-cube room with Screen Probe Gather](https://forums.unrealengine.com/t/ue-5-8-3-lumen-broad-interior-light-leakage-in-a-sealed-stock-cube-room-with-screen-probe-gather/2839515)
**Author:** [@SilentGarud](https://forums.unrealengine.com/u/SilentGarud)\ **Replies:** 0\ **Last updated:** [October 11, 2026, 2:51pm UTC](https://forums.unrealengine.com/t/ue-5-8-3-lumen-broad-interior-light-leakage-in-a-sealed-stock-cube-room-with-screen-probe-gather/2839515 "2026-10-11T14:51:48Z")
Summary I reproduced broad interior wall illumination in a fresh Blank Blueprint project using six overlapping opaque stock Cube meshes and one exterior Directional Light. The closed room has no skylight, atmosphere, fog… --- ## [UE5.7 Uses LOD 1 for RT shadows instead of LOD 0, how to fix?](https://forums.unrealengine.com/t/ue5-7-uses-lod-1-for-rt-shadows-instead-of-lod-0-how-to-fix/2721127)
**Author:** [@Naiuma](https://forums.unrealengine.com/u/Naiuma)\ **Replies:** 0\ **Last updated:** [May 10, 2026, 8:56am UTC](https://forums.unrealengine.com/t/ue5-7-uses-lod-1-for-rt-shadows-instead-of-lod-0-how-to-fix/2721127 "2026-05-10T08:56:48Z")
Hello guys, UE5.7 Uses LOD1 for RT shadows instead of LOD0, do you know how to fix? Sometimes deleting the DerivedDataCache folder helps but only temporarily. r.RayTracing.Shadows 0 helps but I would prefer to have it e… --- ## [\[Bug\] Render thread freeze in RayTracing\_FinishGatherInstances - lost task wakeup with 50+ players (UE 5.7.4) ](https://forums.unrealengine.com/t/bug-render-thread-freeze-in-raytracing-finishgatherinstances-lost-task-wakeup-with-50-players-ue-5-7-4/2709809)
**Author:** [@Mouloud95](https://forums.unrealengine.com/u/Mouloud95)\ **Replies:** 0\ **Last updated:** [March 29, 2026, 1:05pm UTC](https://forums.unrealengine.com/t/bug-render-thread-freeze-in-raytracing-finishgatherinstances-lost-task-wakeup-with-50-players-ue-5-7-4/2709809 "2026-03-29T13:05:54Z")
Summary Summary Random render thread freeze (4+ seconds) in multiplayer with 50+ skeletal mesh characters and Hardware Ray Tracing enabled (Lumen HW RT, MegaLights, Nanite, DX12). Details The render thread hangs at Fin… --- ## [Metallic value shown in Ray Tracing Debug visualization appears gamma corrected compared to the actual input value ](https://forums.unrealengine.com/t/metallic-value-shown-in-ray-tracing-debug-visualization-appears-gamma-corrected-compared-to-the-actual-input-value/2704773)
**Author:** [@JackChang0226](https://forums.unrealengine.com/u/JackChang0226)\ **Replies:** 0\ **Last updated:** [March 9, 2026, 2:03pm UTC](https://forums.unrealengine.com/t/metallic-value-shown-in-ray-tracing-debug-visualization-appears-gamma-corrected-compared-to-the-actual-input-value/2704773 "2026-03-09T14:03:18Z")
Hi, I noticed something confusing while inspecting material parameters using the Ray Tracing Debug visualization in Unreal Engine 5.5.4. To reproduce the issue, I created a very simple scene: Two spheres Both sph… --- ## [Unreal 5.7 RayTracing Crash](https://forums.unrealengine.com/t/unreal-5-7-raytracing-crash/2680260)
**Author:** [@Kye1002](https://forums.unrealengine.com/u/Kye1002)\ **Replies:** 11\ **Last updated:** [February 19, 2026, 11:41am UTC](https://forums.unrealengine.com/t/unreal-5-7-raytracing-crash/2680260 "2026-02-19T11:41:14Z")
Hi everyone, I’m running into a consistent crash in Unreal Engine 5.7 and I’m having trouble figuring out the exact cause. I’m hoping someone who has dealt with this before can point me in the right direction. This is … --- ## [Rect Light Reflections in RayTraced Translucency](https://forums.unrealengine.com/t/rect-light-reflections-in-raytraced-translucency/2698703)
**Author:** [@Data\_Vision](https://forums.unrealengine.com/u/Data_Vision)\ **Replies:** 0\ **Last updated:** [February 10, 2026, 10:02am UTC](https://forums.unrealengine.com/t/rect-light-reflections-in-raytraced-translucency/2698703 "2026-02-10T10:02:35Z")
Hello ! I’ve found a troubling issue : I use a lot of rect lights reflecting in translucent meshes (windshields etc), and i get some culling/clipping of the reflections. Here we can see three spheres, from left to righ… --- ## [Lighting Cinematic Tool 1.0 - Official Release (Free for 2 Weeks)](https://forums.unrealengine.com/t/lighting-cinematic-tool-1-0-official-release-free-for-2-weeks/2698494)
**Author:** [@Argentum\_Studio](https://forums.unrealengine.com/u/Argentum_Studio)\ **Replies:** 2\ **Last updated:** [February 9, 2026, 2:33pm UTC](https://forums.unrealengine.com/t/lighting-cinematic-tool-1-0-official-release-free-for-2-weeks/2698494 "2026-02-09T14:33:14Z")
Lighting Cinematic Tool 1.0 - Official Release (Free for 2 Weeks) Hi everyone, we’re happy to share the release of our new tool for Unreal Engine cinematics - Lighting Cinematic Tool. FAB Release UE5.5+ Lighting Cinem… --- ## [Nothing that I do solves the IDIOTIC Reflection Problem](https://forums.unrealengine.com/t/nothing-that-i-do-solves-the-idiotic-reflection-problem/2697070)
**Author:** [@malik\_217](https://forums.unrealengine.com/u/malik_217)\ **Replies:** 19\ **Last updated:** [February 5, 2026, 7:17am UTC](https://forums.unrealengine.com/t/nothing-that-i-do-solves-the-idiotic-reflection-problem/2697070 "2026-02-05T07:17:39Z")
I’m using unreal engine 5.6 and have been having this issues since 5.4. The reflections are just not accurate at distance not in raster not raytracing, even with all the settings at high everything turned ONN for ray tra… --- ## [Ray-Traced Shadows on Nanite Skeletal Meshes: Shadows Appear to Ignore Displacement - Bug or Limitation? ](https://forums.unrealengine.com/t/ray-traced-shadows-on-nanite-skeletal-meshes-shadows-appear-to-ignore-displacement-bug-or-limitation/2352546)
**Author:** [@ShiinaE](https://forums.unrealengine.com/u/ShiinaE)\ **Replies:** 3\ **Last updated:** [January 31, 2026, 6:55pm UTC](https://forums.unrealengine.com/t/ray-traced-shadows-on-nanite-skeletal-meshes-shadows-appear-to-ignore-displacement-bug-or-limitation/2352546 "2026-01-31T18:55:19Z")
Hi everyone, I’ve been working with ray-traced shadows on Nanite skeletal meshes and noticed something unusual. It seems like the shadows are being calculated based on the mesh’s original geometry before displacement is… --- ## [AMD GPUs artifacts Ray Tracing Lumen](https://forums.unrealengine.com/t/amd-gpus-artifacts-ray-tracing-lumen/815952)
**Author:** [@oOmanhattanOo](https://forums.unrealengine.com/u/oOmanhattanOo)\ **Replies:** 1\ **Last updated:** [December 4, 2025, 5:35am UTC](https://forums.unrealengine.com/t/amd-gpus-artifacts-ray-tracing-lumen/815952 "2025-12-04T05:35:18Z")
Hello dear community, I know that some of you have already complained about the visual bugs of AMD GPUs starting from version 5.1. I also want to express my frustration now. I can understand that not everything works as… --- ## [Nanite Geometry Collections don't cast shadow in Hardware Ray Tracing](https://forums.unrealengine.com/t/nanite-geometry-collections-dont-cast-shadow-in-hardware-ray-tracing/1845680)
**Author:** [@Danta1ion](https://forums.unrealengine.com/u/Danta1ion)\ **Replies:** 4\ **Last updated:** [November 23, 2025, 1:46pm UTC](https://forums.unrealengine.com/t/nanite-geometry-collections-dont-cast-shadow-in-hardware-ray-tracing/1845680 "2025-11-23T13:46:28Z")
As described in the above image, when I enabled both hardware ray-traced shadow and nanite geometry collection, the shadow disappeared. The nanite geometry only accepts direct lighting from sunlight and point light, w… --- ## [How to get the scene Accelerate Structure (TLAS) for custom Ray Tracing](https://forums.unrealengine.com/t/how-to-get-the-scene-accelerate-structure-tlas-for-custom-ray-tracing/696723)
**Author:** [@FluffyBunnyO](https://forums.unrealengine.com/u/FluffyBunnyO)\ **Replies:** 7\ **Last updated:** [November 17, 2025, 3:53pm UTC](https://forums.unrealengine.com/t/how-to-get-the-scene-accelerate-structure-tlas-for-custom-ray-tracing/696723 "2025-11-17T15:53:08Z")
I want to cast custom rays in order to compute something specific. I will be casting 1 ray per texture pixel, probably 1024X1024. I’ve set up everything I need in order to do so; shader, parameters, buffers, render thre… --- ## [DLSS Ray Reconstruction crashes editor](https://forums.unrealengine.com/t/dlss-ray-reconstruction-crashes-editor/2667132)
**Author:** [@OneNot](https://forums.unrealengine.com/u/OneNot)\ **Replies:** 1\ **Last updated:** [October 21, 2025, 2:26pm UTC](https://forums.unrealengine.com/t/dlss-ray-reconstruction-crashes-editor/2667132 "2025-10-21T14:26:40Z")
After updating my project to 5.6, it started crashing. I quickly found that the issue was Ray Reconstruction. I disabled it and the problem immediately went away. (Still using DLSS-SR and NIS sharpening). Now, sometime … --- ## [Raytracing . Landscape does not appear correctly in ray traced reflections.](https://forums.unrealengine.com/t/raytracing-landscape-does-not-appear-correctly-in-ray-traced-reflections/2658060)
**Author:** [@kurylo3d](https://forums.unrealengine.com/u/kurylo3d)\ **Replies:** 0\ **Last updated:** [September 19, 2025, 12:13am UTC](https://forums.unrealengine.com/t/raytracing-landscape-does-not-appear-correctly-in-ray-traced-reflections/2658060 "2025-09-19T00:13:00Z")
Landscape does not appear correct in ray traced reflections.. thats basically just a tiling grass material that i got from brushify. Am i doing somethign wrong? Thoughts or approaches to make this better? --- ## [Parallel Raycast for Lidar simulation](https://forums.unrealengine.com/t/parallel-raycast-for-lidar-simulation/612158)
**Author:** [@Fractal\_Tree](https://forums.unrealengine.com/u/Fractal_Tree)\ **Replies:** 8\ **Last updated:** [September 8, 2025, 1:38pm UTC](https://forums.unrealengine.com/t/parallel-raycast-for-lidar-simulation/612158 "2025-09-08T13:38:30Z")
Hello there, I’m trying to explore the capabilities of Unreal Engine 5 for robotics simulation, and I’m starting to hit quite a wall with regard to the simulation of a Lidar sensor. My naïve implementation simply consi… --- ## [Nanite geometry completely broken (check images), but works fine in Editor mode](https://forums.unrealengine.com/t/nanite-geometry-completely-broken-check-images-but-works-fine-in-editor-mode/2632485)
**Author:** [@vidhanthb](https://forums.unrealengine.com/u/vidhanthb)\ **Replies:** 2\ **Last updated:** [August 27, 2025, 4:09am UTC](https://forums.unrealengine.com/t/nanite-geometry-completely-broken-check-images-but-works-fine-in-editor-mode/2632485 "2025-08-27T04:09:37Z")
Hi, I’ve been facing a very weird issue and I have googled a lot and not yet found a solution. As you can see in the image, when nanite is enabled for my mesh it’s completely broken, but looks fine in the Editor mode. W… --- ## [Height Fog invisible in Ray Traced Reflections.](https://forums.unrealengine.com/t/height-fog-invisible-in-ray-traced-reflections/1895517)
**Author:** [@Online\_Learner\_KPoqc](https://forums.unrealengine.com/u/Online_Learner_KPoqc)\ **Replies:** 3\ **Last updated:** [August 9, 2025, 9:49pm UTC](https://forums.unrealengine.com/t/height-fog-invisible-in-ray-traced-reflections/1895517 "2025-08-09T21:49:11Z")
I’m using Raytracing with a simple glass material. For some reason, the fog doesn’t show up in the glass reflection. I tried using \ but it doesn’t affect the scene. Can someone plea… --- ## [Ray Tracing, Noisy gameplay. How to fix](https://forums.unrealengine.com/t/ray-tracing-noisy-gameplay-how-to-fix/2618962)
**Author:** [@SCARBLAZ1](https://forums.unrealengine.com/u/SCARBLAZ1)\ **Replies:** 0\ **Last updated:** [July 26, 2025, 11:45am UTC](https://forums.unrealengine.com/t/ray-tracing-noisy-gameplay-how-to-fix/2618962 "2025-07-26T11:45:25Z")
Things I have tried: Increasing Ray Tracing rays Denoise ( True By default in Post process volume ) Removing Motion Blur Not just when moving, when stationery as well the floor, vehicle looks noisy. --- ## [Hardware Ray Tracing Settings](https://forums.unrealengine.com/t/hardware-ray-tracing-settings/2566747)
**Author:** [@X-perto](https://forums.unrealengine.com/u/X-perto)\ **Replies:** 3\ **Last updated:** [June 20, 2025, 10:02am UTC](https://forums.unrealengine.com/t/hardware-ray-tracing-settings/2566747 "2025-06-20T10:02:30Z")
Anyone familiar with these settings related to HW raytracing? If they supposedly increase performance then why are they not enabled by default? --- ## [Post process volume translucency ray tracing issue](https://forums.unrealengine.com/t/post-process-volume-translucency-ray-tracing-issue/2566537)
**Author:** [@PuChiNg](https://forums.unrealengine.com/u/PuChiNg)\ **Replies:** 0\ **Last updated:** [June 19, 2025, 6:18pm UTC](https://forums.unrealengine.com/t/post-process-volume-translucency-ray-tracing-issue/2566537 "2025-06-19T18:18:32Z")
Hi there, i’m having an issue with ray tracing translucency on glass material, it’s the common automotive glass material As you can see enabling ray tracing creates an opaque-like reflection of the skylight or hdri w… --- ## [Lumen Far Field problems](https://forums.unrealengine.com/t/lumen-far-field-problems/2555228)
**Author:** [@Pete\_the\_B](https://forums.unrealengine.com/u/Pete_the_B)\ **Replies:** 0\ **Last updated:** [June 13, 2025, 4:55pm UTC](https://forums.unrealengine.com/t/lumen-far-field-problems/2555228 "2025-06-13T16:55:03Z")
Hi, has anyone had success getting Lumen Far Field to work? I only get random black artifacts on screen and everything glows in rainbow colors after setting r.LumenScene.FarField to 1. --- ## [Repeated crashes linked to RayTracing ?](https://forums.unrealengine.com/t/repeated-crashes-linked-to-raytracing/2516519)
**Author:** [@Data\_Vision](https://forums.unrealengine.com/u/Data_Vision)\ **Replies:** 0\ **Last updated:** [May 18, 2025, 12:58pm UTC](https://forums.unrealengine.com/t/repeated-crashes-linked-to-raytracing/2516519 "2025-05-18T12:58:55Z")
Hi, i’ve been having lots of crashes in my recent cinematic project, linked to ray tracing. Sometimes i get handled ensures messages, and sometimes it just crashes. Rendering via MRQ sometimes fails, and almost always f… --- ## [Raytracing Reflections are not looking accurate](https://forums.unrealengine.com/t/raytracing-reflections-are-not-looking-accurate/2511041)
**Author:** [@malik\_217](https://forums.unrealengine.com/u/malik_217)\ **Replies:** 0\ **Last updated:** [May 15, 2025, 7:42am UTC](https://forums.unrealengine.com/t/raytracing-reflections-are-not-looking-accurate/2511041 "2025-05-15T07:42:45Z")
The reflections on my glass does not seem accurate, even though my translucency is set to Raytracing as you can see in the Images below. Mirror doesn’t reflect another mirrors reflection and blueish reflection, seems li… --- ## [How To Fix Jagged Shadows?](https://forums.unrealengine.com/t/how-to-fix-jagged-shadows/481582)
**Author:** [@Stevenw9](https://forums.unrealengine.com/u/Stevenw9)\ **Replies:** 7\ **Last updated:** [February 4, 2024, 8:49pm UTC](https://forums.unrealengine.com/t/how-to-fix-jagged-shadows/481582 "2024-02-04T20:49:19Z")
Problem: The point-of-origin on shadows produces a sharp, jagged edge. Screenshot: Detailed Explanation: I have tried to figure this out on my own, but days of searching and experimenting has yielded me zero results… --- ## [Can 3d translucent widgets be seen with ray tracing?](https://forums.unrealengine.com/t/can-3d-translucent-widgets-be-seen-with-ray-tracing/477701)
**Author:** [@Rivenris](https://forums.unrealengine.com/u/Rivenris)\ **Replies:** 2\ **Last updated:** [April 25, 2025, 6:22am UTC](https://forums.unrealengine.com/t/can-3d-translucent-widgets-be-seen-with-ray-tracing/477701 "2025-04-25T06:22:35Z")
I am trying to use a widget component with translucency. When I use Raster translucency for rendering, I get the desired effect, a see through UMG widget component: However, When I switch to Ray Traced Translucency, t… --- ## [Lumen broken ingame / Hardware Ray-Tracing option is not working](https://forums.unrealengine.com/t/lumen-broken-ingame-hardware-ray-tracing-option-is-not-working/2390417)
**Author:** [@TRIVIAL\_G](https://forums.unrealengine.com/u/TRIVIAL_G)\ **Replies:** 1\ **Last updated:** [March 20, 2025, 1:26pm UTC](https://forums.unrealengine.com/t/lumen-broken-ingame-hardware-ray-tracing-option-is-not-working/2390417 "2025-03-20T13:26:57Z")
Summary the Hardware Ray-Tracing option has no longer any effect on PC. Even if you toggle the option on or off (the getaway update). Lumen global illumination settings are changed from the editor scalability to the PC g… --- ## [Are there any articles or videos about Ray Tracing View Mode?](https://forums.unrealengine.com/t/are-there-any-articles-or-videos-about-ray-tracing-view-mode/2389131)
**Author:** [@tancen](https://forums.unrealengine.com/u/tancen)\ **Replies:** 4\ **Last updated:** [March 19, 2025, 9:20am UTC](https://forums.unrealengine.com/t/are-there-any-articles-or-videos-about-ray-tracing-view-mode/2389131 "2025-03-19T09:20:06Z")
Through the Stat SceneRendering command, I located Finish Gather Ray Tracing Instances, which took a lot of Draw Time in my level, and then I changed the View Mode to Ray Tracing Debug - Instances, after which my screen … --- ## [City Sample Vehicles shadow glitch when Shadow Raytracing is activated.](https://forums.unrealengine.com/t/city-sample-vehicles-shadow-glitch-when-shadow-raytracing-is-activated/2390303)
**Author:** [@ObamaWithHair](https://forums.unrealengine.com/u/ObamaWithHair)\ **Replies:** 0\ **Last updated:** [March 14, 2025, 9:23pm UTC](https://forums.unrealengine.com/t/city-sample-vehicles-shadow-glitch-when-shadow-raytracing-is-activated/2390303 "2025-03-14T21:23:38Z")
if i remove raytrace shadows its alright but can i somehow jsut turn off raytacing for this material/mesh? or is there another solution? im on unreal 5.4 and this is city sample vehicles. --- ## [Compacted acceleration structure size is expected to be non-zero. This error suggests that GPU readback synchronization is broken.](https://forums.unrealengine.com/t/compacted-acceleration-structure-size-is-expected-to-be-non-zero-this-error-suggests-that-gpu-readback-synchronization-is-broken/2349423)
**Author:** [@GreenHowitzer](https://forums.unrealengine.com/u/GreenHowitzer)\ **Replies:** 3\ **Last updated:** [February 24, 2025, 7:48pm UTC](https://forums.unrealengine.com/t/compacted-acceleration-structure-size-is-expected-to-be-non-zero-this-error-suggests-that-gpu-readback-synchronization-is-broken/2349423 "2025-02-24T19:48:32Z")
I really much require assistance with solving this once and for all now that I require Ray tracing to be enabled for megalights I cannot any longer have this bug as our project requires HW RT now for megalights. AMD 660… [Next page](https://forums.unrealengine.com/tag/ray-tracing/2545.md?match_all_tags=true&page=1&tags%5B%5D=Ray-Tracing)