Summary
Our packaged application crashes on Linux with the official, unpatched UE 5.8.4 engine when using Vulkan and -RenderOffscreen.
The application uses Pixel Streaming and Cesium terrain. Repeatedly scrolling the mouse wheel to move the camera from low altitude toward a wider view of the globe frequently triggers the failure.
The issue was first observed after upgrading from UE 5.6 to UE 5.8. In earlier diagnostic tests, removing -RenderOffscreen avoided the crash, and limiting the frame rate to 30 FPS also prevented it in some trials. Historical failure captures showed VK_ERROR_DEVICE_LOST and NVIDIA Xid 109 / CTX SWITCH TIMEOUT.
I built and tested a patched UE 5.8.4 Installed Build. The patch adds frame pacing specifically for Linux Vulkan offscreen rendering: it advances submission of the current frame, then waits for the previous frame using existing GPU completion events. The crash was not reproduced in my tests with this build.
A candidate patch is available for review. These results support investigating synchronization in the offscreen path, but do not establish the exact underlying resource-lifetime failure.
What Type of Bug are you experiencing?
Rendering (Graphics / Niagara)
Steps to Reproduce
These steps describe reproduction in our existing application, which uses Pixel Streaming and Cesium terrain. A standalone minimal reproduction project has not yet been prepared.
- Package the application for Linux x86_64 using the official, unpatched UE 5.8.4 engine with Vulkan.
- Launch it with -RenderOffscreen and the application’s required Pixel Streaming and control-service arguments. Use an uncapped frame rate.
- Connect through the Pixel Streaming browser client and enter fullscreen.
- Load the Cesium terrain/ellipsoid scene and position the camera near the surface.
- Repeatedly scroll the mouse wheel to move the camera upward and farther away, increasing the visible area of the globe.
- Continue this camera operation and observe the application for a hang or crash. The time to failure varies.
The camera movement is implemented by our application’s controls; these steps do not imply that an unmodified template project reproduces the issue.
Expected Result
The application continues rendering offscreen and responding to camera input without a GPU hang or process termination while the camera moves from low altitude toward a wider view of the globe.
Observed Result
The application can become unresponsive and crash during repeated camera zoom-out operations. The issue remains reproducible with the official, unpatched UE 5.8.4 engine on Linux.
Earlier diagnostic captures showed VK_ERROR_DEVICE_LOST and NVIDIA Xid 109 / CTX SWITCH TIMEOUT. Those captures predate the current 5.8.4 validation.
After rebuilding UE 5.8.4 with the candidate Linux Vulkan offscreen frame-pacing patch and repackaging the application, the crash was not reproduced in the tests completed so far.
Affects Versions
5.8
Platform(s)
Linux
Additional Notes
Operating system:
- Debian 12
- Gentoo
- Ubuntu 24.04
The issue has been reproduced in the following official, unpatched Unreal Engine versions:
- 5.8.2
- 5.8.3
- 5.8.4
The issue has been observed on both GPU models:
- NVIDIA GeForce RTX 3050 with 8 GB VRAM
- NVIDIA GeForce RTX 5060 Ti with 16 GB VRAM
NVIDIA driver versions tested:
- 595.99.02
- 580.178.04
- 615.78.08
The same offscreen rendering crash was observed with each of these driver versions.
The patched UE 5.8.4 build was tested for more than one hour without reproducing the crash.
Related pull request:
Fix Linux Vulkan offscreen frame pacing — #15361