[Bug/Help] Compiling AMD FSR3 Plugin for Linux on UE 5.6.1 - Cascading Clang & Linker Errors

Development Pipeline & Plugins
1

Hello everyone,

I’m currently attempting to build a native Linux version of my project using a custom source build of Unreal Engine 5.6.1, but I am completely blocked by the AMD FSR3 Plugin.

The C++ source seems heavily biased toward Windows/MSVC, causing Clang to throw multiple errors during the Build.sh process. Consequently, the binaries fail to build, causing the editor to throw a missing module error upon launch.

Has anyone successfully patched or compiled the FSR3 plugin for Linux on 5.6?

Environment:

  • OS: Rocky Linux 8

  • Compiler: Bundled v25_clang-18.1.0-rockylinux8 toolchain

  • Engine: UE 5.6.1 (Source Build)

  • Project: GameAnimationSampleEditor

  • Plugin: Official AMD FSR3 Plugin

The Issues:

1. Windows-Specific String Functions Clang rejects the use of MSVC-specific secure string functions found throughout the SDK (e.g., ffx_fsr3upscaler.cpp).

Plaintext

error: use of undeclared identifier 'wcscpy_s'; did you mean 'wcscpy'?

(Note: Wrapping these in #ifndef _WIN32 clears the immediate error, but reveals deeper issues).

2. Case-Sensitivity in Includes Because Linux is strictly case-sensitive, the build fails on AMD’s internal includes:

C++

#include <FidelityFx/host/ffx_types.h> // Fails: directory is 'FidelityFX'

3. Memory Alignment / Static Assert Failure Linux Clang pads the context struct differently than MSVC, causing this assertion to fail in ffx_frameinterpolation.cpp:

Plaintext

error: static assertion failed due to requirement 'sizeof(FfxFrameInterpolationContext) >= sizeof(FfxFrameInterpolationContext_Private)'

(Evaluates to 524288 >= 768072).

4. Missing UE 5.6 Rendering Headers In FFXFSR3TemporalUpscalerHistory.h, the compiler fails to find a core rendering header.

Plaintext

fatal error: 'TranslucentPassResource.h' file not found

5. Linker Errors (Optical Flow API) For the modules that do manage to compile, they fail at the linker stage:

Plaintext

ld.lld: error: undefined symbol: ffxSafeReleasePipeline
>>> referenced by ffx_opticalflow.cpp

6. Editor Launch Failure (Missing Modules) Because the build fails, the Unreal Editor cannot open the project.

Plaintext

Plugin 'FSR3' failed to load because module 'FFXFSR3Settings' could not be found.

(Note: I suspect this is also because “Linux” is missing from the SupportedTargetPlatforms array in the FSR3.uplugin file, but I cannot test it until the compile errors are resolved).

Questions:

  1. Does anyone have a patched fork of the FSR3 plugin that resolves these Clang/Linux constraints?

  2. What Build.cs modifications are required to fix the missing TranslucentPassResource.h include path for UE 5.6?

Any guidance or workarounds would be hugely appreciated. Thank you!