Shader Stutter Fix - Enable UE Shader Cache Defaults

For some reason, the developers of this game decided to mess with the UE shader cache values. This causes the shaders to load synchronous on the main thread instead of asynchronous and using multithreaded.

I have no idea why they did this, but anyway.

You don't have to download the Engine.ini file, just paste this into the file

r. Shaders. Optimize=1

r. ShaderPipelineCache. StartupMode=3 ;custom

r. ShaderPipelineCache. Enabled=1

r. ShaderPipelineCache. ReportPSO=1

r. ShaderPipelineCache. GameFileMaskEnabled=0

r. ShaderPipelineCache. LazyLoadShadersWhenPSOCacheIsPresent=1 ; custom

r. ShaderPipelineCache. BatchSize=50

r. ShaderPipelineCache. BatchTime=16

r. PSOPrecache. Validation=0 ; custom

r.pso. PrecompileThreadPoolPercentOfHardwareThreads=75

r.pso.evictiontime=60

Just remember to set Engine.ini to read-only because the game will reset it if you don't

The one that are marked with ; custom are my modifications which should probably be enabled anyway.

The biggest change, in my opinion, is r.pso. PrecompileThreadPoolPercentOfHardwareThreads. To explain what this option does, from the Unreal documentation:

By default, Unreal Engine uses a PSO precaching thread pool to compile the PSO asynchronously. If r.pso. PrecompileThreadPoolSize or r.pso. PrecompileThreadPoolPercentOfHardwareThreads

is set, then the thread pool will be used. Otherwise, PSO compilation falls back to using regular background tasks, which are scheduled with the rest of the engine's workloads.

And r.pso. PrecompileThreadPoolPercentOfHardwareThreads does the following:

Sets the thread pool size to be a percentage of available hardware threads and creates a thread pool with that size. The default size is 75, which represents 75% of hardware threads.

https://dev.epicgames.com/documentation/en-us/unreal-engine/pso-precaching-for-unreal-engine

The devs had this set to 0. That means, as the documentation says, all shader cache related actions during the game would have the same low, default priority as everything else. It's quite obvious why the game stutters.

To be fair, the documentation also states:

Additional Notes:

[]With an unbounded amount of max threads in the thread pool it might be possible to run out of system memory while compiling PSOs on systems with a lot of processors but not a lot of memory. Each thread compiling PSOs can use up to 2 Gbs of memory, so limiting this amount might make sense for your project.

[]During gameplay, 75 percent of hardware threads might be a lot. Contention with regular foreground threads might be noticeable causing mi