Niagara GPU particles stutter when main viewport is not rendering

this seemed to work on UE4.27. In UE5.03, niagara gpu particles stutter (like 1-3 updates/sec) when viewed via scene capture, when the main viewport is not rendered.

to reproduce:

  • one niagara system with CPU sim for reference
  • one niagara system with GPU sim
  • create render target
  • create actor with SceneCaptue2D component and give it the render target
  • create a UMG widget to show the render target via ImageWidget
  • disable viewport by calling “UGameplayStatics::SetEnableWorldRendering(WorldContext, false);”

now the GPU particles should stutter, while the CPU particles don’t. reenabling the world rendering fixes it again as does setting the GPU sim to CPU.

anybody know a way to fix this? or why it happens exactly?