Weird Mesh Rendering With multiple Niagara Mesh Renderer

Has anybody experienced a glitch similar to this :


[Zip with a video][1]

Here i have a GPU emitter setup as a fountain with multiple mesh renderer and when i spawn a few of them at the same place, some particle spawn with their mesh all messed up.

I did some debugging with RenderDoc and it seems the vertices on some instances of the mesh particles are incorrect in the output of the vertex shader for some reason.

To Reproduce

I couldn’t find a way to reproduce the bug in a consistent manner but here is the simplest setup i had where it did occur:

1. Set a Project in DirectX12

2. Create a new default map

3. Setup a Niagara system with the fountain emitter template. Change for a GPU Emitter and add multiple mesh renderer, each with different RendererVisibility. Set each particle to a random VisibilityTag.

4. Spawn many system at location (0,0,0) either by blueprint in PIE or by copy paste in editor
With enough system overlapping the bug should appear.

Additional info

Although this setup is sufficient to trigger the bug, I found that adding these to the scene make it way more likely to occur

  • Set CastShadow on the niagara systems
    spawned in the world and have one or
    more movable light casting shadow
  • Add one or more SceneCapture
    component (with a render target and
    set to tick every frame)

If you do that, the engine might crash unless you set the Niagara.GPUDrawIndirectArgsBufferSlack to something higher than the default value of 2.

  • Setting Niagara.GPUDrawIndirectArgsBufferSlack=16
    seems enough


  • UE4.26 and 4.27
  • Windows 10
  • Intel Core i9-10900
  • Tested on RTX3080, RTX2070 and QUADRO

Hi man,
think I’ve had a very similar issue with cpu simulated niagara mesh renderers, showing up only with multiple instances alltogether & some big-scaled ones…
solved setting sort mode to “none” from previous “view distance”.

maybe this or something regarding z-depth could solve?

more info on my case:
UE 4.27,
Forward/deferred rendering,
Instanced stereo on/off, separate translucency on/off, DX11/12,
VR game, shows more often using Liv with SteamVR