When Hardware Ray Tracing is enabled, mesh particles from a Niagara system with “Cast Shadows” enabled invalidate the Lumen Surface Cache. In the video, this seems to occur once all the particles have fallen through the ground. However, if we disable gravity on the emitter, it seems to occur when the particles spawn instead. The triggering factor seems inconsistent, and in fact the issue can come and go when adjusting various properties on the emitter, with no discernable cause.
Steps to Reproduce
- Enable Hardware Ray Tracing in Project Settings.
- Create a Niagara system from Fountain preset .
- Add Mesh Renderer (with basic cube mesh).
- Set Spawn Rate or Spawn Burst Instantaneous to count to high-ish value.
- Place Niagara System in basic level with standard lighting.
- Place cubes around the system as 3 walls and a ceiling to block sunlight but allow some indirect light.
- Observe surface cache resetting on particle loop cycle.
Hello,
Thank you for reaching out.
I’ve been assigned this issue, and we will be looking into Niagara mesh particles invalidating Lumen for you.
Hello,
Thank you for reporting this. I can confirm this issue can be reproduced as described in the latest CL, and have opened a bug report:
The tracker will be visible after it is approved internally at Epic Games and is publicly accessible.
If you have any further questions, please let us know.