Hey,
not really a question, more like a nice surprise for me, because i didn´t know, that the Pathtracer (4.27, the UE 5.0 crashed permanently with this test) and Niagara Particles work together and can even illuminate a scene 
Didn´t know, this was possible.
Took just 3.5 minutes to render this out (128 spatial samples and 32 temporal = 4096 total samples).
And of course, the forum shrinks the 4k original picture to 1920x1080 -.-´
Woah how did you get Niagara particles with Path tracing?!
I actually did nothing special 
It´s a regular project for RTX, that just uses the pathtracer in the Movie Render Queue for rendering. The particles are normal particles with a standard glow material (have tested it with mesh particles and sprite particles, works with both).
Works in 4.27 out of the box, same for 5.1. Even in the regular editor preview you can see the effect already happen, there the particles just get smeared, since path tracer is built up over several frames.
Edit: Even Lumen reacts to them, if i switch to Lumen and use the regular render method.
wow, I Don’t know why but when I try to render it and place a fire or spark particle system in the scene the particles aren’t visible in the viewport or movie render queue. Do you know a work around for this or think I’m doing something wrong?
i am no expert in Niagara, but if your particles even aren´t showing up in the viewport, then something is wrong in your setup or emitter 
Here i tried one of the fires from a free asset pack:
Asset pack: M5 VFX Vol2. Fire and Flames(Niagara) in Visual Effects - UE Marketplace
After raising the glow and fnd after disabling the distorion particles (cuz it needs some serious tweaking for the pathtracer, currently it looks like “plz delete me”) and the smoke, it looked like this. So right now, it´s just all the flames, since those fires didn´t look like they were made with pathtracer in mind ^.^
Here is a 5.1 test from my scene with sprites instead of meshes/cubes:
Yeah I have no Idea what’s happening any more. I tried doing it again but still nothing. this is a pic from a scene with it.
■■■■, having the same issue. I made a fire in a fireplace and it’s visible in editor with pathtracing but when I render it in movie queue it’s not visible. Maybe the niagara animation has several frames that lead up to the spawning of flames and the path tracing doesn’t get there before it finishes the render… Just guessing at this point
Some particles need a warmup time, before they show up in the Movie Render Queue renders. I usually use the default Render Warmup of 32, but also Add Engine Warmup of 500, and then i render the 99. or 100. Frame from the sequence, just to be sure, that the particles had some time to spawn in.
Maybe play with those rates, because i remember, i also had a time, where it looked good in editor, but seemingly not particles were in MRQ, until i played with those warmup rates and started with later frames.
Edit: had tested it, and you def should play with the Editor Warmup value, those give the scene additional frames to spawn in partices. My used Engine Warmup of 500 giving my scene 500 frames for the particles to spawn in and to populate the world, before the very first frame would be rendered.
Thank you so much for this! That was the solution! I tried that before posting my original post but the warmup count was too low and I scratched that idea afterwards. Last night I stayed up until 1am trying to find a solution… Thank you again.
