The particle’s material is translucent. They render fine in all cases except for when I have a mirror behind ( which is exactly where I need them to be). The mirror material is a scene capture cube target into base color (no emissive there).
Here is a ss showing how they render normally:
And here is how they render with the mirror behind (they are almost invisible):
Have you applied Depth Fade to the material? It looks like the fade distance is too large. It’s based on scene depth, so if the ‘back’ of the particles are too close to the mirror it’ll cause them to fade out - which is what happens when they turn to face the camera and you move away. The wall to the right is further from the particles than the mirror, hence they don’t fade out.
SSR Should pick up Particles but I don’t think Reflection Cubes do… could be wrong… you’re not using forward-rendered translucency are you?