Particles Render in the Wrong Order
Effects pop in front or behind each other
Also known as: Particle sorting · Translucency sort priority · Unity particle sorting fudge · Niagara sort mode · Smoke in front of fire · Transparent sorting issue
Quick answer
Particles render in the wrong order because translucent objects are sorted by distance, and overlapping effects or large sprites can sort incorrectly. Set the sort mode on the emitter to sort by distance to the camera, and use priority controls to force an order: Translucency Sort Priority on the component in Unreal Engine, and Sorting Fudge or the renderer's Order in Layer in Unity. Put the effect that should be behind at a lower priority.
How to fix it
Split an effect into separate emitters or systems for layers such as smoke, fire and sparks, then set the order by hand. Avoid very large sprites that intersect other effects, since they sort by their center. Additive particles do not need sorting, because their result does not depend on the order, which is a reason to use them for glows and sparks. Check from different camera angles.
