I have these lines in the middle of my render with rain. I cant fix it, i tried randomize, velocity, changes on emitter but noting works. Anyone have an idea where this come from and how to solve this?
It looks like a bug for me and if nobody knows the issue i would make a bug report. Maybe it is pc / gfx card / driver specific. If someone other render this with the same issues?
I has to do with your particle settings. Set the roundness (whatever this means) under the “regenwolke” Particles>>Children>(simple)>roundness to a value like 0.1. That should solve it. It is how it is with particles and blender. Nobody understands it realy… Or maybe only me does not understand it. Always lots of time with attempt and errors. It is easy to setup and fast but always somekind of shit. Just in my opinion. But i like it. 
Hope it helps you with your scene.
cheers
it worked.
I didnt try this parameter, cause i didnt think it could be an issue, but it is. I guess it needs some specific circumstances to be visible like camera angle and motion blur.
Rounding the children’s appearing area fix it.
yea… maybe send a artists friendly bug report Because this setting is not artist friendly or causes problems. But setting up “usual” Particles that way is much faster then for example with nodes… in my opinion. Maybe this rounding should be default. Have good time and fun!
Yes, i made an report:
https://developer.blender.org/T93216
But with try to recreate the issue i see it is not a bug, the documentation is not clear. The child particles are generated in an plain circle. I would have expected a cube. Maybe the improve the function or the documentation.
You are right. It is not a bug. It is a feature. It is not a circle… more a sphere. This simple children behaving and settings make some kind of sense for some cases. But not when you do not understand what is going on and also the doc does not explain. Especially the relation between roundness and radius. I can handle it but it does not make sense most of the time. It is a feature but not easy to understand every time you need it. have a good time!
