I have a Rain particle, with 2500 units of Cylinder radius. Setup the collision module, with kill event.
And a lot of rain drops leak trough
roof.
I will provide. Give me time to go home. 
Hey -
Can you take a screenshot of the leaking section of your effect and without moving the camera also take a screenshot of the same area with the BufferVisualization >> Scene Depth turned on?
Thank You
Eric Ketchum
Meshes. Im Using 300x300x20 Blocks, with 20x20 vertex grid. Very good UVs and Collision Bounds.
Hey -
I am trying to find a repsroduction of this issue internally. Can you let me know if the walls and ceilign in your level are meshes or BSPs?
Thank You
Eric Ketchum
Hey -
After a little bit of investigation, what you are experiencing is a limitation of how GPU particles receive collision. GPU Collision is done via the Scene Depth Buffer which means it is limited to the camera’s view. Since the roof over your character’s head is not in the camera’s view, the GPU particles do not see it as collision and will fall through it.
Thank You
Eric Ketchum
And there is some Volume to Block it? I´m developing a complete weather system, fully dynamic, to use on exterior/interior scenes.
As some games are open world, so as to produce what I think, what would be the solution to be no rain inside the houses, but still raining to look out the window? If there was some kind of volume, to block, would be perfect.
Here is my Weather System Project: LPV + TOD (Light Propagation Volume + Time of Day) [WIP] - Architecture - Epic Developer Community Forums
In addition, I am suffering with various types of problems with Cascade.
- I can´t make Clouds with Shadows. I mean realy hight clouds (z 150.000).
- When I turn my camera, shadows are flicking.
- In some angles, comes self shadow acnes.
- Realy bad performance with some storm clouds (huge and dense clouds) tryes.
- Rain leaking through roof.
- Probably when I have blizzard, will leak through the walls.
There is a prediction of Niagara? And about Raytraced Shadows casting shadows on Terrain?
(sorry for many of topic questions, but I must take advantage of this direct support of Epic that you are giving.)
Hey -
I will try to address the issues as you listed the above:
The shadows from clouds and the shadow flickering are both a result of fixed bounds issues. I will try to address them more directly in your other issue, but you can set the fixed bounds to an large amount and this should help some, but shadows will still pop in and out if you are turning the camera to eliminate an emitter.
The “Self Shadowing acne” is a result of too many particles overdrawing on top of one another with too high an opacity value. Adjust you opacity or spawn rate downward and this issue will resolve itself, the test map I posted on your other question shows the acne and how I got read of it.
Bad Performance comes from wanting all your clouds to be self-shadowed and shadowing your entire map, this is costly for particles on such a large scale. I would suggest using a Light Function for the large scale clouds shadowing the ground and only self shadow a base level of spawned clouds and use additional filler clouds with no self shadowing to help fill the sky itself (working with a material change of course).
The Rain and Snow leaking can only be fixed in the large scale by spawning CPU particles and not GPU particles. I know ultimately you are wanting to have a universal weather system but a lot of weather systems in games now are catered to run around certain environments for performance savings, so its not really raining everywhere just where you see and when you go “indoors” it is only raining in a thin sheet just outside the door, which is an old movie and theatre trick as well.
Niagara is something we are working hard to finish, but I still have no further information about it yet. Ray Traced Shadows on terrain is on the list as well.
Thank You
Eric Ketchum
Hey rene, try setting your collision Radius Scale to a lot more!
1.0 will make only certain particles to have collision while others will go through objects.
Lemme know if this works 
Hey ,
Have you been able to find a solution or work around to the issue of leaking roofs yet? I’m trying to create a particle system for rain at the moment. And it’s just impossible to find anything on it, on the internet when it comes to collisions.
A unique suggestions I found were creating a volume that would turn the particles invisible. However, I have been unable to create something like that.
No. The best I can do is TURN OFF “master rain” by a trigger volume, and TURN ON some rain sheets on doors and windows. Just like suggested.