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CPU Particles collision using local space


I'm trying to figure out if there is any way to make my CPU particles count as collided if they hit a wall due to using local space.

I got a player which I have added particles to, and I decided to use local space on the particle emitters to prevent the player outrunning the particles.

It collides fine when they hit the ground, but when I move the player, the "use local space" cause the particles to go through walls without colliding with the walls.

Is there any fix for this? (I feel like I have played around with most of the Collision settings, but I might be doing it wrong)

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asked Apr 05 '15 at 10:33 PM in Rendering

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avatar image Lovecraft_K ♦♦ STAFF Apr 06 '15 at 06:06 PM

Hi Tobi100000 -

A few questions to help narrow down the issue. In your Collision module you should have World Static as Collision Type by default. Are your walls a World Static object or are they Dynamic? If Dynamic, have you added a Collision type and selected World Dynamic?

Have you tried to reproduce this with the Default Sprite Emitter, just adding a Collision Module and check Use Local Space?

Any information you can give me on how you have your particle setup in the blueprint as well, is it a component or do you spawn it?

Finally a screenshot of the particle behavior also might help identify the issue.

Thank You

Eric Ketchum

avatar image Tobi100000 Apr 06 '15 at 09:30 PM

Hello Eric

What I am trying to create is a rain effect using CPU particles. The particles are set as a component that is using the local space of my character. Since the Target Arm length of my CameraBoom can be zoomed out to 1000, I have set the Z value of my particles to start at 1000.

I am using the standard ThirdPersonExampleMap where the walls are Static and the Collision Presets are set to "BlockAll".

-The first picture you will see the rain particles go through the wall when I walk backwards away from the wall (you won't be able to see many as they fall a bit fast). alt text

-The Second picture you will be able to see that I have a roof over the place to simulate being "inside" alt text

-The last picture are just to show the collision settings of the particles themself. alt text

For the Character Blueprint, the particles are set to be deactivated by default, and I have bound the button "z" to activate/deactivate them depending on if they are active or not.

avatar image Lovecraft_K ♦♦ STAFF Apr 07 '15 at 09:00 PM

Hi Tobi -

Once I had a clearer idea of what you are trying to achieve, I was able to pull out my version of this same effect. My question to you is why are you using Local Space for this effect. I have a similar setup with a Particle System in My Character Blueprint and do not have Local Space turned on and the effect works fine. I just made sure that the Particle System is attached to the movement (Capsule) component of the My Character Blueprint.

Eric Ketchum

avatar image Tobi100000 Apr 08 '15 at 01:27 AM

Hi Eric,

I tried to first make the effect with GPU particles but got a problem with the particles going through the roof if I didn't look at it, which was the reason I turned over to use CPU particles. CPU particles however seems to maxed at 1000 particles (which how I understand is because the CPU can't handle as many particles as the GPU).

To make my rain look okay (since I only got 3000 rain particles), I had to scale down the spawn location to be in a 2000x2000x1000 area (otherwise the rain wouldn't look great), and here comes the problem. Since my camera can get zoomed out by 1000, and my radius for the particles are 1000, causes it to be very easy to outrun the particles (which is why I turned Local Space on)

avatar image Lovecraft_K ♦♦ STAFF Apr 08 '15 at 06:58 PM

Hi Tobi -

If you wouldn't mind take a look at this test project and let me know if the solution will work for you and if not let me know specifically to that project how you have it setup differently.

Thank You

Eric Ketchum

Test Project

avatar image Tobi100000 Apr 08 '15 at 09:58 PM

Hi Eric,

Looking at the project, what I am trying to do different, is for the rain to not stop when you go under some roof (as in, I want people to be able to look outside the window and still see the rain.) which is the main reason I only use CPU particles.

If I had a way to make the rain with GPU particles, and have them not go through the roof (while still being active), I would be doing that.

The reason for using Local Space on my character again, is because of him being able to outrun it otherwise.

What I am doing in my blueprint is to just activate / deactivate the particles

avatar image Lovecraft_K ♦♦ STAFF Apr 10 '15 at 05:37 PM

Hi Tobi -

Can you give me a screenshot of your character's blueprint's Viewport Component List?

Thank You

Eric Ketchum

avatar image Tobi100000 Apr 10 '15 at 07:11 PM

Hi Eric

Here's the screenshot alt text

component list.png (476.3 kB)
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