How to hold or wave particle

Hi there,

We have developed a scene which the Mushroom will change size and explode, After explosion, it just like sparkling object hanging in air and slowly flow down.
I want to use the HTC VIVE controller act as both hands to hold on the particle when sparkling comes down, Also, when I wave hands (Controller), those sparkling will also move away.

Can someone please show me how to do these two methods?


Have you tried to add collision to the particles?

When you add collision they should land on the hand and not go through any more. I don’t know if they can also receive any impulse from the collision event (I think they can only give impulse to other objects), so waving them away might not work that well.

We have added collision to particles, but it didn’t help.
Issued: it holds only one layer, which particles can’t stack on top of others.
when hands(controller) release the action, particle stays in air… …it won’t continuous drop to floor.

When trigger, it flow away from controller (hands). Plus, waving method still not success. Just like hitting baseball, not nature at all.

Don’t have a clear picture of what the scene make-up is / what its all about, got pics / vids?
But I know if I was trying to do this task myself I’d be using smoke & mirrors every time etc.

In other words I’d have smoke / fire particles plus I’d spawn in some meshes with physics.
Then I’d try blending everything so that I ended up with something I could actually control.
For example can particles or fractured mesh parts even be controlled in UE4 using BP etc???

So the scene might start out with a barrage of particles blended with physics driven meshes.
But it would later switch to movable meshes / physics objects that are more deterministic.

Obviously its far easier to do this in scenes that are fire laden with smoke fueled explosions.
Whereas you haven’t shown us what the scene is, and what you have to do deal with here…:slight_smile:

Hi Franktech,

Due to company policy, I am unable to release any pictures or videos…
The following is our Scene Concept. (We use HTC Vive to experience the event and also interactive (Controller will display as hand) within the Scene)

There will be a giant (2m height) Ganoderma (Blueprint) on floor, when Viewer walk toward to Ganoderma, viewer able to look under the Ganoderma bottom layer.
3 second later, bottom layer will release very small spore (particles) “like sparking flowing in the air and drop on the floor”.
Now, Viewer should able to use both controllers (act as hand) to catch / hold / wave the spore in the air.

We have added Collision to particle (spore), but it didn’t help too much.
cause when both hands try to hold on the spore in the air, it holds (cause particle set to Freeze), but when hands move away (release), the spore(particle) stays in the air (cause set to freeze), can’t continuous drop to floor. *** not sure how to release the freeze ***
Second, when next spore drops on the same spot/around (on hands), it can’t stack on top of it. (cause setting only allows to bounce away or roll out) *** don’t know how ***
Third, Don’t know how to make wave scenario within the spore, so it makes the spore fly away (like air wave) when viewer wave controller.

Any ideal?

These are UE4 particles or you’re using this just as an expression for tiny meshes?
Not expert @ Cascade, but don’t see how you can do this with UE4 particles anyway.
Instead I’d look to do this with small meshes and Physics Add Impulse / Force etc.
It might even be that you can interp the movements without even using physics etc.
It just depends on the overall goal and desired effect. But some Psuedo-code ideas:

Spores released: Add impulse / force to a mix of different sized meshes with physics.
Continue to add impulses to keep spores floating in the air / let some drop to floor.
Use Tracing to lock onto or target a spore using the VR controller’s world position…
Once a target is chosen limit its movements to interp the controllers movements.
Disable physics to Stack spores once a spore intersects another (rigid bodies repel).
Wave gesture detected? Re-enable physics + re-apply forces to make it float away.

That definitely sounds like it is not possible with vanilla particles (or only with a lot of effort).
I wrote a code plugin which allows you (among other things) to control the particles directly from an object blueprint, so your hands could directly move the particles based on their position:

But I think franktech is right, in this case it would probably be easier to not use particles and let the engine do the heavy lifting.

Hi Cultrarius,

Thx, I tried to go through link, but most of the videos are unable to play.
Error: Unsupported video type or invalid file path

Possible update the video link?

Hey Kelvin,

the videos are encoded with the webm format, which older browser might not be able to play. You should be able to see them with a current build of Chrome/Firefox. If you are using Safari you can watch them by installing the VLC plugin.