VFX Graph - spawning particles from particles

I'm playing around with the new VFX graph and I am unable to work out how to get particles to spawn from particles.

two scenarios I am wanting to tinker with, simple one would be fireworks. so i could fire some particles up into the sky and then spawn a bunch of new particles from them.

and clouds. I have a nice little cloud setup which makes a happy little cloud, but I'd like to have my clouds spawn across the sky. I was thinking it would be reasonable to have a bunch of particles spawn across the sky and from each of them get my puffy clouds to appear.

How can I go about doing this? what node or connection am I missing?

Also, when setting the spawn position of my cloud particles I am using a position(Sphere) node. It allows me to control how much of the sphere the particles will spawn in using the Arc (Angle) This is handy, however there are no controls that I can find for the rotation of the sphere so you can control which parts of the sphere you want particles. The arc angle starts at the bottom and as you slide it back it goes up the side so you can have a hemisphere with the left side as flat. however you can not change that to have the bottom flat. You need to rotate your particle emitter in the scene to get this. I feel there should be a sphere rotation option or something like that connected to the Arc(Angle) option to allow for more control in this

 

Hey Julien, Thanks for this. However I cannot find any trigger blocks to add to my update node. Also I can't find the GPU event node either. There is an Event node, but not a GPU Event.

 

Ah I found this, in case anyone finds their way here.

I needed to enable Experimenal Operators/Blocks in the Edit - Preferences menu

 

Is there some other trick to "enable" the GPU event? I've gotten all the blocks in my graph like in the diagram, but can't find any combination to make the secondary particles spawn, or spawn in a visible way, to be precise. Adding a spawn block throws an error, probably because the GPU event itself is a spawn block. But there's some setting somewhere I'm missing to get this to work. Maybe there's a setting in the HDRP profile???

 

This seems more like a hack than a fix, but if you inspect the Quad Output block for the secondary system, in the inspector window there's a Particle Options > Sort Toggle where the default is set to "Auto". I turned that to "Off" for the Output of the secondary particles and they appeared

Also, now that I can see GPU event particles, it looks like there are many that spawn where the parent particles are spawned rather than where those parents die. Or more likely, some of the parent particles are dead at birth. Whatever the cause, it's unwanted behavior.

And finally, the more you fidget with the system, the more unstable it gets. It feels like the code generation can get into unstable states where subsequent changes are conflicting or ignored. To repro, set up a GPU event on death system and then toggle off the random lifetime block in the parent system, and hit Compile a couple of times and see what happens. Nothing good.Sometimes deleting the gameobject in the scene with the open VEG cleans this up. Sometimes that doesn't work, but restarting the editor helps restore intended graph behavior

 

Same problem as Livealot here. The particles are never spawned....

 

God! TY So Much

 

Be sure to include an Update Particle block. Even if it is empty.
The particles will not spawn without it.