topic Re: Particles emitting from particles in Bifrost Forum

Particles emitting from particles

max_schoenherr — Sun, 28 Nov 2021 13:21:16 GMT

hi,

i'm preparing a tutorial about particles emitting particles using the nParticle world. the "trick" is to convert the first emission into polygons. not very elegant, but pragmatic.

i thought this should be simple and more direct with BIF graph and gave it a shot for 10 minutes or so. see the screenshot. it does not work. when i directly plug the first simulation into the output as well as the second, i get two independent emissions.

what am i missing? thanks,

----maximilian

Re: Particles emitting from particles

mjcg91 — Sun, 28 Nov 2021 15:38:01 GMT

It works for me. Same graph and default settings on all nodes.

Re: Particles emitting from particles

mspeer — Sun, 28 Nov 2021 16:13:11 GMT

Hi!

It works here too.

Re: Particles emitting from particles

max_schoenherr — Sun, 28 Nov 2021 16:42:32 GMT

just wanted to say thanks! i had to change the appearance of the second emission to distinguish it from the first one.

Re: Particles emitting from particles

mspeer — Sun, 28 Nov 2021 16:48:20 GMT

Hi!

I guess now I know what he means.

The particles of the first simulation are not output after the second simulation.

That's correct, because only the emitted particles of the second simulation are part of the second simulation, so these are indeed 2 independent simulations and particle objects.

(It's the same with nParticles.)

If you want you can combine all particles into one single object by using the add_points node, but I recommend to keep them as individual objects for better flexibility.

Re: Particles emitting from particles

max_schoenherr — Sun, 28 Nov 2021 16:58:59 GMT

very well said. i was aware of the fact that the first emission needs a direct connection to the output node. for the tutorial i‘ll have to set up two arnold materials for a better separation of the two streams. when i work in other modules of maya i get a bit rusty when diving back into the BIF world. grüße aus köln!

Re: Particles emitting from particles

max_schoenherr — Mon, 29 Nov 2021 21:34:47 GMT

additional question: the secondary particle emission (let me call it P2) inherits the particle size from the first one (P1). when i increase the size of the particles in P1, the particles in P2 get bigger as well. changing the size of the P2 particles has no effect.

i guess, what i'll have to do is exclude the particle size transfer from P1 to P2. but how?

Re: Particles emitting from particles

sepu6 — Mon, 29 Nov 2021 21:48:04 GMT

delete the size attribute from the particle filter, so it doesn't transfer from the first particle system, that should do it.

Re: Particles emitting from particles

max_schoenherr — Mon, 29 Nov 2021 22:22:01 GMT

great, thanks!

Re: Particles emitting from particles

sepu6 — Mon, 29 Nov 2021 22:39:05 GMT

I answered without looking at your file. Sorry about that. You aren't using the filter so what you can do is either connect a field to the size or set_geo, vary_source before you connect to the second particle system and overwrite the size attribute like this.

Re: Particles emitting from particles

max_schoenherr — Mon, 29 Nov 2021 22:24:55 GMT

let me try this alternative solution tomorrow. thanks!

Re: Particles emitting from particles

max_schoenherr — Tue, 30 Nov 2021 18:48:47 GMT

hi @sepu6, i tried all three options you mention above -- none of them worked: the size of the secondary particle emission was not over-written. see the file attached.

what actually did work was the filter_particle node.

Re: Particles emitting from particles

sepu6 — Tue, 30 Nov 2021 19:08:42 GMT

You forgot to add the attribute in the vary_source "point_size", is the same thing if you use the set_geo_proeperty you need to set the attribute that you want to change

Re: Particles emitting from particles

max_schoenherr — Tue, 30 Nov 2021 19:20:07 GMT

this makes sense now. thanks again!

Re: Particles emitting from particles

max_schoenherr — Sun, 05 Dec 2021 00:01:13 GMT

cheers! https://youtu.be/cYp3g-vGu_c