repeating cyclical emission

[Kris Rivel]

Anyone care to point me in the right direction for creating a repeating, cyclical emission?  I need to create some simple fire and electric effects and I need an emission that I can cycle as desired.

Kris

[Fabricio Chamon]

 turbulize emitter value node or use a sin function to modulate the emission rate.

[Kris Rivel]

But isn't it a two headed beast?  Controlling the emission rate with a cycle is one thing but I also need to control the position that the particles are emitted from on the surface.

[Olivier Jeannel]

"Modulate Value Over Time" has a Loop button.

Le 14/09/2011 17:08, Kris Rivel a �crit :

[Ciaran Moloney]

There's a loop value compound. Try passing current frame into that and the result into the emitter seed. But, turn off 'time varying' on the emitter compound, or the emission itself will be time dependent.

Ciaran

[David Barosin]

If I understand the problem, maybe you can cross fade a cache.  Just thinking out loud.  Say the sim is 100 frames cached out.

frame 50 is your loop frame.  So you add the cache to itself with a 50 frame offset  (two cache on file nodes).

At frame 50 it's entirely cache A (without offset), and frame 100 it's entirely cache B (with 50 frame offset)     
Use any type of delete particle trick to blend between the two (i.e. turbulence or just by index). 

[Kris Rivel]

Thanks everyone..making some progress.  I like your idea Dave but sounds over my head.  I can honestly say that I've never tried to blend caches.  I'll give it a go but will probably need some guidance...maybe easier than I'm thinking?

[Andy Moorer]

This should help...

[Kris Rivel]

Thanks Andy!

[Andy Moorer]

(BTW sorry if screenshots are frowned upon, I can never keep track of which list wants what. ;)

If you rip the guts out of a surface/volume emitter it's basically just generating a sample set, passing that set to an add points node, and initializing the necessary particle attributes.

The generate sample set node has a checkbox, "time varying" that you can disable, after which each different seed value corresponds to a specific sampling of positions. So then all you have to do is create a repeating series of seed values... in the screenshot I used a modulo function, or you could use a sinusoidal function etc.

A little hacking at the emit from geometry emitter can give you a nice cyclic/periodic emitter.

[Alan Fregtman]

Screenshots frowned upon?? Whoever frowns on that needs to cheer up
and scale their frown by -1,-1,-1! :p

"A picture is worth a thousand words," or so they say.