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Full Version: How to make particles blink in and out at random?

Root » Houdini Indie and Apprentice » How to make particles blink in and out at random?

KeetonSims

Sept. 14, 2021 10:55:18

I'm currently working on a very basic particle system with particles that are meant to glow like embers. Does anyone know how to make them fade in and out at random like fireflies?

toonafish

Sept. 16, 2021 10:08:40

Maybe use an animated Cd attribute noise for the particles, and pipe that with a color correction to increase the contrast into the emission channel of the shader to drive the glow ?

R.

KeetonSims

Sept. 16, 2021 11:01:10

Awesome idea I'll give it a try!

dhuiting

Aug. 14, 2023 07:10:23

I'm trying to do this same thing, did this work? If so, can I see a screenshot of the nodes you used and some settings? I'm trying to do a similar thing but using Octane.

eaniix

Aug. 14, 2023 13:56:43

here's a solution using vex

i@id = @ptnum;
float speed = chf('speed');
float rand = rand(@id) * PI;
float randintensity = chf('randintensity');

rand = lerp(1, rand, randintensity);
rand = sin(@Time * speed + rand);
rand = fit11(rand, 0, 1);
rand = chramp('falloff', rand);

vector colorramp = chramp('colorramp', rand);

@Cd = colorramp;

if your particles are coming from POP, just use the existing id attribute. instead of the random function, you could also use a noised attribute that you created with an attribute noise sop (float)

i like this setup because you can gradually introduce randomness and using the falloff ramp create even more complex blinking patterns. make sure to change the colorramp from float to rgb in the "edit parameter interface" menu