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Rain water drips


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Hello everybody,


I'm learning/using particles with Houdini 13 on the old popnetwork. And I'm trying to create myself a water drips effect which slide on an object like here :




You can check my file, where I'm using the Split POP. But the result is not very good. And since morning I'm a little bit stuck.


If you have any idea to help me, thank you in advance.


Edited by sliver
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Adad could you help me for a last thing ? :)


To learn more and more Particles I have decided to download the rain.otl in order to recreate it.

But there is a "strange" node :  SplitPOP called : obstacle_split_single2


When I create a new split with the same parameters, this new split doesn't work for the setup, and when obstacle_split_single2 is actived, the system works. And I don't understand why. There is hidden parameters ?


Thank you very much if you can help me.


Edited by sliver
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Just checked your file, looks like both splits are working, getting 1 birthed particle, what version of houdini are you in? here


not sure why its not working on your end, i dont see anything that would prevent it from working.


Scratch that, I played with it a little more and noticed something was going on with the grouping at the first split, dont think it was preserving the right group (it was still grabbing the name from the old split) , i attached the hip below.






Edited by amorales
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  • 5 months later...

Ok, changed the original setup, which was using the old POPs into a setup using the new particle workflow in DOPs, so it basically works. Of course, the general behaviour can be improved (didn't look so much into that). Anyway I'm not 100% convinced of the trailing behaviour, I'd like to see more...yes trailing behaviour, now it looks a bit scattered, but I do not know how to better control particle emisson from the POP Replicate node. Maybe I should add another POPVOP that will do the emission.






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  • 2 years later...
  • 10 months later...

Hi everyone !

I don't understand the vop way to have particle trails (still trying to learn VOP logic). There is a method to do that without vop? Like the old popnetwork? 

I encounter two problems in the new popnetwork to achieve that with the old way I think:
1) attribtransfer has to give me the normal for sliding particles group and i can't use this node in popnet context
2) I can't group particles with the rule $SLIDING == 1 or $SLIDING == 0 to delimitate sliding and nonsliding particles... I don't know why.

I tried the old way, that's worked but I want to understand how to do that with newer versions.

If someone can help me, that would be really great :)

Ps: I know there is the orbolt asset for rain but I try to make this effect by myself.

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Hi Atom,
Thanks a lot for your answers and share this hipfiles. That's will definitively help me to improve my setup !

In my scene, I already have splash impacts on my object and on the ground. 
The only thing that I can't have is the trail which result of this impacts (moreover my object moving like a car under rain) like in videos below.


EDIT: To be more accurate, my object is not animate but the rain is simulated like the car was moving. 

Edited by Arch
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If you take a close look at the StepByStepVFX file you'll see that the author has copied a tapered line to the falling points. You can increase this line length to make the trails much longer.


Edited by Atom
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  • 6 months later...

Hi guys!  Thanks a lot for your tips!  Inspired by this thread and Josh Clos article (https://www.joshclos.com/procedural-rain-system) I tried to replicate the effect .

I didn't understand why the drops have to stick around the center (due to wrangler in popnet) so I made a group w/ random points from POP Replicate and used wrangler and POP Interact to pull them appart and stop them after a certain age. 

Then used them to compute droplets sliding on surface.

 For puddle, instead of sin() on impact geo, I used a ripple solver, think the render is better for not so much more calculation. 


You can see the system in action w/ another model: 

Hope you enjoy!

Edited by Biscotte
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  • 1 year later...

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