Flowing non intersecting particles with different pscale

[sizam]

I want to make very popular effect which you can find on 0-4 seconds in video https://vimeo.com/232473927

And I found that only Flip fluid has very cool motion of particles with many swirls which I like. Problem is that I can't see any possibility to use different pscale in Flip simulation.

I can do non intersections only if I use POP and pop grain, but in this case, flow becomes look like wet sand 

 

Is any good way to have organic flow like in flip fluid but keep different pscale and non intersections? P.s. I tried Pop fluid, but flow is not so cool as in Flip solver

 

Edited June 18, 2020 by sizam

[dleonhardt]

You can do a FLIP sim and get the general motion you want there. Then create a second DOPnet and run a POP sim with the POP Advect by Volumes DOP to reference the velocity field of your FLIP sim + the other things you have in mind.

[sizam]

2 hours ago, dleonhardt said:

You can do a FLIP sim and get the general motion you want there. Then create a second DOPnet and run a POP sim with the POP Advect by Volumes DOP to reference the velocity field of your FLIP sim + the other things you have in mind.

this will not solve the main problem with intersections. I tried this also as well as transfer speed value from Flip particles. But, again, I need to add pop grain to avoid intersections and this kills whole look. Tried to find other nodes. Pop interact is cool, but looks like it doesn't support different pscale on particles

[Librarian]

I know exactly what you want ...just after you sim.. feeds this trick ...you gonna see ...Hope it Helps
I did a billion tutorials(following) and just maybe you gonna have the benefit of that :).
h_tricks_scattersrle1125.hiplc
TUTORIALsrlefluid25.hip
 

[toadstorm]

POP Grains will resolve intersections. If you need the collisions to be "softer", you can adjust the collision stiffness.

To get FLIP-like motion, consider running a smoke simulation first, caching out the velocity field, and then advecting your POP grains through that field via POP Advect by Volumes.

[sizam]

33 minutes ago, toadstorm said:

POP Grains will resolve intersections. If you need the collisions to be "softer", you can adjust the collision stiffness.

To get FLIP-like motion, consider running a smoke simulation first, caching out the velocity field, and then advecting your POP grains through that field via POP Advect by Volumes.

tried this early, but still, there are some chunks, I guess because I have a lot of small particles. 

35 minutes ago, Librarian said:

I know exactly what you want ...just after you sim.. feeds this trick ...you gonna see ...Hope it Helps
I did a billion tutorials(following) and just maybe you gonna have the benefit of that :).

It doesn't have a solution for the main problem. I can prevent intersection BEFORE simulation (I like your method also, definitely will save it), I used Relax node on scatter points or MOPS deintersect and there are many other ways. I also can easily import velocity fields from Flip or pyro. Problem is that Flip solvers makes all particles with the same pscale. So, I need to prevent intersections directly in simulation. The only node which can do this is POP grain, but it changes looks of motion and adds some forces as "waves" like in wet sand. 

Finally, I found a temporal solution. I used method https://www.youtube.com/watch?v=qXoSEnh94YQ It allows to keep motion from Flip velocities and resolve intersections. The only downside is very slow simulation if I have millions of small particles.

https://www.screencast.com/t/L1GznhY1mjLy

Maybe someone know some vex or vop for solving intersections for particles with different pscale inside POP. I think that Pop interact must do this, unfortunately, it ignores different pscales

Edited June 18, 2020 by sizam

[toadstorm]

You solve intersections for particles with different pscales with POP Grains. That is the way to do it, unless you want to use Vellum grains, which are certainly viable but might be a little bit slower. POP Interact can only apply forces, which are not going to get you clean collisions. 

 

pop_advect_grains_toadstorm.hiplc

[Librarian]

Like a lot "artists " that don't want to make statement where its made and How? I think that this its made by ..Point-Vortex-Dynamics_on_Closed_Surfaces.
Just search Github and you gonna find Study ..by this Student MARCEL PADILLA.
it s like hearing this Artist explaining an effect like mine Daughter (whats going on in school)..just say its Clebesh surface simple ...Just mine Thoughts
https://vimeo.com/334511184

 

[Librarian]

thanx @toadstorm for your Time

[nuki]

if you need proper collisions use pop grains like the others suggested

if you want to try to use your flip sim I've attempted to use a pretty soft pointrelax (to keep the jitter low, although it should be fairly stable when you do it in your flip dopnet with a few substeps) and a for loop to maximize pscale without intersections. That way pscale is determined by the points distance to its closest neighbour and can change over time (because 'collisions' are soft). Idk, maybe does the trick for you or not

soft_deIntersect.hiplc

Edited June 18, 2020 by nuki

[sizam]

6 hours ago, toadstorm said:

You solve intersections for particles with different pscales with POP Grains. That is the way to do it, unless you want to use Vellum grains, which are certainly viable but might be a little bit slower. POP Interact can only apply forces, which are not going to get you clean collisions. 

 

pop_advect_grains_toadstorm.hiplc

Thank you, this is more close what I want. I tried totally the same logic, but I used FLIP for making volume velocity, you use Smoke solver which is working more natural.

I also tried your volumes in my RBD setup, it's also interesting, a bit buggy and slow, but what I like is that particles keep initial shape more better than with POP grain, can be interesting in some setups

I am attaching two files for those who are interested

 

movingNonintersecting.hiplc

pop_advect_grains_toadstorm_2.hiplc