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squardis

Houdini Flip for small fluids (bottle)??

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Hi,

I try to get some small movement of a bottle out of the water in 3 sec. just rising..
Is flip capable of doing this?

 

I dont see that much stickyness with a high proxy volume collision in real scale (0.3 Units high) for the bottle.

stickyness is on ofcourse, trailsop for V before the vdb collision volume.

is there something i forgot to adjust if you work with small scales?

 

thnx

Edited by squardis

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Let me understand something, you are trying to translate a bottle up and let the water fall behind?

 

It's not very clear what you need to do, but it should be doable, I've been playing with small scale Flips a lot lately..

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Let me understand something, you are trying to translate a bottle up and let the water fall behind?

 

It's not very clear what you need to do, but it should be doable, I've been playing with small scale Flips a lot lately..

Hi Diego,

Yes thats exactly what i want.

Just a bottle rising up and the water that falls along the curves of the bottle and creates some ripples in the water.

 

It just doesnt give me much movement of the water on the bottle or on the flattank surface.

Edited by squardis

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From my experience, flip and small scale are not very good friends, you should be try something with sph, but the sph solver iin houdini is really slow.

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Can you just scale everything up pre-sim, then scale it back down post?

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I agree with Ivan in that FLIPs tend to require work for smaller scales. If I were you, though, I wouldn´t get close to the SPH solver, not even to touch it with a long stick  :P

 

I´d rather "help" the FLIP solver with some clever velocity attribute massaging, maybe though a clever "pumping" .

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Can you just scale everything up pre-sim, then scale it back down post?

 

That doesn´t work in many situations. You might end up with a glass of water that looks like a major flooding. You don´t just want to change the scale, but the scale of the details, and that´s simulation-dependant.

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That doesn´t work in many situations. You might end up with a glass of water that looks like a major flooding. You don´t just want to change the scale, but the scale of the details, and that´s simulation-dependant.

 

Well, scaling it up is not a bad idea at all. As long as you keep in mind that your forces will change and so on.

Scaling it up pre-sim, changing the "spartial scale" value in the flip-solver(Tab Volume motion , Tab Solver) also a bit of tweaking to your forces, time scale, and so on. Sometimes I don't even change the spartial scale and just play with the forces in the Sim to achieve the wanted effect. But yeah don't touch the SPH-solver.

 

So yeah, what I am trying to say is that the main idea of scaling it up is not bad. But as Javier was saying how you adjust your sim in order to match your ref will always be a different struggle.

Edited by Hudson

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I've found FLIP can handle small scale okay -- the biggest issue is that the forces and collisions (movement of the bottle) is large compared to the size of the fluid.  If your collision object is well defined, then it's usually a matter of substepping the simulation much more than usual - usually at the DOPnet level, but you can get there using the Min/Max Substeps on the FLIP Solver itself.

 

 

On the other hand, I've seen a simple emulation work for fluid in bottles where you essentially Clip the the fluid volume to get the the water level with a wobbly up-vector, and noise up the surface with very low-freq noise. You can do the wobbling of the up-vector using dynamics.

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well i am pretty new to H FLIP but if you want very clean stuff for commercial work where they want very smooth stuff etc ...

i must say it was extremely painful / hardcore to get this with H FLIP ! I have see very very few clean stuff for commercial packshot done on vimeo with H Flip.

 

The only guy i have see that get perfect stuff is Pazuzu

 

But he looks to be a sort of jedi in this area, so chance are that you won't reach his level.

All this to say that i probably would pick Realflow 2015 in SPH mode if i had to do a commercial packshot next time.

 

Just to give you some perspective ...

 

Cheers

 

E

Edited by sebkaine

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The coca-cola filling at 00:50 here was done by my good friend Hudson with FLIP:

(didn't notice he replied to this thread already, but here it is anyway)

And rendered with Mantra of course.

 

I don't know why, but it definitely isn't as impossible as most seem to say here. Just keep in mind that it is small-scale, so the same workflow for big oceans or waterfalls might not be appropriate. 

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Wow,

I'm glad so many experts chimed in.

 

I agree with all of you, about the fact the small scale FLips are quite hard to handle, but not impossible. I have done some liquid sloshing inside a container before.

Alejandro seems to be very great at small scale FLips.

 

Probably RealFlow would be a good solution for doing commercials, as Emmanuel mentioned.

Anyway, if you decide to go the H route, it won't be easy but certainly achievable.

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That doesn´t work in many situations. You might end up with a glass of water that looks like a major flooding. You don´t just want to change the scale, but the scale of the details, and that´s simulation-dependant.

 

I understand; like transposing a music scale, it's not as simple as it sounds. But, you don't necessarily have to move out of real-world measurements; scaling by 100 and changing your dop units to centimeters is a good example, but you might want to change your mass measurements as well. Now, all of your force values are relatively abstract. However, if you lay down a gravity node, it will give you the proper value/unit. You can use this as a jumping off point to transposing force values.

 

Every method has it's own caveats, ultimately; your desired end result should drive your decision in which method to use.

 

>/\<

Edited by 3iart
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Of course there are a lot of ways to archive small scale shots in houdini using flip, but from far small scale is always better to do it using sph, much more accuracy than flip.

From my side i recommend realflow for that, from far! But you can try as Hudson say, to scale up the scene.

Best Cocacola Commercial ever! Great work Hudsoninho and David!! ;).

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imho, Houdini can handle every scale fine, its solver is just build not for small scale , but even then in Houdini you are free to dive inside the FLIP solver :D

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