[Sidefx-houdini-list] Smorganic

Ozgur Yılmaz eoyilmaz at gmail.com
Mon Apr 19 03:11:33 EDT 2010


Actually Pablo, you are right, a solution that works, at the end of the day,
is a solution, no matter what have been used to reach the goal. I support
your point of view. I was just saying that the guys haven't used a technique
that can be done by using SOPs.

Cheers....

E.Ozgur Yilmaz
Lead Technical Director
www.ozgurfx.com


2010/4/18 Pablo Giménez <pablogipi at gmail.com>

> 2010/4/18 Ozgur Yılmaz <eoyilmaz at gmail.com>
>
> > Pablo, if you can download the videos in their site, you can actually see
> > the thin layer of particles that they are talking about. So it doesn't
> seem
> > to me like that they are doing some trick in surfacing phase, but instead
> > they are filling new particles in specific places, specifically the
> places
> > where the holes are going to form.
> >
> I got your point. And I am pretty sure their system is better than some
> massage in surfacing, more complex and probably more exact in terms of
> maths.
> But I have to deal with this kind of problems with fluids several times,
> and
> sometimes the more complex solution is not the best.
> I have worked with several RF artists I have used it a lot indeed, and many
> problems they can´t solve just because RF is basically a fluid solver can
> be
> solved with SOPs.
> At the end of the day you have to get the proper look. I remember one time
> trying to getting a very thin layer of fluid, from some RF particles, as
> they point in their article it was really difficult due to resolution
> limitations, basically due to limitation in the SPH workflow, you need to.
> Solution, just get a more thick surface wich fills all the holes and then
> use a custom peak done in VOPs which make the layer thinner using some
> atributes. job done.
> Is just an example and I don´t want to say the stuff they are doing is bad,
> just recall that sometimes you don´t need rocket science to solve a
> problem,
> just be smart and notice the details that makes something work, and have in
> your hands the tool to modify your geometry/data to make it.
> And BTW, the problem they want to solve is at small scales, grid solvers
> work really well at this scales and you can create an isosurface from it,
> and have all the data at your hands from the DOP operators, even
> divergence,
> and use these data in any other context in Houdini.
> Probably I am wrong, but as I have said before sometimes effects TD
> solutions are better than engineers solutions.
> Appart from this RF is an excellent tool and I have several friends at
> NextLimit so no worries here :)
>
>
> > As they have explained in the interview, this places where a hole is
> going
> > to form actually can be found by calculating the divergences of the
> > particles. I haven't tested this idea though, so I'm sure there are some
> > other things that they keep as a secret.
> >
> > I've generated particles where the density gets lower a threshold, but as
> > the Fusion CI guys said there are sudden explosions when you do something
> > like that. So you also need to keep track of the inner pressure to
> prevent
> > explosions in the simulation.
> >
> > So the whole idea should be something like that, calculate each particles
> > divergence, and if the divergence goes below a threshold (may be negative
> > divergence is enough, I need to check it), then check the pressure at
> that
> > position and if the pressure goes also below a threshold emit a new
> > particle
> > at this position, and may inherit the attributes from the neighbour
> > particles ( again I haven't tested anything). Though, these are bare
> ideas,
> > this Monday I'm going to look at these ideas, when I get back to work.
> >
> > Cheers.
> >
> > E.Ozgur Yilmaz
> > Lead Technical Director
> > www.ozgurfx.com
> >
> >
> > 2010/4/18 Pablo Giménez <pablogipi at gmail.com>
> >
> > > I remembered this article about Smorganic.
> > > After reading it and having done some similar work before in Houdini,
> the
> > > main thing the people from Fusion CI is doing is just slving the lack
> of
> > > deontrol in the RF mesher, basically doing stuff you can do in SOPs.
> > > Fluid solvers can get nice results at mid scales but not a so small
> > scales,
> > > that´s truth, but you can get the overall motion sing SPH or grid
> > solvers,
> > > the trick is the look. Their main achieve is to get a smooth thin layer
> > of
> > > geometry from the particles created in RF. This is perfectly doable in
> > SOP
> > > using particles created from DOPS or even RF. I remember doing simialr
> > > stuff
> > > some years ago in the H8 times using RF particles in Houdini to get a
> > > decent
> > > mesh.
> > > Then you have a plethora of tools like Particle surfacer, Smooth,
> Preak,
> > > magnet, Convert, etc ... to get a nice mesh in Houdini.
> > > Finally to get the finest and high frequency details you have
> > displacement
> > > shaders on your arsenal.
> > > Voila Smorganic!
> > > I have seen lots of amazing sims from these guys but the stuff  around
> > > smorganinc is just marketing around some techniques to fix and massage
> > > meshes created from particles simulated using SPH. Stuf that Houdini
> TDs
> > > have been done for years.
> > > We have been living with Smorganics and we didn´t know, Oh my godness!
> > > My 2 cents.
> > >
> > > 2010/4/17 Ozgur Yılmaz <eoyilmaz at gmail.com>
> > >
> > > > first of all, David Johnson; you were write about being not specific,
> > > sorry
> > > > about that, as you correctly guessed the thing I want to achieve was
> to
> > > > have
> > > > a continuous thin sheet of water.
> > > >
> > > > Alex and Szymon, thank you for your links, those were very helpful...
> > > >
> > > > After reading the article about smorganic, I remembered that the
> fluid
> > > > motion is estimated as vorticities and divergences about a point, so
> > the
> > > > motion of moving away or moving towards a point called the
> divergence,
> > > and
> > > > moving or spinning around a point is called vorticity. I had a book
> > > > (probably left at the studio) where it was explaining the whole idea
> > > behind
> > > > the fluid dynamics, I need to look at that book again (need to wait
> > till
> > > > Monday :) ).
> > > >
> > > > As Szymon suggested, I need to add my own nodes to the particle fluid
> > > > solver, nodes that searches for low divergent areas and creates new
> > > > particles.
> > > >
> > > > So thank you guys again, you enlightened me.
> > > >
> > > > Cheers...
> > > >
> > > > E.Ozgur Yilmaz
> > > > Lead Technical Director
> > > > www.ozgurfx.com
> > > >
> > > >
> > > > On Sat, Apr 17, 2010 at 9:09 PM, Szymon Kapeniak
> > > > <szymon.kapeniak at gmail.com>wrote:
> > > >
> > > > > Go it. Thanks!:
> > > > >
> > > > >
> > > >
> > >
> >
> http://www.cgw.com/Publications/CGW/2009/Volume-32-Issue-12-Dec-2009-/Viewpoint.aspx
> > > > >
> > > > > 2010/4/17 Alex Czetwertynski <alex at franktheplumber.com>:
> > > > > > If you can find it, get the CGW (Computer Graphics World) issue
> > from
> > > > > > december 09 (the one with Avatar on the cover).  The Fusion CS
> > people
> > > > > > wrote an article on smorganics and how it works within realflow
> > > > > >
> > > > > >
> > > > > > On Apr 17, 2010, at 7:12 AM, François Duchesneau wrote:
> > > > > >
> > > > > >> And with a Vop Pop you can have lots of control on the behavior
> of
> > > the
> > > > > >> global force and letting the sph make the particles stick
> > together.
> > > > > >>
> > > > > >> François
> > > > > >>
> > > > > >> Szymon Kapeniak wrote:
> > > > > >>>>> I've looked at the orbit node but it seems like it orbits a
> > bunch
> > > > > >>>>> of
> > > > > >>>>> particles around another particle, my problem is to fill new
> > > > > >>>>> particles
> > > > > >>>>> (probably to a position where the density is below a
> threshold)
> > > > > >>>>> into a
> > > > > >>>>> fluid
> > > > > >>>>> simulation...
> > > > > >>>>>
> > > > > >>>>> I'm quite new in DOPs/POPs in houdini (although I'm much more
> > > > > >>>>> experienced
> > > > > >>>>> with SOPs), so I don't know how to setup a system that adds
> new
> > > > > >>>>> particles
> > > > > >>>>> to
> > > > > >>>>> an ongoing simulation...
> > > > > >>>>>
> > > > > >>>>> Thank you...
> > > > > >>>>>
> > > > > >>>
> > > > > >>> How close you can come to Fusion demos this is another story of
> > > > > >>> course, but my suggestion would be to dive into sph solver in
> > DOPs
> > > > > >>> and
> > > > > >>> look around. Basically it consists with a series of
> microsolvers
> > > > > >>> computing different qualities of fluids. You can turn on / turn
> > off
> > > > > >>> any of them (open asset and start play with it) - I think only
> > > > > >>> density
> > > > > >>> is mandatory for other solvers to work properly. You can for
> > > example
> > > > > >>> turn off all external forces and pipe a pop solver instead to a
> > > > > >>> chain.
> > > > > >>> If you point it to a pop network (like the one created for you
> by
> > a
> > > > > >>> shelf tool "Particle Fluid from Object", you can control fluids
> > > like
> > > > > >>> they were particles, but they look rather like computed by sph.
> I
> > > > > >>> suspect this is what is happening in Fusion demos inside RF.
> > > > > >>>
> > > > > >>>
> > > > > >>>> 2010/4/17 Alex Czetwertynski <alex at franktheplumber.com>:
> > > > > >>>> I was at a presentation at DMALA where the Fusion guy was
> > showing
> > > > > >>>> this.  He made a big point about it being a Realflow solution
> > > only.
> > > > > >>>>
> > > > > >>>
> > > > > >>> Perhaps in terms of amount of particles which practically can
> be
> > > > > >>> computed, this can be done by RF only.
> > > > > >>>
> > > > > >>>
> > > > > >>>> I think you should have been more specific in what about the
> > > > > >>>> example you
> > > > > >>>> were looking to recreate. François' suggestion of the orbit
> pop
> > > > > >>>> would be for
> > > > > >>>> making the particles move in the vortex, but my guess is that
> > > > > >>>> you're trying
> > > > > >>>> to make the water stay in a nice thin sheet as it moves. That
> is
> > a
> > > > > >>>> much
> > > > > >>>> harder task. Maybe you could contact the guy from Fusion CIS
> to
> > > > > >>>> see if you
> > > > > >>>> could license his solver and use it in DOPs. Just a thought.
> > > > > >>>>
> > > > > >>>>
> > > > > >>>
> > > > > >>> Aren't they using vanilla Realflow with custom scripting?
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> > >
> > > --
> > > Un saludo
> > > Best Regards
> > > Pablo Giménez
> > > _______________________________________________
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>
>
> --
> Un saludo
> Best Regards
> Pablo Giménez
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