Les Presets RF - Le retour !

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Les Presets RF - Le retour !

Messagepar verbalinsurection » 10 Juil 2011, 12:01

Désolé pour le délai d'attente, mais entre Next Limit à qui il a fallut demander l'autorisation de remettre les presets et mes mains à qui il a fallut demander de travailler... :oops:

Voici donc le retour de nos cher presets RF qui se trouvait avant sur feu RFLabs

Most people, when they start playing with RealFlow, overlook the existence of presets. In this new RFLabs test, we’ll be showing you how to find presets for fluids. To do so, we’ll provide a simple scene to test several emitters with different values for parameters like density, viscosity, internal and external pressure, etc.
The best way to understand how RealFlow works is by running tests with it.

So, open the scene attached called TestingPreset.flw. This scene has been created with all parameters set to default. We have provided four emitters so that you can compare the effects of the different parameter settings.
Below you will find all the primary information about the most important parameters. The descriptions of the parameters which follow are taken from the RF manual. All the tables are linked to videos which show a test scene with four emitters (numbered from left to right):

Resolution
[Default 1.0=1000 particles in a meter^3] The resolution affects the number of particles representing the cloud. A higher resolution will give lighter particles. Typically, this parameter is used to adjust the number of particles needed for a specific fluid. Fewer particles will create coarse effects with less detail. The higher the resolution, the richer and smoother the fluid behavior will be.
Resolution can have a direct impact on simulation times because the more particles there are, the slower the computation will be. And the most important thing is that the mass value is modified internally to keep the initial volume of the particle system.

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Resolution is very sensitive and has an interesting impact on the behavior of the fluid. The higher the value of the resolution, the lower mass value the particles will have (note that there are some instabilities in the fourth fluid at the start of simulation), so in those cases we will have to increase the Int/Ext Pressure value to conserve the same behavior, as you’ll see in the next paragraph.

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Density
Density of the fluid (in Kg/m^3). By increasing the density, the mass of each particle is raised proportionally. This will affect the overall behavior of the particles and how it interacts with other emitters. A high density value tends to make slower, heavier fluids. The default is 1000 for water. As you can see, with lower densities you might get unstable behaviors (See Fluid 1).

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Another effect we can see is the compression in the fourth fluid. To avoid this, Internal Pressure must be compensated, equalizing Internal Pressure to the particle mass. The examples shown were created by varying only Density to see the effect on each of them:

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Internal Pressure
This value affects the forces generated between nearby particles. This is a sensitive value and should be handled carefully. The volume filled by a fluid is affected by the internal pressure. More internal pressure will make the particles fill a greater volume. Set to 0.0 to disable the fluid and gas behavior and make the fluid collapse. High internal pressure makes the fluid explode.

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Observe the behavior of fluids with low internal pressure; you can get a “melt” effect as shown in next video.

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External Pressure
This is an overall force that affects all of the particles in the fluid. The external pressure will keep the fluid compact, and prevent expansion.

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Viscosity
The viscosity is an internal drag force. Fluids like water have a low viscosity (1-5). Use a higher value for oil, honey, etc.

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Surface Tension
This increases the cohesion of the skin of the liquid. This property is useful for obtaining mercury-like effects and can also be used to simulate high viscous effects.

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Controlled detonations!! (Playing with SubSteps)
In most of cases the explosions can be controlled by tuning the min. and max. substeps. The next video shows several set-ups we used in the previous examples where we saw explosions, and have been controlled only adjusting the min substeps.

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When you’ve had a look at the comparative videos, have a go at creating some presets. As you’ve seen, some of the simulations present some instability even when controlled by using compensating forces. In these cases, another solution could be to increase the min sub-steps value to give more quality to the calculations. This can give you impressive effects, as in the next video.

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Now you can use your preset in the scene you want. In this example, I’ve simulated a ‘honey-like’ fluid.



Water :


Plastic paint :


Chocolate :

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You can download the chocolate preset script here.

Resources
Presets Script: fluidPresets by Gustavo_Sanchez-Perez

BatchSim4 RealFlow script: http://www.nextlimit.com/nlscript/news_scripts.php?date=08/09/2008&id=118. This script is very useful, as it allows you to launch several simulation tests. (Only available for a Windows operating system)
This page could be interesting to compare densities. (Remember that RF is not physically correct, but you can still use the values as an orientation to compare with water.) http://www.simetric.co.uk/si_liquids.htm.

And here are some cool slow-mo and physics fluid videos to get a feel for the behaviour of different fluids:
http://www.lucidmovement.com
http://courses.ncssm.edu/hsi/splashes/video/event351.htm
http://pof.aip.org/pof/gallery/2007toc.jsp
http://pof.aip.org/pof/gallery/archives.jsp
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Re: Les Presets RF - Le retour !

Messagepar mrlours » 10 Juil 2011, 16:41

OH c'est trop la classe !!! Un enorme merci Verbal!!!!
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Re: Les Presets RF - Le retour !

Messagepar youwont » 11 Juil 2011, 00:33

je découvre ce forum. Chapeau bas ! Messieurs
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Re: Les Presets RF - Le retour !

Messagepar jfx220 » 13 Juil 2011, 19:30

Excellent !!!
RealFlow est parfois très long a faire ces simu,
et j'avoue que tout ces test sont un gain de temps assez considérable.
Après ce n'est qu'une histoire de scale ^^

Mais vraiment super tout ces test
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Re: Les Presets RF - Le retour !

Messagepar holycause » 20 Août 2011, 15:50

super, merci msieur.
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Re: Les Presets RF - Le retour !

Messagepar phil » 01 Oct 2011, 20:31

Super merci 8-)
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Re: Les Presets RF - Le retour !

Messagepar laurentZ » 27 Mai 2012, 12:28

hello,

merci beaucoup pour tous ces presets...
j'ai 2 questions:
1- ces presets sont ils valables uniquement pour un émetteur à l'echelle 1 ou ???
2- le réglage du min sb steps se fait par ou ? le seul truc que j'ai trouvé c'est dans la partie Filters du ParticuleMesh
et c'est le paramètre @ Steps qui est à 64 par défaut.

Merci encore
@+
Laurent
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Re: Les Presets RF - Le retour !

Messagepar corbingravely » 23 Jan 2014, 10:45

I think this can help me with my project. My project is about a fluid drived torpedo. So what I need to know is; whether the liquid’s pressure would build with the force of the opposing sea water and also if it would affect the real flow of the liquid inside.








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Re: Les Presets RF - Le retour !

Messagepar soulkeeper1234 » 24 Sep 2015, 12:05

The best way to understand how RealFlow works is by running tests with it.
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