How to set up this simple fountain?

Discussions about the use of Realflow
numerobis
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How to set up this simple fountain?

Postby numerobis » Fri Oct 06, 2017 3:45 pm

Hi,

i'm completely new to Realflow (testing v10 demo) and i'm trying to recreate the attached simple fountain. One problem i have is that the fountain gets much wider and spread out when it breaks at the top. Is there some parameter where i can adjust this?
And the other qustion would be: can i create splashes/spray with standard emitters or do i have to use Hybrido emitters for that? ...and if yes, ist there a good tutorial about creating fountains with Hybrido emitters? I can't get it to work... :roll:

Image

Image

Thanks!


Forester
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Re: How to set up this simple fountain?

Postby Forester » Sat Oct 07, 2017 4:32 pm

These spear-shaped fountains are very difficult to create in Realflow. It has taken me almost a year to figure out how to create these in any reliable way. :)

The trick is to use two emitters (either in Dyverso or the Standard Particle Emission solver), one of which has the diameter you wish for the fountain, and another in basically the same position and orientation that has a much smaller diameter. The smaller one, breaking through the larger one will prevent the uniform dome shape. Getting the "look" you wish for your particular fountain will require a lot of experimentation.

I've spent quite a lot of time experimenting with the Noise, Attractor, Tractor and other daemons, with very poor results. (Just to save you some work and time).

There are three basic ways to create splashes and sprays. One, simply use another emitter with a different mesher (and white material).

Two, use the domain/container transfer technique to convert water particles to foam and back again to water. (If you are new to Realflow, use the Filter Deamon for this purpose.) Again, you'll need to use a second mesher (one mesher for water with water material applied to it and a second mesher with white material applied to it for foam). The operation of the Filter Daemon is explained in the Help file under "Parameter Reference" | "Realflow Nodes" |"Daemons" | "Daemon-Filter." Essentially, you create two domains (for Dyverso) or two containers (for the Standard SPH solver), and then transfer water particles at some point from the first domain (water) to the second domain (foam). The Filter Daemon requires you to specify the condition that triggers the transfer (for examples, when the particles fall to a specified height, or reach a specified age, or when they collide with some object). The transferred particles retain their trajectory and speed so they look pretty natural. If you assign a white color or material to the transferred particles, they'll most of the time look like foam. You can use more than one of these Filter Daemons, so you can do things like transfer water to foam and foam back to water, if you wish.

There is a complete demonstration/example file in the RF10 Demo files. It is under the Generic Catagory and is called "Filter Daemon Basic."

The third way is to use a Phython script to transfer water particles to another domain or container to become foam. Many scripts for this purpose are published on this website in the Python section. Personally, I prefer this method as I can write in some randomizations, make a more graduated transition and add various complexities so that the results are more realistic. But scripting may not be your thing.

There are hundreds of examples of fountains with foam and spray on my website http://www.expandingwave.com almost all of which are using either Dyverso or the standard SPH solver. Unfortunately, I did not add foam to my Free Realflow Fountain, so that one won't be of any help to you - don't download that one looking for help. If you are still having difficulties with foam and spray, write back here again. It may be that I can find some time to create a sample scene for you.

numerobis
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Joined: Fri Oct 06, 2017 3:18 pm

Re: How to set up this simple fountain?

Postby numerobis » Sat Oct 07, 2017 5:43 pm

Thanks for this detailed explanation!
What's the difference between a standard, Diverso and Hybrido emitters?
When i would buy this scene http://www.expandingwave.com/product/wa ... l-scene-1/
ist there a way to transfer this to a flat surface without the basin? And add splashes and spray?

One other question... is it possible to export MXS files of single frames?

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tsn
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Re: How to set up this simple fountain?

Postby tsn » Sun Oct 08, 2017 12:38 pm

Forester has given you lots of useful tips already, so maybe just some additions from my side.

Here's a description of RF's various fluid solver types: http://blog.realflow.com/technology/glo ... ver-types/

I don't recommend the standard particle solver anymore, as long as you don't have some specific requirements like freezing particles via Python scripts or custom daemons. The Dyverso "Liquid-SPH" type (Dyverso domain > Node Params > Particles > Type) is based on the same method as the standard particles, but it's way faster and supports the GPU. Anyway, you should be careful with particle shifting methods (filter daemon, script, etc.) and the GPU: currently this combination is not very stable and you might experience crashes, but of course you can give it a try.

The filter daemon in RF10.1 now has random parameters as well and this might save you from dealing with Python.

Instead of meshing the foam maybe you want to try to render these particles. With some motion blur, and Maxwell Render's "MultiPoint" option, you're able to render really believable foam. If you have it you can also use Krakatoa to apply a volumetric shader. And if the number of foam particles is not high enough then I suggest to enable the filter daemon's "split" option and set it to something between 1 and 4. This way you'll get a denser foam particle cloud and better rendering results.

Cheers,
Thomas

Forester
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Re: How to set up this simple fountain?

Postby Forester » Sun Oct 08, 2017 2:08 pm

Numerobis, you should not buy that particular Water Wall scene from me. You are using the Demo version of Realflow - which will not "read" scene files made for the regular version of Realflow. The Demo version of Realflow is limited to reading scene files made in a Demo version of the software.
Also, please note that I did not use the "spear-shape" technique for those fountains.

If you really want a complete tutorial, I can make you a version of the scene file set for the RF Demo version if you wish, and yes, you can delete the basin structures for the fountain, and move the emitters to any locations you wish. And you can add additional splashes and spray. I can set up the scene to your specifications and provide complete documentation, for the same price as the original scene, if you like.

But I think you might be able to reconstruct this with just a little help. Here are the relevant scene settings taken from the documentation that that accompanies this product package.

First, the components of the scene -- Image

Second, the settings for the first filter -- Image

Third, the settings for the second filter -- Image

If you do really want a complete tutorial, perhaps with the spear-shaped fountains, please go to the Expandingwave site and use the Contact page to send me a personal message there with your requirements. I am happy to do custom work and build custom tutorials for people for a very small price.

Forester
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Re: How to set up this simple fountain?

Postby Forester » Mon Oct 09, 2017 2:11 pm

Here are the settings for a "spearplume" type fountain, and an explanation. You can recreate this in your Demo version of Realflow, and experiment to get the exact effect you wish.

Here's an image of the plume I set up for you to look more or less like those in your reference picture -- Image

And here are the basic components of your scene --

Image

As I said earlier, the basic technique uses two emitters, positioned at exactly the same spot and in the same orientation. But the two emitters are of different diameter sizes. I've called these "DY_Inner" and "DY_Outer" . One of these has a diameter of 0.03 and the other has a diameter of 0.02, to make this fountain very thin as in your reference image. Because these are thin, I increased the number of simulation steps to 400 (from the default 200 steps) in order to allow this fountain sufficient time to form completely. (You can adjust any of these settings later, to make the fountain any way you wish, and to make the simulation run for as little or as much time as you wish. This setup is just to demonstrate the basic techniques, and give you something to play with.)

The key factor in the technique is the "kill_Age" daemon. You are going to use a kill_Age daemon to stop the downward flow of one of the emitters so as to limit the depth of the falling head part of the plume. By "depth" of the falling head, I mean to describe the length of the falling head portion of the fountain.

In the Dyverso solver, a daemon can be connected to a domain (most of the time), but not to an emitter. Therefore, if we want to apply different kill-age daemons to our inner and outer emitters, we need to use two domains. We are assigning one emitter, and the kill-Age daemon that controls that emitter to one domain. The second emitter and its kill_Age daemon is assigned to the second domain. In this way, the age at which the particles are killed can be controlled exactly, as can the diameter of the emitter, its vertical and horizontal randomness, and the resolution of its domain. In this example, one of the kill_Age daemons is set to kill the particles at an age of 90, and the other kills the particles at an age of 10. Mostly, I set this example up in this way so that you can experiment with each of these settings to see what effect each of them will have on the shape of your plume fountain.

Here are the exact settings I used for the Inner Emitter --

Image

Here they are for the Outer Emitter --

Image

and please note that I gave each Domain a resolution of 10 or 20, but only after I tweaked the emitter and kill-Age daemon settings to get the desired shape of the fountain. When you are working with Realflow, you always want to keep the default Resolution setting to 1.0 (or less) until you obtain the desired shape of your fountain or other fluid. Increase the resolution only when you are satisfied with your general result. More particles (as a result of higher resolution) will slow down your machine.

Image

OK ?

Forester
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Re: How to set up this simple fountain?

Postby Forester » Mon Oct 09, 2017 8:29 pm

Playing with this a bit more today. Here is a simpler alternate method that would work for your particular scene. This method does not require two emitters for each fountain plume. Just a single Dyverso Domain and emitter for each plume fountain. The kill_Age Daemon is still key to creating a wider head at the top of the fountain, whose length is controlled by the age of the daemon.

The Attractor Daemon settings are adjustable. Stronger settings keep the particles at the head of the plume closer to the main body of the plume. The Noise Daemon provides necessary variation in the overall shape of the head of the plume.

Image

Each plume needs to have its own domain and emitter, and each needs to have its own Noise, Attractor and kill_Age deamon set attached to that domain. The advantage of this technique is that you can have quite a lot of plumes that fountain and render quickly - half the computer resources needed, compared to the first technique.

This technique does not create a great regularly-shaped spear plume top, but for your purposes, with many spaced out plumes, it does well enough. It creates enough variation to make a set of individual fountain plumes look pretty much like those in your reference picture. Making small variations in the settings of the daemons for each plume will vary the plumes quite a bit.

To make splashes and sprays near the ground, I would use one more Dyverso domain and a square emitter scaled large enough to cover your "pavement". I would position that square emitter near the ground with the emitter pointed downward to the pavement. I would reduce the resolution of the emitter to 0.01, increase the horizontal random setting to a value of 10.0, and decrease the speed setting to 0.5, cutting it off to a value of 0.0 after a few simulation steps. This will give you a diverse number of individual particles that bounce around on your pavement to form splashes and sprays. You can make small increase adjustments to the Object Interaction | Bounce setting for the pavement to scatter those particles even more randomly.

Again, only once you have general shapes you like, then increase the Resolution (i.e., density) of each plume's domain.

I tried this and it made a good simulation that moved along pretty quickly.


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