slow river and some splashes

[hatrick]

Hi,

How would you sim a slow floating river with some selective splashes on the surface?

1) A Tank setup frustrates a constant stream. (I tried a ropebelt-like solution where two pumps drive the upper and lower part of container particles in opposite directions, Kind of works but hard to controll !)

2) A Riverbed with a simple sink on the lower end. Here it's hard to controll the speed of the stream against the waterlevel. Like mentioned the river should flow slow.

3) Simulating the splashes in a stagnant container and fakeing the stream after meshing frustrates the deformation and the foam of the splashes floating with the wanted stream.

Thanks a lot for your help

Lucas

[kleer001]

Depends a lot on how much time I have to do it, the camera point of view, and its final display (tv, movies, video games)... Can you tell us more about the context?

[hatrick]

Topview from a bridge onto the slow floating river. FOV is about 6meters. Effect is for Film. A fish ( about 40cm) emerges from the water an breaks the watersurface for a short moment. Dark green dirty water.

Thx

Lucas

[Hudson]

Hi Lucas!

Please excuse my lack of drawing skills. The point of this picture is to present a possible idea of how you could create the right river motion.

If you emitt particles from the yellow source (4) and create two procedural blockades for the fluid (1) and (2). You can controll the flow of the river. (5) and (6) is where you want to kill your particles. (6) is the one keeping the flow going and (5) is just to adjust the waterlevel and it should be put where you want the waterlevel to be. If you build the collision blockades with procedural holes you will be able to adjust the size and shape of the holes and also the speed of the particles in the river.

It will requires a few experiments to get the right speed. But once you get it it should be constant. You could also build the first blockade (2) with the shape of the bridge poles to get the right motion of the flip fluid.

remember that the speed of the river will be a bit odd near the blockades so keep those as far from the camera as you can and because of the pressure keep the holes in the blockade small at the bottom and larger at the top. Just like the examples shown to you (7)

I hope this helps or just give you a different idea on how to achieve a fine river motion

I forgot the picture

/Hudson

Edited July 3, 2013 by Hudson

[hatrick]

Hi Hudson,

Thanks for you effort ! ... In the mean time i tried a very similar setup and it works fine! Although i'm not shure if the problem could be solved somewhat more efficient by faking the rivers stream and combinig it with a smaler fliparea for the splash. When i sim with 10Million Particles only about 1-2 are visibly affected by the fish movement. I mentioned this thought above but i have no idea if such a setup is possible.

Cheers Lucas

[Hudson]

Hi again,

In that case I would definitely try a different solution as you mention. first of all I would go for a stagnant flip container but a bit larger than the actual splash. Create the splash and some foam just to get the right motion of the river and speed of the particles. Once that is done just make the flip box large enougth to get the main splash. After doing so I would create a geometry wich is the river itself with a "hole" wich the flip-box fits. (OBS, I haven't used the ocean tool in houdini yet so I am not sure about its limitations but I think you could create a flowing river as well if I am not wrong.)

Edited July 3, 2013 by Hudson

[hatrick]

Thanks Hudson,

Some questions:

How would you setup the "right" motion for the foam a.s.o.? fake it with a vel field ?

And more important. I think in 12.5. we can use the built in oceanwave tools to do similar things like using HOT (would be interesting if someone could clarify the difference), but how to blend together bouth parts seamless?

Cheers

Lucas

[Hudson]

np mate!

You could create a larger simulation which you already have done. Manually emitt some foam particles(based on a sphere in the flip box or something) here and there so you can see get a feeling for the fluid speed. Once you think the speed is good enough you could use those particles to advect the vel for the flip in the small flip-box. In the small fluidbox you could put an emitter which emits the same amount of particles that get killed by the other end (the same method you would do for a moving flip-fluid box following a boat). In this case you will have a small flip-box for the splashes and keep the actual speed of the main river you have simulated.

when it comes to create a seamless integration I would say that it requires a lot of testing and also controlling the flip-motion at the corners of your small splash simulation. you basically want those to be nullified at the corners in order to integrate with a surrounding grid.

I wish I could help more but I am still to try a similar set-up

[kleer001]

At that distance you can get away with using the ripple solver for some high resolution ripples. It would have to be a different render layer.

Find my demo scene here at the end of the thread.