How to affect a fluid stream dynamically from a curve?

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I'm trying to create this effect in Houdini like it appears in this video at the 1 minute and 18 second mark:



I'm a bit stuck and I wonder if someone had a better approach to tackle this than what I tried which is to have a POPSource into a POPSolver and then use the POPCurveForce to get my stream to follow along a curve path.

So far my results are less than stellar and I'm hitting a bit of a wall.

What I'm trying to create is an effect similar to this stream of water. Ultimately it will be animated from one straight curve to a spiral-like curve to the beat of music similar to what is in the video.

Any help would be massively appreciated!



Edited by Midphase - April 12, 2023 18:49:18

Attachments:
Screen Shot 2023-04-12 at 3.25.32 PM.png (602.7 KB)
Screen Shot 2023-04-12 at 3.25.41 PM.png (513.8 KB)

>>Kays
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Make fluid fallow Path use (from imaginary Source Speakers Spiral to make Volume trail for use in Fluids source Scalar Filed Mask to make Control only when passing thru) use chops to manipulate just one point(spiral in your case) or more depending what Freq you want use in Sound)

or Cheat (use Spiral from Labs )activate vdb and use to make filed vel),it's Fast. you have Files on Odforce Forum posted long Time Ago (USer Librarian) ..Have FUn
Edited by cncverkstad - April 13, 2023 12:49:50

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sdaaa.jpg (677.7 KB)
tr.gif (648.6 KB)
tg6.jpg (231.0 KB)
spral.jpg (413.3 KB)
sprald.jpg (133.7 KB)
tr11.gif (631.7 KB)

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Since the spiral is so well defined in the reference, the easiest way to go would probably to go with simulating a simple straight falling down liquid stream. Then make a line (line SOP) along that curve and resample it for some more detail, use the point-deform node and capture the liquid stream with the line, now you can just twist and bend the line that acts as a lattice for the liquid stream you have. This will be fast, easy to manipulate and you can still use CHOPS to deform the line if you really want to get it to be audio-reactive The other option is to actually deform the liquid with forces, but you will end up needing a lot of iterations to get the forces just right... So if you have the time you can push for that little extra dynamic, if not, go the easy route. Cheers!
Edited by Robbert - April 13, 2023 09:17:45
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Thank you Robbert, yeah actually I hadn't thought of the point-deform node, but I think that might be my best bet. I have been fighting with the POPCurveForce in my FLIP sim all day yesterday and the moment I activate the curve all my liquid goes flying all over the place before it settles into the spiral. The shot that I need is about 3-4 seconds so I need the liquid to take the shape immediately as if manipulated by invisible forces.

I'll give that a try today!
>>Kays
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https://www.youtube.com/c/RightBrainedTutorials [www.youtube.com]
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Just a quick update for anyone interested.

Basically I was able to use the POPCurveForce to get my FLIP sim to follow a spiral curve. Animating the POPCurveForce results in a mess before the effect settles into a nice spiral which won't work with the beats of the music that need to be immediate.

I tried using the Point Deform SOP and wasn't able to make it work whatsoever, it results in a mess of polygons that looks terrible -- probably user error but ultimately I gave up on it.

The best solution I could come up with at the moment was to take the Alembic of the plain simulation into Blender where I'm using a Lattice Modifier that allows me to shape the fluid stream into a spiral that I can then animate to the beat quite easily. I was hoping for something a tad more sophisticated than that, but I'm running out of time.

Once again I feel like Houdini is great at the complicated stuff, and terrible at the relatively simple stuff.

If anyone has a better solution please let me know!

Attachments:
Screen Shot 2023-04-16 at 9.26.16 AM.png (2.2 MB)

>>Kays
For my Houdini tutorials and more visit:
https://www.youtube.com/c/RightBrainedTutorials [www.youtube.com]
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I did something similar some time ago, which is why I proposed this solution in the first place. Worked out for me so I can probably update you with a bit of my setup in the coming days. For what I can say now is that I just simulated a water stream pouring straight down (using a POP advect by Volumes to keep it tight, but you can use whatever you prefer) and then post-sim point-deformed it with a point-deform node piping in the FLIP-sim a staight sweeped curve, and a deformed sweeped curve (deform the points, not the mesh, only re-mesh it after deforming). Simple as that, It will work
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Thank you, yes I'd love more details on your set up or even a .hip file if you're willing to share.
>>Kays
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I had to deconstruct this setup a bit from a much larger setup, so there might be some things that you simply do not need or things that can be simplified for your setup. But it might help you get going. There is basically a curve that you can sculpt however that will guide everything down the line. The sim is extremely simple and fast, in another version of that setup I also transferred the f@curveu from the original curve to lerp attributes down the line (confinement of the shape for example). There are some operations in the last step to control the confinement of the shape and such, as the original setup was used to go from a water-like shape into a perfectly glass-like shape that still had to retain the bubbles moving through it (so we needed the flip particles in there).

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simpleflipcurve.hip (1.0 MB)

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Here's maybe another way of tackling this, which is not using simulation at all but utilizing some noisy displacment and a path deformer.
Edited by Yader - April 19, 2023 12:36:01

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flipbook.mp4 (162.3 KB)
Fluid_Flow_Spiral_03.hiplc (352.5 KB)
houdini_5gSzmMOuae.png (1.5 MB)

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Thank you so much to both of you!
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For this type of effect, I don't think you need FLIP, I tend to just animate points along a spline by offsetting the UVs of the spline, add in some noise, and voila.

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particles_along_spline.hiplc (536.1 KB)
points_along_spline.png (342.8 KB)

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