Tutorial, walk through of the new FLIP fluids

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I noticed that the brand new flip fluid setup uses a whole bunch of bright and shiny stuff. But how do I use it? What are the pit falls? What are its strengths and weaknesses? What's the overhead on all the vdb stuff? Is there a time where it's better to use the old work flow? Why is there a separate particle_fluid_interior node? Are there other non obvious changes under the hood?

“If you can eat it raw you can't under cook it”
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New from what? From 12 I guess there isn't that big of a difference, except meshing is done with VDB (it's faster) and new tools for whitewater/mist. From 11 I wouldn't know.

If you are new to FLIP, watch the waterfall tutorial from SESI, it's a great start and all of it pretty much still applies in 12.5. Except maybe for the whitewater part, where it is now much easier to get started with the shelf tool.

I don't know what you mean by the “old” workflow, but just try and see what works best for you? That's what it's all about really.

The separate fluid_interior node is so that you can easily shade and render, well yeah, the interior of the liquid.

To be honest it doesn't sound like you have even touched it yet, and your question is so unspecific I don't really know what to answer. Watch the tutorial and play around a bit I say, it's actually quite straightforward.
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Good questions, kleer001 - I haven't had time to look into 12.5's FLIP enhancements yet and I've been wondering similar things myself.

New bells and whistles are nice, but production schedules rarely allow you the luxury of time to play around with them in order to determine whether it's worth upgrading and overhauling your existing setups. Even then, how to go about doing that when your shot is already half-finished and deadlines are looming is another unknown that needs to be resolved before the shot can progress.

Transition guides for overhauled features and workflows would be invaluable for artists that need to hit the ground running with new features rather than burn through dev time they may not have.

Lacking that, feedback from the experiences of helpful pros on the SideFX forums who may have already made the transition are the next best resource for an informed opinion on the matter.
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Thank you rweston, that was exactly the situation. It feels so good to be understood. Under production pressures even the slightest change in technique can be like hitting a speed bump at 200Kmh.

I had just finished 9 months working with the plain old particle fluid surface node Flip workflow at one movie studio. Stuff looked great, it was fast, I knew what I was doing, and I could hit notes. Then, last week at a different studio, a tv shop, I opened up the Flip workflow, that turned out to be a can of worms. And me with a super tight deadline (4 days for 4 shots instead of 4 weeks or 4 months). I freaked out and did the best I could, but I felt like I was missing something important and wasting time unnecessarily.

I felt a little betrayed by SideFX, but I know that this is how software works. When you stay on the bleeding edge of technology you get new toys from super smart people with the best intentions and very little documentation. Why? Because documentation is difficult and time consuming, and overall very boring to produce. And this doesn't just happen with Houdini, this happens everywhere with all maintained software. This happens with Microsoft, Apple, HP, IBM (well, maybe not IBM so much, but that's a different story), but the list goes on and on. The more niche the software, the more earthshaking changes can sneak in.

That's it, rant off.

Well, that and I don't want to do all my flip fluid manipulation in VEX. One of the main reasons I left Maya is that I had to do so much $&#%! hand coding to get particles to behave like I wanted, and I hated it.
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Can you confirm that you were using Houdini 11 here: “plain old particle fluid surface node Flip workflow”? If so, the reason they ditched the popnet is simple: it's slow, and the “ease of use” was not worth it. You can always add a popnet back in if that's what you want to use. For emission, like pyro, they switched to a more sops based workflow, where you build your volumes and points in sops, then source them in the dop network. The new sourcing workflow is great, and a huge improvement over what they had in h11. Peter Quint has some videos on vimeo going over the pyro stuff in Houdini 12 that should get you up to speed (the same nodes are used for flip).

So, for flip, instead of popnets, it's better to use a sop solver with vops or to use fields to direct your simulations. It's faster, and just as versatile, albeit a bit more manual work the first time you go through it. You can use shelf tools for the majority of the work you'll do, and then you can tweak as needed. I never have to use vex (by typing) and usually stick with vops when I need, and if it's something useful, I'll save a preset or otl out of it. I'll also use nodes like gas linear combination if I need to mix fields, but you can also use it on geometry attributes too.

The difference between 11 and 12 was big, but between 12 and 12.5 it was pretty minimal in terms of the workflow. The meshing is different (openvdb) and not mentioned in the docs anywhere, but that's about it, and the particle fluid surface node is still there (and much faster), so you can always use that too. As for docs, I think these all do a pretty good job…

http://www.sidefx.com/docs/houdini12.0/dyno/liquids [sidefx.com] see “Particle fluid networks” – this is basically what I described above.

http://www.sidefx.com/docs/houdini12.5/dyno/liquids [sidefx.com] << I think the page is identical for 12.5

http://www.sidefx.com/docs/houdini12.5/shelf/wavetank [sidefx.com] << specifically has Understanding the network of nodes, which mentions the fluidtank_interior node.
Ian Farnsworth
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Hi guys, I hope you guys will still see my question:

I have been watching the Waterfall tutorial a bunch of times,

and concercing the whitewater creation in the tutorial is so much

complicated for me.

with the new whitewater self, in Houdini 12.5 this would be just a question

of click and connect nodes and voila?

cause I found too much difficult understand how it works in the waterfall tutorial…


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^ Yeah, the whitewater shelf tool makes it all much easier to do now. It essentially sets up a lot of the things they mention in that video.
Ian Farnsworth
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Thanx Ian for your fast reply!

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I am still a bit confused about the white water…

if someone see any files or new tutorials about the use of it (houdini 12.5)

please let me know!

thanx in advance

Ronaldo
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