Is Particle Fluid Surface SOP not used anymore?

[magneto]

Hi,

 

It seems like the FLIP shelf tools are now using VDB From Particle Fluid and then convert it to Polygon Soup. Is this better than Particle Fluid Surface SOP?

 

If so, how do you replicate other features like Speed Stretching and Filtering? I imagine Smooth SOP can be used for Filtering but is Speed Stretching not necessary with the VDB approach?

 

It makes it really hard to know the latest established workflows when you watch tutorials because they use older tools so you have no info about how they stack to the new ones.

 

 

Thanks

[Guest tar]

Quite a few people have posted they prefer the ParticleFluidSurfaceSOP and PIC simulations too, over VDB and FLIP.

[edward]

For filtering, you can use the VDB Smooth SDF (make sure you tell the VDB From Particle Fluid to output an SDF).

[magneto]

Thanks Edward, that helps. I just don't know which is the most preferred workflow for FLIP right now. I am not sure if there are FLIP tutorials for H13, but I assume the shelf tools are at least updated to reflect the most recent workflows in Houdini as it evolves?

[bardia]

Speed Stretching in the sense of ParticleFluidSurface (instancing particles along the velocity direction) is not implemented in VDBFromParticleFluid. Some of its effects are replicated by the "Refinement Iterations" where phantom particles are injected between divergent particles while within limits of influence. This however has no effect, say, on an isolated fast-moving droplet (which is simply surfaced as a sphere). There is work underway for more advanced handling of velocity and this should include at least some parallel to speed stretching. Also, some internal filtering will likely be introduced in VDBFromParticleFluid which should be faster and more sensitive (less corrosive) than what is provided by VDBSmoothSDF. Unfortunately, these are not very likely to become available before the next major Houdini release. 

[Guest tar]

FlIp and VDB seem really cool, and like any new technology offer some great advances on the past and some caveats. In the long run they get all the features of the old and no one goes back. 

 

Just like flat screen and crt monitors. At the start, much thinner than Crt but they just didn't reach the quality at the high end, now they are way way better and offer so many new applications. 

[danw]

FLIP fluids are massively powerful, but they're also complicated and require a certain amount of understanding of what's going on beneath the hood to get the most out of.  I've been working with them in various forms for almost 6 years now, and I'm still discovering and learning new tricks daily.

 

For large, high-resolution volumes of water, FLIP is about the only way you can possibly go at the moment.  Pure particle-based fluids scale too badly as you increase the particle count.

VDB meshing is also far-and-away the most effective way I've come across to convert tens-of-millions of particles into a decent mesh in a short amount of time, but VDBs also have their fair share of complexity, and unlike everything else in Houdini, their inner workings are hidden away and a little bit black-magic.  I'm still in the early days of a serious love/hate relationship with them... they're powerful to the point of having rapidly become absolutely essential to my workflow, but the moment I try to do anything clever with them, I end up shouting at the monitor :-P