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Zybrand last won the day on April 8 2019

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  1. Thanks for the plug @Librarian . I should probably make a post on here telling people about them since I have been doing to for a while now. @Pj20 to me your reference looks like pyro flowing around a sphere and particles being adverted through it. My tutorial is a little different but maybe you can borrow some ideas from there: https://vimeo.com/531163248
  2. I also thought it would behaved like that but it seems like it's setup so that ambient temperature = 0 buoyancy. I think sparse pyro needs a masterclass.
  3. Hi Terry, Do you have an example of what you are trying to make? Yeah the focus of that tutorial was about meshing. The nature of those constraints means that as soon as they can they will snap back to their @restlength distance. You can update the restlength as they stretch but you will have to store an extra initial rest length attribute to compare against. Also updating the restlength will affect strain which is tested for breaking constraints so if it rest length grows you constraints might not break. So you might have to setup a custom constraint breaking setup or trick the solver some other way. I hacky way to slow the snapping back to rest down is using acceleration limit and a speed limit and a bit of velocity blending. If you have access to vellum I think you have a better chance of controlling that motion if you move your setup over there as there are more controls you can use than with grains. Have a look at the hip file attached setting a high damping ratio help slowing the constraint down after they break. hope that helps. zj_vellum_grain_damping_ratio.hiplc
  4. Hey Jack, well the answer is in the name of your hip file. Like in your emission you need to run the point deform through a foreach just make sure your grains inherit the piece number. Check out the hip file foreach_zj.hipnc
  5. Hi BiZz, Vellum constraints can be very tricky and you can run into all sorts of problems setting up custom ones outside of the vellum constraint nodes when you are in DOPs. I gave you problem a go myself using a couple of wrangles and I managed to get a stable result working. For a longer explanation and a hip file is on my blog: https://zybrand.xyz/vellumcontinuous-emit-with-dynamic-constraints#more-324
  6. I didn't consider having both the thin and thick tube looking the same with the same setting and just switching. I expect them to need different setting to behave in a similar way because of their shape differences and the point thickness changing between the two shape, if they were behaving the same I would be disappointed in the vellum solver. If you want to switch between them without adjusting cloth and strut settings your best bet is probably to multiply the stiffness parameters with attributes on the geometry. Maybe calculate the the area of the shapes or something similar and multiply the stiffness by that.
  7. I think there are a couple of things going on the effects your sim results. Because you thin shape is so much thinner that the thick shape your point thickness changes which will effect the sim, if you visualize thickness in the sim you will see that changing between sims because of overlap. Then the bigger difference between the width and height of the primitives of the thin tube will make it bend easier and that has more to do with the cloth settings than the struts. Increasing the stiffness and bend stiffness a lot on the cloth constraints help as much if not more that the struts. I also upped the strut constraints stiffness a bit. Making those changes gives you good results while only having to set the solver substeps to 2 and the constraint iterations to 200. So you can avoid 4000 iterations odforce_example_zj.hiplc
  8. Hi Zinogino, What you are trying to do will never work. The fluid mesh is an arbitrary mesh and the point numbers will be in different and in different places every frame, as far as Houdini is concerned it might as well be completely different shapes so there is nothing to interpolate. That is why you have to transfer velocity from points as well. If you want to retime the simulation you will have to do it before you mesh the fluid. Hope that helps. Z
  9. Collapsing to a material instead of a sub-net did the job thanks
  10. Hey guys, I am having trouble converting a SHOP setup to the MAT network. I am sampling colours from a cached point cloud to change the surface colour and it works as expected in the SHOP network if I promote the pcopen file and pick a sequence. But it doesn't work in the MAT network, if I leave it as a flat network there is no where to promote to and I get the "time dependent warning" and putting the setup in a subnet and promote that still doesn't work. I either get the first frame of the cache sampled or nothing at all. Is it because the MAT network is just a massive VOP? And is there another workaround? thanks, Z
  11. Also grain has a built in speed and acceleration limit you can use. And uping the drift threshold might help with you sim as well.
  12. Have you tried using surface tension?
  13. OK that is fair enough, I thought you were saying that you were researching beer specifically for a long time. I used Realflow before I moved to Houdini haven't used it in a long time though but its SPH liquids are probably better for beer than FLIP. But since this is a Houdini forum I'll stop talking about other software. A good place to start would probably be variable density with using density by attribute in the FLIP solver. Or you could do the foam as a secondary sim after the initial flip sim. simple_beer_zj.hip
  14. If there is almost no info how have you been researching this area for a long time? To answer the why no tutorials question, my best guess it that traditionally the strength of FLIP fluids is in doing large scale water simulations and it is easier to do out of the box. Apart from more viscous small scale simulations large water sims is what more people use it for equaling more large scale sim and more large scale sim tutorials. Surface tension out of the box for example is a new feature so you won't have much tutorials on it. I am not saying you can't do good small scale fluid like a glass of beer, you can for sure. Its just that the main focus of the community has been geared more towards large scale ocean sim.
  15. Hi Phiphat, Sounds like you narrowed down your problem to the "Flatten Geometry" section of the Particle Fluid Surface. You mention that the problem happens at different frames with different particle separation values but does it consistently happen at the same frames at the same resolution? If so that eliminates any sort of ram limit issue. If you dive inside the Particle Fluid Surface you will find a FLATTEN subnet which handles the bounding box and flatten geometry calculations. In there VBDs are being edited and merged together with a VDB combine using SDF difference and another using SDF union. That is most likely with your problem is because it looks like on of those VDBs are being calculated wrong and subtracting the whole fluid surface on those frames. The simplest thing to try first is just to adjust your bounding box size and see if the problem persists.
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