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Found 499 results

  1. Paint splash

    Hi guys, Im really in need of some help here. Im trying to find a way to paint a mesh using flip fluids. The idea was to have an alpha of where the fluids collide with the mesh to then use in compositing to reveal a texture. However ive been lookin everywhere an cant seem to find how to extract this information. Here is an example of its use in substance painter Thanks for your help guys,
  2. If you're flip simulation flickers from using reseeding particles this threads for you. TLDR: I've found a temp solution but want a better one. Inside the flip solver search for a node called "Gas Seed Markers"(Its renamed to "Reseed Particles") Uncheck the "Build Inside Surfels". This will stop the popping but maintain the effect of deleting the unnecessarily dense overlapping particles. Starting this thread for myself to document my thoughts on this but also for anyone else who needs reseeding to keep their simulation in check. So far I have a temporary solution to my issue but I want a better one. My hope is that we can discuss a better means of achieving the desired result of consistent fluid particle density without flicker or popping. The masterclass doesn't explain reseeding and I couldn't find much on the topic in forums or elsewhere for how it works. The node responsible is Gas Seed Markers(GSM form now on). It checks the number of particles per voxel within the surface field for inside the fluid and outside within a given number of boundary voxels and does three things. A. When particles exceed the desired density per voxel GSM will cull the points of that voxel. B. If voxels beneath the surface do not have the correct density GSM will add points. C. If there are not enough particles on the surface, within 2-3 voxels GSM will fill that voxel with the desired number of points per voxel. It seems on one frame the GSM node will delete ALL particles within a voxel that exceeds the limit. Then the next frame, because the void was created it will then repopulate the void with the desired density. So this is where I'm hoping for some help in understanding, in order it's: 1. GSM determines particles are too dense. 2. GSM deletes all particles in voxel. 3. Complete solve (particles partially close in on this void) 4. Next Frame of solver - void still exists so GSM adds particles to this voxel with points = Flicker / Pop. So to start the thread: First - Does Gas Seed Marker delete all particles within a voxel that exceeds the density limit or is this an optical illusion? Second - I'm having trouble getting this node to function outside the context of the flip solver. I want to see it populate points into the Geometry data but it has a lot of requirements regarding the slice index that I don't fully understand. If anyone has or can create a working example of this node functioning outside the context of the flip solver I would greatly appreciate it. For now I'm going to try using two GSM nodes one after the other. The first only performs the cull operation and the second performs the fill before processing the solve. Will post back with results shortly.
  3. create flip tank inside object

    hey there, im newbie to houdini and here. Im trying to achieve fluid in bathtub, easiest way seems like using flip tanks. But i don't know how to do that with custom shape instead of box. Also i will add some rigid bodies top of that water later. Also i tried to fill it with particle emitters but i couldn't success. Also how i freeze it after it fills, initial state ? In short: bathtub with water, floating rubber duck and some other model in surface. attached scene file. bath.hip
  4. Hi, I am summoning all of you flip gods! In the images you can see the flip explodes upwards for no apparent reason, this seems to happen along the boundary of the collision object. I am using guided ocean layer setup. The collisions otherwise behave correctly. I have tried high res sim, low res sim, changing grid resolution, changing collision geometry (submarine model, simple scaled sphere), deforming collision geometry, object transform collision geometry, zeroing out collisiovel field, high resolution collision vdb, low resolution vdb, playing around with depth of the guided ocean layer, different amount of substeps(both flip solver and autodop), reseeding settings, changing integrator types in the flip solver and probably more... Quite frankly I am at my wits end and I wonder if anyone has ever seen this kind of a problem and if there is a solution to it. I would also like to avoid making the boundary layer exceedingly deep, as this would most likely kill all the detail. I have attached a simplified hip file where this problem occurs. Thank you exploding_water_problem_v1.hip
  5. (I'm not good at English) I wonder How to I delete the particle from collision boundary. according to the Kill Inside Collision is Delete any particles inside any collision objects plugged into the second input. flattank size equal bounding box group to create .. um.. I need solution and vex sentence. Would you explain this ?!
  6. Ocean Ship Sails

    Hello there! I'm trying to create a ship sailing effect on Houdini 17.5 (with Guided Ocean Layer tool). But I'm having lot of issue. - First of all, as you can see on flipbook, I have lot of particles popping up from ship sides. Why it happens? Can't figure out how avoid this problem. - I used the Deforming Object shelf tool for simulating the ship as volume source. However if I choose Volume as Velocity Type on Flip Solver > Volume Motion > Collisions tab, it looks like fluid doesn't interact well with my geo. Basically I have not splashes, even if I select "Use Volume Velocity for Collision" on Flip Object > Collisions. So I need to switch on Point velocity Type in order for me to have good results. Is that a correct way even if my collision source is a Volume? Is it better to treat collision geometry as volume or mesh? - Is there a way to avoid splashes to slide on surface? I tried to increase the Velocity Blend (on Flip Solver > Particles Motion > Droplets) with no results. - Lastly, I'd like to achieve a good results regarding wave trails (see pictures). Basically I have too rounded and large waves from the ship prow. I'd live to have more V Shaped waves. My scene is more or less in real scale (meters). I used a 0.8 Time Scale value in FLIP Solver in order for me to have good trails, but cannot achieve the desired result. Any help will be really appreciated. Thank you so much for your time. Ship02_Sail_v06.mov Ship_03.hip Ship_Body.obj
  7. Simulating flip from bottle

    Hello everyone. Long time since last post here when i was dealing with the same thing. After watching some tutorials and learning some more in houdini i decided it was time to go back and see if i could get some better results. There is still some big questionmarks that im seeking answers for. Here goes. This is the simulation i want to do. Animating a beer bottle (prefferable in maya since i have a rigged character and i have made a animation that matches footage so i know that the animation is timed correctly and so on. The bottle will be pouring beer into a pretty standard glass. When i have a stable flipsim i would want to go on and simulating bubbles and foam. So on to the questions. 1. I have noticed some differences between using collision geometry made in houdini or imported geometry. Making the geometry in houdini seems to work much better for some strange reason. Can anyone confirm this? It seems that i get away with much higher settings on particle separation and gridscale then using similar objects imported from maya. 2. Scale seems very important here. Simulating in real scale gives a lot of trouble. therefor i scaled the bottle up so that it is around 1 meter high. However, this gives some problems when it comes to actually using the animation i made in maya. Everything in maya is done in centimeters and when importing it to houdini its way to big. I ended up matching the animation inside houdini from the imported file and used that instead. Wich is the best way to get around this? Usually in production everything is modeled in correct scale in maya. 3. Setting up the flip source. Is this the correct way? Import the fbx file with the bottle. --> create a new geo node --> create a box big enough to cover the bottle and up to the level where the liquid should end at the bottleneck. Object merge the bottle into this geo and connecting a boolean with subtract b-a settings. Then i blast the exterior so i have only the interior of the box minus the bottle. 4. In the bottle geo i have a transform and after that a null. i put the displayflag on the null and then create a deforming object from that. 5. finally i create a static object from the imported glass. Now all is setup to start simulating. ofcourse there is alot of tweaking of particle separation and collision settings to be done but overall is this a good setup? I can post a file if that helps. Finally some other questions. When caching out the flip to simfiles i only want the particles to be cached. where do i set this up? Regarding substeps, if i raise the substeps INSIDE the dopnet on the flipsolver will this generate more substeps when caching it out or is it only the substes on the dopnode that sets substeps in caches? Sorry for kinda of a long post but if anything can be answered i would be grateful! THX!
  8. Divergence Problem

    Hi Guys. I'm trying to create a kind of 'expanding foam' effect (like an Elephant's Toothpaste chemical reaction). Expanding out of a teacup. But my FLIP fluid is hitting a weird shelf and not overflowing the edges of the cup properly (see below). My emitter is a sphere at the bottom of the cup. .hiplc file also attached. Any pointers hugely appreciated. Elephant_Foam_02.hiplc
  9. I am working on a shot where a very viscous fluid hits a character. Everything is working great on the sim and giving me look I need, but I was wondering if I could add a "stretch limit" to it somehow. Like "if it stretches by x amount, break it up into smaller pieces" without losing the viscosity much or getting it back after the breakup. I am not sure what attribute I could reference for that (if there is one). Help me odforce, you're my only hope.
  10. Grouping points in cached FLIP sim?

    I have a pre-simmed/cached FLIP sim. I would like to create a group of a section of the particles of the sim so I can mesh them separately and apply different shaders to them later. Re-simming is difficult and slightly impractical, so I would love to be able to do this with the cached points as-is(/are). I can create a group of points, but it looks like point numbers are not constant in FLIP sims, as the group changes over the course of the sim (frame to frame, actually). Is there a way to create a group that then remains constant and flows with the existing sim? Or even a way to create a new group of particles that is advected by the existing cached sim? (I'm pretty sure it's no longer a "volume" by then, so I'm guessing a straightforward advection by volume POP wouldn't work.) Or a way to do some sort of "sort" operation to compel points to retain point numbers, which I could then group? Or advecting another form to follow the sim, and I could then use that as a bounding volume to create my group? (Point deforms with FLIP sims as the deformer seem to get really messy really quickly.) Thanks for any help!
  11. FLIP VORTEX SIMULATION

    Hi, I'm doing a project for a short film; and I am trying to create a water vortex. I looked into a few resources creating custom vector sources etc but I realised that I am having trouble using my custom vector source to drive a (basic) FLIP simulation. Do you have any alternative ideas that I could explore? Cheers.
  12. Flyaway particles in viscous FLIP

    I'm running a FLIP sim that I would like to make fairly viscous (read: blood from a wound). If I crank the viscosity high (2500 - 5000) I can see some general slowdown, but the problem is I still get lots of little flyaway particles and after meshing the result still looks very particle-y. I've toyed with surface tension, but have found that it either makes no apparent difference or it just makes the sim explode. Any idea on how I can make my viscous fluid more "stringy"/viscous? The emitter is very small as the scene is fairly small--I actually had to scale up the imported alembics so that the character's head is about a meter high, as "real life" size was too tiny for me to get anything useful out of FLIP. I'm testing at a particle separation of 0.002, doing more detailed tests at 0.0005. Could it just be a matter of cranking those down to ridiculous sim times for it to look less like popcorn? (Unfortunately posting the file isn't do-able, any more info needed I'm happy to supply.) Boosting reseeding to oversampling 48/bandwidth 3 seems to help with the overall feel, but just delays the flyaways, doesn't eliminate them. Thanks for any help!
  13. Hi guys, I made this simple sim in Houdini and exported it to C4D to render with Octane V4 as alembic. The problem is that in the first frames, there are those weird polygons on the mesh, maybe normal problems? I didn't manage to fix it so I'm ask if anyone here had this problem before and knows a solution for it. I will attach the render and my hip filie below. Thanks in advance. RnD_Viscous.v0.hip lan_rnd_sorvete.mov Edit: I'm sorry admin I messed up with the replies.
  14. Need help with tear drop flip sim

    Hey guys. I'm pretty new into Houdini and I need to create a flip sim of a tear drop falling off an eye. I tried to play with Surface Tension but I didn't get any good results. Does anyone have an ideia on how can I make this sim? Thanks in advance
  15. I have a meshed FLIP sim (cached out, .bgeo files read back in) that I want to use as a "solid" object and have a rigid body rest on top of it (the idea is that something solid "ripples" psychedelically and the objects resting on top of it move as the ripples go underneath--but the original object is still a solid, and the objects don't sink into it). I just can't get it to hold up, however--when the RBD object is initially "dropped" onto the fluid mesh, it bounces and settles as expected, and does okay with simple early movement, but eventually the collisions become less and less precise and the RBD object just sort of sinks in. How can I get the mesh to read as just a run-of-the-mill deforming object? I've tried RBD solver, bullet solver (obviously doesn't work with the shape of the mesh), volume and surface collisions, jacking up collider volume resolution to make sure all the little waves are getting captured, and boosting the substeps, but the result has been pretty consistent (except more substeps = super jittery RBD as it's reading all of the little pre-big-movement mesh ripples). On the attached setup (a simpler version of the project giving me trouble) I even ran the meshed surface through a "clean" just in case any of the lingering velocity attributes were throwing it off, but that didn't help either. I'm wondering if the fact that the topology itself changes so much might be the problem, but if so I'm not sure how to fix that. Thanks for any suggestions! flipmeshtest.mp4 meshtest.hiplc
  16. I'm trying to create a custom velocity field for a FLIP tank (so I can "pin" part of it down with 0 velocity, while part of it sims all over the place). I'm following this tutorial: https://www.youtube.com/watch?v=xm404aavXrY --but it's from a version or two ago, and when he brings in the volume he created with the velocity attributes into his DOP network, he uses "source volume" and brings in the fields via SOP to DOP bindings (at about 12' into the video). I've crudely sussed out how to use a Volume VOP in the bit where the volume is created to add noise, but not how I could add the velocity at that level (if in fact that's how it's done). Following this model: https://www.youtube.com/watch?v=8UaDetbvMAs I have had success--grouping the FLIP particles in a SOP Solver and using a wrangle to set a custom velocity--but to my knowledge doing it that way won't produce a falloff--it's a very clear line in the tank between the 0-velocity particles and the non-custom particles. Thanks for any help!
  17. Flip Fluid not filling container

    Hey all, I am relatively inexperienced with Houdini and very new to Flip Fluids and having some issues with my simulation. So I have created a container, which I would like to fill with a fluid. I am trying to make it so that the fluid flows into the container and half way down interacts with some text. For this I have placed a static object around a particle emitter and the text is also a static object. While the fluid does flow the particles emitted disappear and so the container doesnt fill. I tried to mitigate this by using a larger particle emitter source but this hasnt really worked. Any one have any suggestions as to how I can make this container fill. I would also like to slow down the velocity of the flow and increase viscosity if anyone could help that would be great. Cheers Alex 190903_Animated_Logo.hipnc
  18. Flip Sphere Motions

    Hey there, I'm trying to replicate this setup: Liquid Sphere Based on my scene, I have a sphere and the particles are generated from it with iso offset and particles from volume. Within FLIP, I tried to control the velocity with pop forces (POP force, pop attractor and pop axis force) and got somewhat of a swirly motion but the in the reference video, towards the end you can see the fluid is ground around a torus like motion and the shape as well Any pointers on achieving this? HIP file attached included. Thanks! SH02_Water_v02.hip
  19. Flip Fluids deforming collision objects

    So I am quite new to Houdini, I have a fairly simple setup where I am simulating the behavior of a viscous material where viscosity is increasing exponentially with age and multiplier. So by frame 120 particles stop moving. I am emitting in a line in a loop back and forth so slowly the particles start creating a layered wall. However I have encountered 3 very intriguing problems which for the world in me I cannot seam to figure out: 1 - When meshing the particle data the particles that are close get meshed (obviously) and I don't really see the layering that I need to. Tried creating a very highrez model but didn't really work. (Is there a way to use the viscosity or age variable to stop particles from meshing together and keep the layering intact?) Currently using VDB from Poligons then converting it. 2 - Despite a very high Viscosity, the particles move somewhat when new layer of particle is added on top. Is there anything like Pop-State (as in previous releases) where I can freeze the particles with attributes? currently using (if viscosity>100000 {v = 0,0,0) to set velocity to 0 once viscosity is high enough. 3 - If I wanted to use a deformable (cloth/plastic/elastic) object to fill the flip fluid into how can I go about this? I hope some of you brilliant houdini artists have some advice or tips on how to go about solving these problems. Houdini file attached. SimCon1.hip
  20. Pro tips for flip meshing?

    Hey guys, I have a little question regarding flip meshing. I'm trying to do some studies using the Particle Fluid Surface node for my final mesh, but I'm feeling something is a little bit off in my results Dunno if it's just the lack of refraction and shading, but my mesh seems a little blobby. I already tried to play with Voxel Scale, Influence Scale, and Droplet Scale, but in the end, it still a little blobby to me My flip sim is ok, good resolution, billions of particles and stuff. Any pro tips? PS: I've already tried the filtering options, masking, etc My mesh Same sim, but only points
  21. How would one increase FLIP viscosity based on particle age, to get a thickening/coagulating effect? My searching only found one how-to from 2012, which doesn't work in H17+. I understand setting viscosity by attribute, but it appears FLIP particles don't have an age attribute, so I'm not sure how to shoehorn one in there. Thanks!
  22. Hero Object rest force in flip

    Hi everyone, I got a flip sim with a hero object Floating on top of it. Now I want to make sure, the object floats but kinda stays on a specific spot. So I used the rest Attribute and subtracted to Position from it (in the dop net). If the distance is getting bigger the force should increase as well. Unfortunately the force is pulling the object to the Center of the Scene. Maybe any quick solution for that? Added a supe rsimple hip file heroforce.hiplc
  23. Hi, I'm struggling with an issue I have at the moment where I have a boat that floats along an ocean surface which follows a curve. The idea is to have a path and an ocean I can evaluate and have a boat bob to the waves (I've done this part) and have a guided ocean simulation follow along with the boat. I've then taken the normal and the up vector and used trigonometry, one unit length circle and vex to create Y rotational data. Then by diving into the ocean source node and applying this to ocean evaluate and boundaries with out interfioring with the ocean spectrum I end up with a rectangular particle source that rotates with the boat allowing me to have a smaller source of particles (instead of a large square centred on the boat) that highlight the back and side of the water next to the boat. My problem from here is the flip fluid solver only takes the centre and size from the ocean source, held inside gas resize fluid dynamic nodes of the flip solver. This gives my fluid simulation an incorrect result. I'd like to be able to apply the rotational values to the flipsolver using position, object position, motion node or anything else that would work. However upon facing this problem I've realised my knowledge in dops is extremely lacking and I'm confronted with green and purple outputs of nodes that don't like working together. I have a feeling this is possible due gas resize nodes ability to rotate for clustering and other pyro Sims, I just have no idea how. Can post my hip when I'm back from work later today, if you have any questions please ask.
  24. FLIP colliders flickering

    So after a very lengthy FLIP sim I'm finding that my colliders are arbitrarily flickering in and out and disappearing altogether. I had done various tests--this happened a lot with lower res settings but seemed to stabilize at the final sim resolution--until frame 240 (of 250). The problem appears to be in the static object itself creating the collision geo. It's set to use volume collisions, mode is volume sample, division method by size at 0.005 division size. The object is an animated person at scale (about two units = 2 meters tall), this setting was about as large as I could go and not lose details. The .abc itself is imported and unpacked. The same object is used elsewhere to drive a pyro sim and it's working fine there. How can I ensure that my colliders don't just disappear?
  25. FLIP Divergence

    Hey guys, I'm trying to use divergence with flip but things get kinda unstable. I'm using only the point attribute, should I use a volume field as well somehow? Thx FLIP_Divergence_v0100.hip
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