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Found 567 results

  1. 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!
  2. 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
  3. 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.
  4. 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!
  5. 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.
  6. 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!
  7. 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.
  8. 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
  9. 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
  10. 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!
  11. 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
  12. 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
  13. 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
  14. 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
  15. 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!
  16. 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
  17. 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.
  18. 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?
  19. 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
  20. I have a FLIP tank with some action going on. It's just someone diving, so the part of the tank that requires a lot of computation is small, but it's an underwater camera, so with a small tank you see the edges of the simulation. Is there a way to either focus the simmable area in a tank/make particle separation dramatically smaller in one area, to accommodate a huge tank with not much going on so the render times aren't crippling? I've seen tutorials on using lo-res sims to drive hi-res, but that is sort of the opposite of what I'm looking for. I've also seen some endless ocean tuts, but since what I need is an underwater dive, and the breaking of the surface (and the water still beforehand), I haven't found a way to make that work. Thanks for any help!
  21. Whitewater h17.5 Not to emit bubbles

    Hello, Using Houdini 17.5 to create boat wake with white water. Using the white water solver I where I would like to emit foam and spray over the flip surface. However, I do not want the bubbles as I am under the impression this would reduce simulation time and memory consumption. That said, I couldn't figure out a way to stop the solver from emitting bubbles! Anyone was able to deal with this or any documentation or thread that could help?
  22. Freeze Flip Sim

    Hey Guys, Imagine an object which fills with liquid over time. When the object is full of liquid i want the motion of the Flip Fluid stop oder decrease over time. For example: - Object fills with Flip Fluid from Frame 1 to Frame 96. - Liquid and all motion of it slows down from Frame 96 to Frame 144, at Frame 144 everything is not moving anymore. I tried some pop wrangle inside my DOP but i cant get this working. Any suggestions? Should i do this after the DOP in SOP Level in a Vop/Wrangle or could I achive this inside my DOP? And How? Thanks and Greets, me
  23. Hi! I have what is probably a dumb/obvious question. I have a character diving into a pool. He is modeled to scale (roughly two units high), but to get the details of a human diving I'm having to make the collision separation and particle separation very small. The problem is that this is a huge body of water, and the camera is underwater, so the tank can't be isolated to the area of activity or the "walls" of the liquid show. I don't need detailed animation/simulation outside of the area around the diver, just some turbulence to make things interesting. Is there a way I could focus particle density around the area where I need the detail? Can I nest one sim inside another? (The places I've seen one sim driving another have seemed to focus on up-res-ing, and it doesn't seem to fit what I'm doing here.) Or do I just deal with the fact that a large body of water, even if there is not much happening, requires a ton of sim-time? Thank you for your help!
  24. I'm looking to find a way to make a FLIP fluid sim move particles, which would themselves be used to instance underwater particulate matter or bubbles. All of my Googling turns up ways to make POPs influence FLIPs, but I'm unable to find this, and I'm sure it's depressingly easy. The scene is a pre-animated character diving into water. To get the bubbles as he dives it looks like the best bet will be to emit particles with instanced geo bubbles (correct? No matter how splashy I make the sim, I'm not getting any bubbles happening from the dive itself). Thanks for any help!
  25. Good afternoon guys, I'm trying to create a setup similar to the one below. Where the drops are with dynamics and glued to the surface. Does anyone have any tips on how to start this game?
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