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Found 73 results

  1. I am trying to make a water tank using FLIP, but I am having collision problems. The tank is hollow inside, I intend to render it as glass, but when the water collides with the surface of the tank it disappears. I have had to use surface collision as opposed to volume because the volume collision does not detect the hollow inside, it simply makes the collision the outer shell of the tank. I have attached a hip file to show what is happening, as well as the obj of the tank. I have tried increasing the collision offset, but it doesn't seem to have any effect, plus I can't go too far with it because it will plug the hole I have in the center. Any help would be greatly appreciated. WaterTankTest.hiplc WaterTank.obj EDIT: I did forget to mention, I am on 16.5.323
  2. Hi Everyone, I am still new to houdini and I frequently run into the following problem. WhenI use VDB volume for collisions in houdini Particle or Flip sim, particles collide with the bound of VDB volume instead of actual VDB shape. It kind of creates a boundary around VDB and uses that boundary for collision. Its visible in the viewport in orange color (yellow color in the provided SS as d object was selected when took SS). I often get this issue and I dont know what I am doing wrong and how to solve it. Even If I use shelf tool the problem still persists. If anyone of you have ran into this problem then please let me know how u solved it. thank you for your time. Cheers!!!
  3. Sticky FLIP on moving Object

    HI everyone! It's my first time here, I hope I'm doing it the right way. I'm practicing in a shot where I have a couple of cherries falling by gravity and hitting each other, releasing some droplets. In order to have the droplets following the surfaces I'm using Stick on Collision in the flip solver collision tab. Unfortunatelly, no matter how much I increase the values in the stick microsolver, the fluid start moving fine but after a few frames It starts getting off the surface. Is there a way to consistently transfer these velocities from the geometry to FLIP? The movie bellow shows what I've got so far. Thanks everyone!!! stiky_FLIP_test.mp4
  4. Flip vs scale vs collision

    Hi people, I want to create a simple apple who drop into a water flip tank. -1 square in Houdini flip is 1 meter so i tried to make a realworld scale apple but it dont work at all my apple bouncing back violently from the water. Any suggestions please ? i tryed to flip sovler -> volume motion -> solver -> feedback scale to 1 but it dont seem to work Houdini 16.5.268
  5. FLIP - Slip on Collision Control Field

    Hey guys, What is the best way to use the slip on collision control field, to avoid viscous fluid of sticking on objects? I managed to do it with the help of a friend, using the gas match field + a source volume. it works fine for static objects but not at all for moving ones. I have a project with an alembic animation and I really need to use it on the animated surface. Can someone help me? Here's the setup in dops: Here's it working fine with a static object. It's a top view and the red box is the sliping object: and here the red box is animated, not working: Not sure if this is the best way to approach it so any other ideas would reeaally help me scene file is attached Cheers, Alvaro flip.slip.v2a.hiplc
  6. Flip Fluid Collision Problems

    Hello! I am having a problem with collision for my flip fluid sim, frame 2 for some reason a chunk of particles falls through the bottom of my "cup" I've checked my collisions on my "cup" and I've also tried adding a sub d node in my tree. both didn't have any result. Also, as the sim continues my particles pretty much all disappear. I'm pretty new to water sims so I'm not really sure the problem. Thanks!
  7. Dealing with FEM + Static Body

    Good night, people: I'm a newbie with Houdini. I've tried lots of tutorials but, I'm still having problems with collisions. I made a simple setup, a growing fem ball inside a static collider, but, it interpenetrates the walls of the static object. I tried to get more substeps, to have more detail in collision guides, but I'm not sure what I'm doing wrong. I attach the file that I'm working on. Thanks! testme.hipnc
  8. Small RBD collision issue

    Hi all, I'm new in RBD and I have this issue. I fill a box with objects instanced by particles. The box is a collider in convex hull (per Set Of Connected Primitives because I splitted all faces of my box) My small RBD objects are in Convex Hull as well because Concave seems to act weird. The problem is the RBD don't stop spining on the collider If anyone has some tips it'll be very appreciated. I joined the scene file because it will be more helpful Thanks a lot ! croquettes_16_debug.hip
  9. FLIP Stick on Mesh

    Hey guys, What is the best way to make FLIP reaaally stick to an object? Right now I'm using only the "Stick on Collision" option but it doesn't work as I expected. I've crancked up the normal value to make it move more drastically but It's getting unstalble. I guess this setup from Dave Stewart works better than the Stick on Collision only (i guess he's using both). It doens't stick like mud the the object but I'd like to know how it works as well, he says: "Grabbed the Pressure field values (Gas Field to Particle) and ran them through a POP VOP, also using the surface distance to reinforce the outer shell of the toy." how can I use the Gas Field to Particle? I know what it does but i have no idea on how to connect it with the object and trasnfer this velocities using a VOP POP. Well, any tips are welcome Thank's - Alvaro
  10. Hi again everyone, I'm working through a Pluralsight tutorial (Introduction to Houdini Pyro) for developing a firebreath sim. It was made in Houdini 15 and I only have access to Houdini 16. I've been running into some issues related to the different versions. One of my main problems at the moment is my pyro sim isn't colliding with the dragon geometry that I need to be using in my current project; there are some minor differences in settings as I need a much smaller flame with a different look, but otherwise I'm following the tutorial's steps closely. The POP network that the fluidsource is plugged into doesn't register that the dragon's head is a collision object. The tutorial doesn't do anything specific to make the two interact and their example works fine but mine doesn't collide at all. Has anyone done this tutorial series before and had success with this previously? Or are there any Houdini wizards out there who could take a look at my .hip file and suggest where I'm going astray? I've included some screen shots from the tutorial (Snake) and then from my file (Dragon), to give you an idea of what I'm working with. There's also the tutorial's .hip file, my current .hip file, and a link to the dragon geo alembic file included below. Any help or suggestions is greatly appreciated! https://drive.google.com/open?id=0B4nUEqhUvCtpeVFBS0xTYVhRY0U (Dragon Alembic) Thanks again ODFORCE, Chris (AUS) Mother_Dragon001.hipnc Snake_Tutorial.hipnc
  11. Hello to all... I have a scene where I have animated geometry written out and I bring it back in via a file sop. The animation is just of some rocks flying up in the air flying down inside some water. I'm using a vdb from polygons on the file and I'm bringing that into the dop network as a static object with the mode set to Volume Sample and pointing to the object in the proxy volume field . The problem I run into is when the rocks collide with the fluid, the fluid collapses. I can remove the proxy volume and reset the mode to ray intersect and things will be fine....I have tried to explore on how to fix this but I can't seem to find the solution... does anyone have any ideas? I can upload the scene later if needed. flip_tests.hipnc
  12. hi, I tried to use sourceVolume node as dynamics collision. So far, I tried the both of FLIP sim and pyro sim and can see a little bit influence, but it's almost not colliding at all. For instance with FLIP sim, I set: 1 - source volume > initialize > collision. 2 - check binding is correct. 3 - FLIP object > Guides > visualization > collision. I can confirm collision exists in viewpoint. The result looks almost zero collision. I knew this method is not accurate compared to staticObject method, but I could ignore a little lower precision. In fact, it's absolutely NOT acceptable result. On the other hands, when using staticObject, it always works perfect. Is this the exact reason that people combine to use staticObject node for collsionSurface and sourceVolume to add collsionVelocity? In conclusion, Have anyone succeed to use volumeSource as dynamicCollsion? What's differences of colliding mechanism between staticObject and sourceVolume?
  13. Please, I just need a couple of pointers I've been trying to set-up a pyro simulation, have some smoke rise up and collide with an rbdobject. I've uploaded my hip file and written all my questions and problem explanations in there. Plus I think that it's much easier to understand if you have my hip file instead of me trying to explain it here in text form. Please take a look at it. The gist of it is : The smoke has a temperature field. And I've wanted to lower the temperature field of the smoke that comes in contact with the geometry so I've come up with the idea to give the geometry it's own temperature field and tick the temperature merge option on the pyro solver. In order to create the geometries temperature field I plan to make a volume mask to mask out the smoke's temperature field so that i'm only working with the voxels that make up the geometry and then lower their values, the result will then be the geometries temperature field. I've listed all the problems and explanations inside the hip file please take a look Any suggestion is greatly appreciated Thank you Houdini_DOPs_pls_help.rar
  14. pop gravity node

    Hi, I made a deformed wave and I turned a patch of it into flip object. I wanted the patch of flip to move with the deformed wave mesh, so I bypassed the gravity node. I then have a geometry colliding the patch of flip particles but the problem I have now is that, because I already made it zero gravity on the patch, the sprays formed from the collision is now floating in air. I wanted the spray and foam to be influenced by gravity so they fall back to the ground but at the same time I want my patch of flip to move along the deformed wave mesh. Does anyone have any suggestions on how to achieve this? Thanks
  15. Hi there,I'm trying to change the colour of a primitive once a particle collides with it….but i don't want to use an attribute transfer because that gives me a gradient of colour on the primitive and i want to change the colour back after it's been hit and have it be a solid colour. So hit == green (0,1,0)not hit == red(1,0,0)Another problem i'm having is when i don't use an attribute transfer and write it in a python sop(code below) i change all the primitives colours in one go rather than individually where the the particle collides with each primitive.Not sure how to go about this, but here is the file attached.Any help would be much appreciated.CODE FOR HIT COUNTER AND PRIMITIVE CHANGE COLOUR node = hou.pwd() geo = node.geometry() from hou.session import * inputs = node.inputs() # bring in city searcher data pointcolliders = inputs.geometry().points() ship = geo.prims() if hou.frame() == 1: hitCount = 0 for p in pointcolliders: store = p.attribValue(“hittotal”) # get hittotal attribute from the pop solver hitCount += store # hitcount += store (to add number of hits to hou.session) hits = store green = (0.0,1.0,0.0) red = (1.0,0.0,0.0) #change colour of second input so object for s in ship: if hits == 1: s.setAttribValue('Cd', green) else: s.setAttribValue('Cd', red) particles hit each prim.hipnc
  16. Pyro + RBD Packed, How collision works?

    Hey guys, pls help me understand what's going on here: Check it out, on the RBD Packed node I can only use Bullet collisions (there's no other option in there) and it looks like the Pyro solver is using something else, like a volume collision. In this gif the RBD uses Sphere as collision representation and it's working perfectly fine, colliding with the original box shape: the proof: and the options avaliable: bullet.pyro.v1a.hiplc
  17. Houdini Pyro - Collision resize

    The gasresizefluiddynamic node resizes pretty much all the fields in the simulation, however if you have a collision volume that is moving through the sim you surely don't need that to be the same size as the density field, it just needs to be large enough to contain the collision object. Is there a way to set this up? I tried cracking open the node and removing collision and collisionvel from fields parameter in gasresizefield_smoke, I then created a separate gasresizefluiddynamic for just the collision fields. But for some reason my collision fields are still resizing to be the same size as the density field..
  18. Hi All! I'm wondering if anyone has run into this and found a good solution, it's been popping up in my low-to-mid viscosity sims for a while. Perhaps I'm missing something stupidly obvious? Collision geo/field are fine and the interface between fluid and collision object looks great before turning on viscosity, then I get these grid artifacts that are tough to get rid of. Reducing Surface Extrapolation way down in Volume Collisions helps but doesn't completely remove the artifacts. Also, using a high slip-on-collision value helps, but I usually don't want the sliding behavior with sticky viscous fluids. Reducing Grid Scale reduces the relative grid size and helps too, but the artifacts are still there, just smaller. Attached file is somewhat of a worst-cast example, just curious if other folks have dealt with this before. I know I can run some post-sim tweaks to clean up the collision surface intersection, but I've also noticed that the artifacts reveal themselves on the outer surface of the fluid if it gets thin enough, which is not so easy to fix... 01 - viscosity disabled 02 - viscosity enabled 03 - viscosity enabled, surface extrapolation 0.01 Thanks in advance for any help/ideas!! --Dave DStewart_FLIP_ViscousCollisionStepping.hip
  19. Hello everyone! I am very new to Houdini an need some help. I am trying to rebuild ""FLUID SOURCE" node with container settings "collision" to use it later in DOP with "Smoke Solver" and importing collision with "Source Volume". Just now have made with VDB surface field called it "collision" and create one more VDB from attribute "v" called it "collisionvel". I see difference between FLUID SOURCE and VDB collision is in first one create 3 scalar velocity fields and the second create one vector velocity field. Setup with VDB now have a problem my density ( made with "Source Volume") : theres no adding to density from SOP , but it works like copy. I will appreciate for any help! Thanks! P.S. Also i am interesting to rebuild it all without smoke solver, so feel free to comment all around this problem!
  20. 2D dynamics

    What's the best way to simulate dynamics with just 2D shapes? Is it possible to use any of the existing solvers to simulate rigid bodies, but also flexible curve/polygonal shapes that respect line to line collisions ? I've tried using the wire and the grain solver (with rest length on a network of lines that connect the points), but the collisions only happen on the point level, resulting in penetrations between shapes. Is there anything else I should look into, or a working example I can take a look? thanks a lot georgios
  21. Cloth collision like gum

    Good morning people: I'm a beginner in the 3D world. My main skill is photography and I'm searching a way to integrate some kind of VFX onto my images. Now I'm trying to generate a kind of big sheet of bubble gum colliding with a head. I don't know it the Cloth collider approach is the best or FLIP could be better. I'm stuck in this part, with this setup, I need a more stretchy look but I don't know how to achieve it. Thanks for your time. Best regards, Pelayo. clothCover.hipnc
  22. Flip fluid stick on collision

    i'm trying to make a honey simulation on a pancakes i have set everything except i dont know how to make the honey stick on the static object, i want it to keep falling but a thin layer of the honey stick on the pancakes anyone can help me to do this ? i'm using Houdini 16
  23. i have a problem with the splash that comes from collision object into the flip fluid ,i created a flat tank and i imported a strawberry obj and make it to Hero RBD with volume collision , bu tas you see the splash is too weak and the feedback of the fluid jumping after the collision is too high, and i got tired trying to solve it to look realistic particle separation : 0.045 = almost 10 mil density of the fluid : 1100 collision feedback scale : 0 collision force scale : 1 viscosity of fluid: 35 surface extrapolation: 0.001 velocity transfer: swirly kernal surface tension: 10 vorticity : on preservation rate: 0.1 use friction and bounce in solver is off Dop SUbsteps : 2 falling strawberries density : 100 solver type = RBD Houdini version : 16.0.621 hip file included + obj strawberry will be thankful if anyone helped me reference splashes: in this video the reference for the jumping fluid after the collision in the youtube video ate the 0:17 just a simple splash close to crown splash Chocolate_sim.rar
  24. I'm scratching my head over this issue. My FEM object is slipping through the animated Static Object slowly as it spins. The Static Object is set to "Use Deforming Geometry" and does not act as expected. FEM_slipping_through_StaticObject_slowly.hipnc
  25. Hi everyone, I'm currently working on a blast/pyro effect, and I need some advices about fast colliders. I've fast moving collider that doesn't affect correctly my pyro. the solver seems to be unable to correctly evaluate the motion of my object. Any idea about how to solve this problem. I've a simple animated VDB collider (2 fileds vel and collisionvel) Cheers Bertrand
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