Welcome to od|forum

Register now to gain access to all of our features. Once registered and logged in, you will be able to contribute to this site by submitting your own content or replying to existing content. You'll be able to customize your profile, receive reputation points as a reward for submitting content, while also communicating with other members via your own private inbox, plus much more! This message will be removed once you have signed in.

Search the Community

Showing results for tags 'collision'.

More search options

  • Search By Tags

    Type tags separated by commas.
  • Search By Author

Content Type


  • General
    • Lounge/General chat
    • Education
    • Jobs
  • Houdini
    • General Houdini Questions
    • Effects
    • Modeling
    • Animation & Rigging
    • Lighting & Rendering
    • Compositing
    • Games
  • Coders Corner
    • HDK : Houdini Development Kit
    • Scripting
    • Shaders
  • Art and Challenges
    • Finished Work
    • Work in Progress
    • VFX Challenge
    • Effects Challenge Archive
  • Systems and Other Applications
    • Other 3d Packages
    • Operating Systems
    • Hardware
    • Pipeline
  • od|force
    • Feedback, Suggestions, Bugs

Found 60 results

  1. 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
  2. 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
  3. 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
  4. Hi there, I've got some strange problems with the collision volumes in flip. The static object itself shows a clean, closed volume; the flip object on the other hand shows me a mess. Nothing is closed, the collision volume seems to be made of stripes. How does this discrepancy between static object and flip object happen regarding collisions? Actually the flip particles are floating inside the object. Got a new ship model and obviously some diffuculties making it work I also tried to use for each loops to convert each single object the shi is made of into volumes in order to merge them together insteat of turning the whole thing into a volume at once.
  5. 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
  6. 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..
  7. 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!
  8. 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
  9. 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
  10. 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
  11. 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
  12. 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
  13. 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
  14. Hi people! I'm learning some things in Houdini to create HDA's for cinema 4d or export vdb's simulations to render in c4d. In this case, I want to make a smoke simulation but I have one basic issue that I'm sure it solves with a simple way. I have one torus emitter inside of a tube but the smoke doesn't respect the tube geometry, It moves through it. How can I fix it? Thanks!!
  15. Hi! I'm a student learning Houdini, and I love it! Now I'm stuck with a problem. I want to use only one flip object that emit every frame from an animated particles source. At the first frame there's a 'base layer' of water that get emitted. The problem is that when new particles are added, then don't interact with the 'base layer'. Any help on how can I make the new fluid interact with the old one would be appreciated! I've attach a demo file with the same setup I use. FlipObjectBug.hip
  16. Hi Guys, I need some expert advice and insights on this project I'm working on. I'm doing some RnD first before moving to bigger scale so I can provide you guys with the HIP file. The objects however (barrels and table pieces) I cannot share with you. But maybe there's something in the dop nodes or solvers that you can spot right away. I'm working on a flood scene where there's a lot of debris and rubble that needs to be transported by the water. Please have a look at the video. The barrels seems to acquire a spin which at one point is out of control! I can imagine this could be the rotational stiffness... but the exploding (and stuck) piece of table is still a mystery at the moment. As you can see I'm also having trouble controlling the buoyancy of the objects in the fluid. Right now I use the density to try and float pieces but it's not entirely working the way I want it. To sum it up: - The wooden planks need to float - barrels need less spin and need to be embedded more in the fluid. - the tables obviously need to stop launching like superman . any advice or tips are greatly appreciated . High-RBD_count-in-fluid-006.hip
  17. Hey, I do have a little problem with flip collisions. I'm simulating a layer of caramel on top of which I want to add a layer of chocolate. The mesh of the first layer I converted to a deforming object. Collision volume and everything looks just fine. Unfortunately flip is going crazy when it touches this surface.
  18. Hey guys, working on a destruction shot which will involve a dragon thats being animated currently landing and somewhat destroying the building i have - Did tests with dropping spheres etc to get the constraints as i wished, then brought in a very rough 'previs' level peice of animation of the dragon i did - and as you will see from what i provide it doesnt collide correctly - i have tried increasing substeps - my collision volume matches my mesh almost perfectly, so really unsure what the issue maybe? Any help would be great (alembic and hip file below) and the youtube video link is to the latest flipbook i have showing the issue (please excuse my terrible dragon previs animation) Destruction_v2_t1.hip dragon_previs.abc
  19. Hey everyone! It's been a while since the last time I posted here because I was a little off from doing FX, but now I'm back on learning and stomped on some difficulties trying to do some collisions, flip and RBD simulations. The problem is that everything goes fine until a certain frame and the next one everything is exploding. I'm not sure if I'm not feeding the proper collision to the simulation or if the external forces override the movement of the particles rather when collision with a geometry takes places. A brief description of what I want to do is to achieve somewhat this kind of effect: -Water being pulled updwards, colliding with an object and continue the fluid simulation motion from there I'm attaching the .hip, some screenshots and a reference for what I want to do. Thanks a lot for taking a look and if someone can point me in the right direction I will be very grateful. Cheers! kamigawa_v002.hip
  20. Hi All, I have a working FLIP sim of a water fall that is colliding with my terrain mesh. I have added whitewater to the simulation and when I visualize the GREEN spray particles I can clearly see that they ignore my collision object. Is there any way to make the GREEN spray collide with the same surface as the WHITE foam?
  21. Hello artists! I'm trying to create an airfield alike effect but for geometry. Kind of like this effect : vimeo link Im also using VDBs for collision How'd you guys tackle this? Cheers and good work!
  22. Hello guys, I didn't get any answers from the sidefx forums so I'm trying my luck here. I am simulating urine from a medical cup going into a toilet bowl. Obviously, the water in the bowl is going to be clear, while the urine would be yellow in color. So I will need two separate objects to bring back into Maya for rendering (this is necessary). My current setup is successfully colliding with each other (the urine and toilet water). I am not sure what the correct way to set it up was, but this is currently how it is set up: * Urine fluid particles are sourced from a flip tank sop that's pruned– to match the shape of the cup that's holding the urine. That is then imported into the autodopnetwork through the flipobject sop and put into the first input of the flip solver. * The water in the toilet bowl is sourced slightly differently. For this one I did the same process by making a flip tank, pruned it and then made that a vdb and used the fluid source sop. This one is put into the fourth input of the flip solver. The reason I did this set up was I just could not get them to collide with my previous method. I tried making them both into flipobjects and merged them with mutual collision (i also tried left affects right) but they wouldn't interact. With the current set up, they do. Now I am wondering, how do I isolate the two different fluids so I can export them as separate objects, is it possible? Would appreciate some help, thanks!
  23. hi everyone i have a small issue here with my sand grains (wet grains) - i'm trying to get my mesh to collide with them but they seem to be jumping about a fair bit as the character moves. I'm not sure what i can do to adjust this jumping about does anyone have any ideas? playblast below to show you what i mean. I cant share the scene file right now sorry but the jumping of particles is quite noticeable here ip.mp4
  24. Hi guys, I just want to ask one quick question. I am using bullet solver and want to count hit value of pieces with collision geomectory. I tried pop collision detect also but its not working on rbd. thanks
  25. I am building out a Big Bang collision. I have a very large sphere that I use as the all encompassing universe. This is a static object. It is the Universe Sphere. I then have an RBD that I set the "center" parameter/attribute to the Universe sphere center channel. This sphere serves as the Big Bang, which has been fractured via Vonorni. I use a smaller sphere, whose "center" parameter is also set to the Universe Sphere center channel, as the initiator of the collision. I set the radius up for the Spheres. The Initiator Sphere is key framed with a Uniform Scale of 0 and then the very next frame it is set to 1. The size of this instantaneous expansion sets the velocity. I set the mass of the Initiator Sphere way up and I use a Position node to keep this Sphere for the most part locked down. I set bounce to 0, rotational spin to 0, and friction to 0. Over all, these settings, for the most part, keep the Initiator Sphere locked at the center of the Universe Sphere. However, I am getting a very slight wobble, before the Initiator Sphere settled down into a perfect center in reference to the Universe Sphere. What I am asking is what is the most efficient way to stop the wobble and lock the Initiator Sphere to the center of the Universe Sphere. I have looked at Constraints, however, the universe sphere is a static object, not an RBD, so I am thinking constraints will not work. I am looking for a very uniform collision across all out ward moving vectors, much like a uniform nuclear detonation. Any help would be much appreciated.