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Found 92 results

  1. Granis collision help

    Started trying to make a Hour Glass effect but when i press play the grains appear on the outside of the geo, not sure what the problem is any ideas? HourglassSim.hipnc
  2. Hello, The title may be not that clear so rather then tell, I will show what I need to achieve first and then I will describe my approach (or better say approacheS, because I have been banging my head against the wall for quite some time with this). So basically here is what I need (did this quick and dirty animation in C4D): https://www.dropbox.com/home?preview=test.mp4 Now the tricky part is that this animation has to loop. Initially I started in C4D. Made some particles crawling along the surface of the statue, cloned some primitives on those particles and applied dynamics. It all works great but how do I loop it. Simulations are are very tricky to loop (especially in C4D) so I decided to go the Houdini way and try to build procedural setup that would give me similar result. My initial thoughts of the setup are the following: - scatter points on statue - make them move with the noise and use (minpos() function to stick them to the surface), and use periodic noise so the movement can be easily looped. - every frame attribute transfer normals of the statue to the moving points, so that when I copy objects they will be aligned to the surface - copy objects onto points and make sure there transformation axis is at the bottom so that when copied they appear on the surface of the statue - check for intersections with the statue (still not sure how to approach it but as far as I remember there is a way to see if two meshes intersect or not - if they intersect, move the object away from the statue along the normal of the point it is copied onto (I think this will have to be done in solver so that I move it slightly and then check for intersections again, because the distance the object has to be moved may differ) - I still do not know how to avoid intersection between all the objects on the statue themselves ( do not have any ideas so far) For now I am stuck on trying to loop the movement of the points. I can loop them easily in 3D space but when I minpos() them on to the surface they jump from time to time. I understand why this happens but can't figure out how to avoid it. I tried attrib transfering the normals of the statue to the points every frame (in solver) and then calculating the cross product between normal of the point and vector generated bu the noise. This gives pretty smooth movement but the loop breaks of course as you may have guessed. Anyway, thanks for reading this far. If you have any ideas on how to make it work, please let me know, I appreciate any input. I have posted same question on the SideFx Forums on friday but it is still been reviewed (takes so long). Maybe I am overthinking things and there is easier way to do it say in C4D, in case you know it, please let me know. And do you think my thinking process is somewhat right? Looking forward to any help. Have a great day everyone!
  3. Houdini Pyro Collision

    Hi there everyone. This must be a common question but I just cannot seem to get the Pyro Collisions to work correctly there is defiantly something I am missing and I would greatly appreciate some assistance. So this is the issue I am having. Below you can see the Multi Field going through the Collision Field where there are no holes. This is the Multi Field. Here is the Collision Field on its own so you can see its a solid Piece. This is the Temperature Field. This is another angle of the actual Geo at the same frame as the images Above. So I just wanted to mention what I have observed and what I have tried. first my observations, the Multi filed is only partly interacting with the collision field, in that some of the smoke travels along the ceiling of the roof before finding an exit and pushing outwards. Secondly have I have tried, Is using the Houdini shelf Deforming collision object but it only dose 2 frames then hits my 32gb memory cap and my system crashes and restarts. This is if the mode in the Static Object is set to Volume Sample. If I try Ray Intersection it dose not work, there are holes in the collision Field. so the method I am Trying to get right (Based on the Images above) is the secondary Volume Source set to collision. Here are my VDBs and I am merging in the Cached RBD Data. And this is my Volume Source for that VDB Surface If you need anything Please Let me know ! Have a Great day, Jody.
  4. Hey folks! I was hoping to gain some understanding on how I might 'mask' out areas from the advection process. I have a recursive growth setup and want to add some objects into the scene where the growth will react to and grow around it... Im not sure the best way to go about this so im not subtracting the colision surface from the growth vdb every frame... ideally some vops setup to multiply the negative space of the collision geo with the direction of growth (velocity) so that it zeros out as it nears the surface. Im using a modified version of this setup i found on the forum. attached youll see the surface i want a collision with. http://fx-td.com/content/misc/recursive_growth_v2.hiplc Many thanks!
  5. I am trying to separate geo that intersect. I am trying to do this with simulation. I am able to do this via the wire solver (File example) but I need to be able to separate more custom geo then just "tubes". What I want, is to first separate the geometry (custom geo), then take that geometry and use it with the FEM solver. I am not able to make the FEM or Grain solver push geo away from each other, when it intersects like I can with the wire solver. Is there any trick or something that I have overseen? I am able to push away points from each other via vex, but it is pretty slow, because it has to iterate over a lot of points, and run more then ones because some geo that is pushed, will intersect with other geometry, and it is not that easy to setup if I don't start with lines, but real geometry, (like geo from zbrush) wire_separation.hipnc
  6. Hi, I'm looking for a way of inheriting color on collision while using bullet and packed primitives. Let's say I have an object colored white - and I would like every single object that it touched to be colored white as well. Prefereabli those new "infected" object would infect others on collision. I did some search, found some topics on POPs using "hit count" - but nothing regarding bullet. Could you just point me in the right direction? Some use of collision data? Regards
  7. Flip PopCollisionIgnore?

    I am messing around with some FLIP collision effects and have found the popcollisionignore node doesn't work with FLIP sims. I'm confused on why exactly it doesn't considering its operating on the geometry, is this a problem/setting with the FLIP solver itself? It obviously works very easily with a regular pop sim but no dice otherwise. My plan here is to shoot the particles into an object, once the particles are inside the object it switches to collide with the object, and the particles are stuck to swirl inside of it. This would all work fine with a sop solver and some group nodes if the popcollisionignore worked as intended, can someone maybe point me in the right direction? Thanks! flip_collision_ignore.hipnc
  8. I'm having some trouble making my clustered pyro sim have collisions. It's a custom setup where I make a couple of containers with instancing at start frame and I've made a small change in the Gas Resize Fluid Dynamic DOP to resize each container separately based on $OBJID. The problem is that when I add collision objects, my density just doesn't show up or source anymore. When I use the shelf tool to make a static or deforming collision object, I don't get any smoke. Or I get it in weird places where the containers overlap. And when I use a Source Volume node set to Collision, all I get is what appears to be the Source field, but there is no density coming from it. When I disable the Source Volume node, density is sourcing and moving normally again. I've tested it in small scenes with basic geometry where I use shelf tools to setup the clustering and collision and then it seems to work. With the Source Volume node gives me the same issue, except when there's just 1 container (so no clusters). Then it works just fine. Since the shelf tool works, my guess is that I have to set some setting somewhere so that it works with instancing. I've been comparing the working test scene with my scene, but I haven't found anything yet. I'm afraid I won't see what I need to change even if it's under my nose. I've added the .hip file, but beware as it makes quite a bit of geo. So expect some loading time when you go in the SURFACE node. Thanks for any help! Eckhart TerrainDemat.v013.hip
  9. Pop Collision Ignore + Grain Solver

    hey guys, is there a way to make the Pop Collision Ignore node work with the grain solver? I really need to avoid the collision of one granular solid object, it works fine with normal particles but not with the grain solver. grains_avoid.collision_1.01.hiplc
  10. Hi everyone, I am trying to set the values to a collision field in a gas wrangle. I am using the gas build collision mask node to create the necessary fields and then I am trying to set values with a gas wrangle. Is it even possible to do it this way? I have a example scene that shows how I set it up now, that doesn't work. My purpose for this that I want to be able to simulate a 2d smoke simulation and collide to an object on a different height for every voxel. I will eventually want a separate height field that will accumulate the density and this heightfield will be the Y position for the voxel to check the collision. I am quite new to smoke/pyro simulations, so this scene probably doesn't make any sense gas_collsion.hipnc
  11. Collision object in Pyro sim

    Hi everyone, I am working on a smoke simulation and i have imported my collision object with source volume into my Pyro sim. No matter how much I increase the smoke divisions as well as reducing the voxel size on colliding geometry I still get jagged edges when smoke interacts with it. I have attached a screen capture here to make it more clear. Is there any way to smooth the jagged edges or am I missing something in the process? Any tips would be greatly appreciated!
  12. I have a collision object that I want to push through a particle sim area. I want to remain the small sim area (box) so the particles stay inside the tight area but once it gets hit by the collision object the particles that were affected by the object fly off. How can I achieve this? Thank you, this is the file I am talking about. Particle Collision Tester v03.hip
  13. Particle collision Physics with RBD

    I'm trying to get good physical interaction between a baked RBD geo and a particle system and the particles seem like they are either all stuck or all slide with nothing in between? I'm bringing in the RBD as a static object collider, with deforming geometry turn on, and set the collisions to Use Surface Collisions (the green guide one). The particles collide but for the most part they stick really harshly even when friction is turned down all the way. If I go onto the pop solver and in the collision behaviour tab, set the response to slide.. they slide but then it looks like its on ice and the friction controls are disabled. Any ideas how to get a good setup? I'm trying to make something like rock debris on a cracking ground surface. so there should be some tumble and roll but eventually come to a stop, maybe a slight bit of bounce but not really too "bouncy" either.
  14. Hello, today I am facing very difficult problem, maybe you could help me in this struggle. Scenario looks like this: I received animated tree exported from SpeedTree as an alembic file. Now in Houdini it looks like wind is moving leaves which is perfect. The problem is I would like to collide with the leaves with RBD objects which are bouncing around my scene. I would like to keep my “wind” animation on a tree but make the tree responsive to any objects that may collide with it and make it so the leaves would bend on collision. Is it possible ? If so what would be the way to achieve such effect. Have a nice day and thank you for your input in advance. P.
  15. Flip Collision issue

    Hi does anybody familiar with that issue? it happens often and usually gone after some changing but now its still there and i cant fix it, as u see here it looks like a bounding box from colission ship, so i found its a velocity of collision from fluid solver, i use volume representation of the ship, and there isnt any colission on the ship but the fluid solver makes it itself and it wrong, how to do this correct ?
  16. Fluid not colliding with object

    Hi Everyone! I have an issue with a flip fluid sim not colliding with any objects. I have made the objects static objects, and the settings I have on this collision object are working perfectly fine in another scene with a different fluid sim - which might indicate in may be to do with the fluid? Are there any settings in the fluid that could prevent it from colliding? Let me know if you need more info. Thanks!
  17. How to view heightfield collision

    Hey, I am using a heightfield as a collision. However, when I try to view the collision by turning on show guide geometry, nothing shows. Is this normal? I want to point out that the collision works, I just cant see it. thanks
  18. Hey guys Well am very much new to houdini and working on some mini destruction scene, The problem is i have turned both window and lamp to rbd packed objects so that it collides with the car. But the lamps are falling way too before when the car actually hits them, Kindly let me know the solution. here is my file - car project.hip
  19. Hi, Has anyone else noticed that the cloth collision radius has no effect on actual collision distance? No effect on cloth to cloth or cloth to other collider types. I would appreciate a confirmation and of course a workaround if anyone has managed to find one. Thanks
  20. 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
  21. 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!!!
  22. 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
  23. 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
  24. 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
  25. 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!
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