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Found 137 results

  1. Hi everyone, I have a persistent problem with flip simulations. I have a guided ocean layer sim with a flip surface and a boat sailing (static object in the simulation DOP). The problem being that the inside of the collision boat is filled with particles every frame because of reseeding. I already have "Kill inside collision" checked in the Ocean source node and I don't want to turn off reseeding. Is there anything that can I do to avoid the reseeding inside the collision vdb? Am I missing something in the workflow?
  2. Hi! First post here. After months of lurking and picking up tips from other users topics I need more direct help. I'm quite new to Houdini and I hope you share some ideas. With given FBX meshes, I have to simulate a gate being rammed out from a wall. Chunks of portal around the gate are supposed to be pulled out with it, hit the ground and crumble into bricks while the rest collapses. Gate itself is animated with bones, not physics-driven. After many experiments, I couldn't achieve that two-step fracture (big pieces falling on impact and then crumbling). This is what I've already tried: 1. I've split all wall FBX into bricks using Voronoi fracture fed with array of points (four pieces total: the portal, left, right and top parts of the wall). 2. I've divided the portal into chunks by grouping fractured elements with separate glue constraints. 3. I've created set of constraints for each piece.). 4. I've constrained all parts of the portal to the animated gate. 5. I've imported gate and wall as RDB Packed Objects to a DOP and fed it to bullet solver. 6. I've set up constraints networks for each piece with SOP solvers connected. The idea was that the portal is connected to the gate by glue constraint with infinite strength (-1) and pulled that way out of the wall. After few frames the constraint is severed by deleting lines in SOP solver. Constraints for individual chunks remain until they are broken by impact with ground. Meanwhile the result is that: when portal-gate constraint is removed while the portal is still in the wall, it's being abruptly shot upward. It looks like the animation (which I can't alter) forces meshes to overlap, so they pop when it loses control over them. When the constraint is removed few frames later when the portal doesn't collide with anything, it gains such high acceleration already, that bricks spray all around as if it has been an explosion. I suspect that my pipeline my be noobish, but I couldn't find any resources on similar cases. Unfortunately I can't share screenshots nor files as they are part of a commission. I'll appreciate your help.
  3. Hello everyone, I'm trying to do a multiple explosion effect on a piece of geometry with a glass material and I have some issues with concave shapes. Since the object needs to be transparent I cannot use any kind of pre-fracturing, otherwise it would show. (picture 1 & 2) So I setup a DOP network with a SOP solver inside to fracture the geometry dynamically. (picture 3) It works fine and the explosions are happening as planned. But since the geometry is concave, a convex collision shape is automatically created around it. (picture 5) And this causes the pieces created from explosions to be pushed outside instantaneously (picture 6). So I've searched for ways to handle concave geometry and this is what I found: Use the "concave" option in the "rbd packed object" node. It works! (picture 7). But it is excruciatingly slow, and this chess piece is part of a larger simulation with other chess pieces with similar issues. So in the end it would be difficult to work with everything being so slow. Decompose the base geometry into convex shapes. With the "convex decomposition" SOP for example. Since it produces several pieces, I can't display the result directly as the object is transparent (same issue as picture 2). And since I fracture the geometry dynamically I don't see how I could replace the simulated geo with some display geo in the end. Maybe I'm missing something here, but I don't know how to replace proxy geometry with display geometry when the proxy geometry is dynamically fractured. The "compound" option in the "rbd packed object" node The description of this option looks promising in the documentation, but it specifies that you need to use a node to generate some data, and that node is deprecated... It is replaced by another option called "Create Convex Hull Per Set Of Connected Primitives". But as far as I understand, your input geometry needs to be made of several "pieces" for this option to be useful. Is there anything I missed here? A method for generating collision shapes that doesn't involve breaking your geometry into several components?
  4. POP particle collision/final resting

    OK... I think I've exhausted my button pushes and research. If anyone can give any pointers about getting my collisions/debris to actually appear to rest on the surface and/or interact with the moving model I would be very thankful. Currently, the `debris` appears to come to a final rest above the surface. I've included the scene and ref'd geo. quinniusMaximus_recog.zip
  5. Hi everyone, I have a simple sample scene here, having problem with the flip collisions. - I have a basic deforming sphere geometry that has a colliding liquid which works fine. -Problem part it i also have some liquid pouring on top of that deforming geometry (needs to collide the outer side of the sphere) but seem like there is a square bounding box around the collision (due to negative sdf) geo which gives me unproper collision outside. How can i have correct collisions for both inside and outside of the deforming mesh? thanks. Flip_InvertedCollision_Problem.hiplc
  6. RBD and its sleeping properties

    I set up a scene with crates that I want to get destroyed by a flip sim. figured out that I had to put a attribwrangle with i@bullet_sleeping = 1; so that RBD stays in place until the FLIP collides. The problem is now that with a little hit of flip to a group of crate the push activates all of them to break. I am a noob, but found that there is a threshold to control the amount of impact to activate the RBD. I just dont know which one of these it is and how to apply it to wrangler. bullet_angular_sleep_threshold bullet_ignore bullet_linear_sleep_threshold Documentation found here : https://www.sidefx.com/docs/houdini17.5/nodes/dop/rbdpackedobject.html Here is the original failed vid: https://www.dropbox.com/s/dl8ze5rv4vf6gse/Test.mp4?dl=0 Here is current failed test vid: https://www.dropbox.com/s/sa4sumxfqpqmdhq/Flud Test2.mp4?dl=0
  7. I'm looking for some guidance with an effect. I have a pyro simulation of some smoke hitting a floor and the collision is working fine. I want to take the collision information from the sim and pass it back to the floor geometry as a point attribute e.g. an attribute that is 0 when the sim starts but as soon as the smoke touches the floor the attribute changes to one. If anyone that could point me in the direction of how best to achieve this, I've tried to play around with the 'Gas Impact To Attribute' node and I could not work out how to properly wire it up. Thanks! SmokeCollision-01.hipnc
  8. Vellum Collision Problems

    Hello! I am trying to deepen my understansing of vellum by building the solver netowork myself. I have hit is very enfuriating sustuation were my character litterally walks out of her pants. When I use the sop based solver this dosn't happen. I am sure I am missing something but it seems most things I have tried are giving me the same result. I am using an almebic cache for the collider, and cloth geometry brought in from Marvelios Designer. I am using an collision source node to generate a vdb for collisions, and using a staticObject set to “Use Volume Collision” and “Volume Sample” for division Method. Here is what I am getting
  9. Hi, I would like to create an animation of blooming flower. I've created the basic setup, but I have a problem with intersecting petals. Does anyone have an idea how to get rid of those intersections without deleting whole petals? Thanks in advance for all the answers. flowertest.hiplc
  10. Hello guys, So ive been trying to test the difference between using a collision object or a collision source in pyro sims. I still cant grasp the difference between each other and when should I use one or the other. What do you think? pyro.mp4
  11. Select collision particles

    Hi, I have a geo diving in flip Problem: I like the ripples at the beginning, but I want to slow down the ripples that get too high Question: how can i select only the particles that collided with the geo? I want to add the particles that collided with the geo to the group and limit their speed or maybe add a drag force to the selected group. Is this approach correct or is there any other way to keep the low ripples and slow down the fast ones? Thanks IMG_6198.MP4 Also online preview https://yadi.sk/i/yxXCQ8Yghz11Jg
  12. Hi everyone, did a pyro sim along with a collision object. When I up the density from 1 to 4 in the pyro shader, the voxels are getting visible (attached an image to the post showing the issue). Is there any way to prevent that or soften the voxels on the outside in a post process or something? Cheers, Christian
  13. Vellum Cloth Collision

    Hi everybody. I have a cloth rack with hangers and clothes on it. The rack moves along the path. I simulated and cached the hangers moving with the rack. Then I modeled and draped the clothes on a static hanger and copied the draped clothes to each hanger to simulate the clothes on the moving hangers. I thought instead of using static deformed object it is better to use RBD fractured object (making it inactive) with point position, translating the transform of the hangers, so it would not load the collision geometry every frame. To help the vellum follow the animation of the hangers I also soft pinned with match animation those parts of clothes that "touch" the hangers. The problem is, after a couple of frames, the clothes start to penetrate the hangers. Increasing the substeps (tested with 10 and 20 substeps), collision passes, polish, post collision passes doesn't solve the problem. So generally I have 2 questions, first is: which collision type is used in vellum simulations: Bullet or Volume? And second: any thoughts on how can i solve my problem? Loading hangers through static deformed objects also dramatically increases calculation time.. Or is it the only option for vellum? Thanks in advance!
  14. Hi everyone, I have a simple fracture simulation that I would like to use as collision geo in a vellum sim. However as vellum is particle based, and the collision geo is very low poly, I need to somehow increase the geo subdivisions for the fracture sim geo. I've looked at using the subdivide node, but this doesn't seem to work. I'm hoping this is a simple one and I'm just not aware of the right node to drop in! Thanks in advance! Glass.hiplc
  15. Static Object Collision Guide Problem

    Hi! just got a little issue here, i have a moving static object with a particle sim and i don't know why but the Collision guide show up on my render and i don't really know how to undo it unless i remove my static object completely and that's not what i really want. Thanks in advance!
  16. Hello; I tried to deform a cloth object with the smoke, but how can I stop the smoke from passing through? Thanks for helping. Cloth_Smoke_Collision_01.hip
  17. Hi I'm currently following the vellum docs for using the collisionignore and collisiongroup string attributes. Everyrthing works fine when I specify the collisionignore group directly, however when I try to tell vellum to ignore all groups except for one that I specify, it doesn't work. I've made a basic scene to demonstrate the problem. Here is the code that I use: s@collisionignore = "top"; - This one works s@collisionignore = "* ^bot"; - this one doesn't work TLDR “* ^foo” rule stated in vellum docs doesn't work fo me, what am I doing wrong? Houdini dosc for what I'm talking about here(collisiongroup and collisionignore): Docs intersections.hiplc
  18. Is it possible to have a mutual collision between Pop Solver, with POP Fluid, and an RBD Object ? Something like the Feedback Scale we have in Flip Solver. It's a basic Setup, I have a box, blasted the top edge, and an RBD Sphere in there, and I emmit Pop Fluid and I'm trying to achieve mutual collisions, so to make the sphere float on the liquid surface
  19. Hi Everybody! I have been following this amazing tutorial done by Vladislav Lavrenov. Everything works just fine but I'm trying to do some personal variants to this. I was trying to make the whole simulation collide with an object, in particular with a wall. I achieved in doing so but for some reason any geometry that gets put inside my popnet as a static obj gets taken by it as a new source of particle emission. Each point of the static obj is emitting particles or a piece of geometry of my voronoid fracture. I can't undestand how to via vex how to ignore the static obj geometry. Here in attachment are some screenshots of what happens... as you can see on the wall points there are particles that shouldn't be there. I guess everything is happening in my copy node and the voronoid geo gets copied in every point of the scene... but why, and how can I fix it? I'm really stuck and need somebody with more experience to help please. Here is also a copy of the project. Thanks in advance for the help!!!! Simone newexplosion_collision.hip
  20. Vellum pyro collision

    Hello! I'm a beginner and asking for help as I stumbled upon this problem..i cant seem to find a solution..i would like to make smoke signals...with a vellum cloth. I tried everything or so i think: so, I used sparse pyro for the fire simulation, then made a quick vellum cloth, pinned it in the air and animated it. For it to collide it, I used point velocity and used popadvect by volume for the cloth. It worked, until I animated the cloth (because to make smoke signals, the cloth must go up and down). Then i tried even by adding the deforming collision node into the dopnet..but it's even worse.. I would like the vellum cloth to affect the pyro and make smoke signals in that way! Please, can anybody help me? I'm adding the files. logs.obj fire_sim_3.hipnc
  21. Hello guys, I am doing a new test with vellum hair. I am trying to sim a sort of object going through some vines and I would like to have a opening like curtain effect but I cannot make the hair react like I would. Feels like they are stretching always no matter what is the value of stretch.. Am I considering something in the wrong way? Any suggestion help would be great thanks test_vines.mov tree_test_v002.hipnc
  22. Volume Source as Collision

    Hi, Recently I have trouble when using the Volume Source as a Collision for my pyro scene. I cache out the object in VDB, then loaded back into a new scene. Why my smoke still don't collide with the collision?
  23. Hi; In my FlipFluid simulation, I tried to use a volume as a collision, but it doesn't work. How can I fix this? Thanks for helping. VolumeCollision_Test_01.hip
  24. Hi guys; To fill a bag with some candies, I tried to use vellum cloth for the bag, an rigid body as candies, but I can't make them to collide with each other. How can I fix it? Thanks. Test_01.hip
  25. Hello, I have noticed something interesting which I don't understand, but maybe somebody out there does. I created a Wave Tank shelf tool then a sphere and I hit the Deforming Object shelf on the sphere. Now I'm checking the OUT_INITIAL_VELOCITY node with PointsFromVolume and volumeTrail nodes. When I wire the collision geo into the collision input of the OceanSource node the velocity is become wierd as you can see, and it affects on the simulation in a bad way. It's just shelf tool! I didn't make any changes. I use 17.0. Is it normal or is it a bug or what is it? Is there anybody, who knows it?