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Found 126 results

  1. 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
  2. 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!
  3. 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
  4. 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!
  5. 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
  6. 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
  7. 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
  8. 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
  9. 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
  10. 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
  11. 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?
  12. 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
  13. 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
  14. 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?
  15. Proper scale for FLIP

    So this has been mentioned in a few other threads but need some guidelines. My understanding is that FLIP has issues (unstable, flickering, collision, etc) for "small" scale simulations. By that I assume means anything under roughly a metre in largest dimension. What are some suggested starting points for scaling up your simulation for FLIP if its say, roughly a foot or so in diameter. 3X? 10 X? And what about speed to compensate. If you increase the scale 3X do you also need to speed it up 3x as well? There is also Spatial Scale on Solver and was wondering as a first step if i should try reducing to say .1 before I do anything else?
  16. With fast moving collision geometry and FLIP, what are some things to try to stop fluid from passing thru your geometry? Things I've tried - increasing substeps (using 8 currently) - reducing particle separation (I'm at .01 currently) What else should I try?
  17. Hi. What is the best collision method of POP simulation for debris in large scale destruction simulations? I think that such scenes in RBD are optimized by convex collision and packed geometry, so its computational cost is few. However, with POPSolver, we need to use Volume or Surface Collision (I thought ConvexCollision would work a while ago ...), so the computational cost will be quite high depending on the size of the scene. Is there an optimal workflow for generating a Pop simulation with PackedRBD simulation and accurate collision? Or is this something that you have to pay a reasonable cost for collision like VolumeSimulation?
  18. I (beginner in FLIP Fluid) have a FLIP simulation that gets crazy when I add a collision (static object) I use the test geometry shaderball, used 2 spheres with mountain sop, boolean with front and back of the shaderball. The two deformed spheres are the source. The rest (boolean difference) of the shaderball is the collision. Flipbook Without collision https://streamable.com/qkh2p Flipbook With collision https://streamable.com/922a6 Ii feel it has something to do with possible intersection between particles and collision geo, so I reduced the size of the sphere to leave a gap with the collision geo but the flip sim is still going crazy. Any idea? Issue with FLIP simulation.hiplc
  19. Hi! I'm making a chocolate dipped strawberry (strawberry model from 4dm-works.com). There are 2 problems. 1) When the strawberry falls into the chocolate, the FLIP is using both bounding box of the VDB and the VDB for its collision, creating this box around. VDB resolution is at 0.007 and uniform division for collision is at 500. (which I thought are high enough?) so I'm not sure what's up. 2) The 2nd problem is that the chocolate doesn't stick to the strawberry. I have the friction, viscosity, density and stick on collision on, but nothing's been happening. I have a feeling it's something super minor somewhere.. but I can't seem to figure it out. How can I fix this? (Bound_Stick_Question.hipnc) Thank you in advance for taking a look at it! -Y
  20. Whitewater leaks through surface

    Hello everbody! Im struggling with the whitewater sim. There are some post about it but they didnt helped me. I tried everything they told but its not satisfaying. I created the sim from the Shelfttool and played with some settings. First, the whiterwater particles were floating outside the mesh or didnt even collide. I pushed them closer into the mesh with some settings. The fluidsolver works fine. Then i recognized that the particles are inside the mesh. They are skipping the first surface and they are floating inside and now i need help I have another testproject with same problem. I hope you guys can help. I am out of ideas Here is the scene Thank you glass_scene.hip Glass OBJ.obj
  21. 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
  22. Hi Guys... How are you? I know there is a lot of information there that try to explain why this issue happens. However, I´ve tried to set up a basic scene to replicate the most common problem out there The scene attached is not the final or nothing at all... It was at the point of testing when I'm writing this post HOUDINI COLLISION FLIP ISSUES The main idea is this: Making the inside of the character-filled with liquid (just a little more than half). The liquid MUST be the same at all time. I had to invert signs of the static object to make it "work" And here the magic dust came along. THE LIQUID DISAPPEAR I´ve tried the following attempts with no luck so far: Reduce the grid size to 1 so the voxels of the flips have the same size of particle separation, Reduce the Particle scale to 1 to avoid conflicts in collision Try to multiply the scale by 3 to make it bigger and up the timescale of the solver to match it. I also try to advect the collision field with a volume source with VDB but it was worst and I discard that option in the minute Thoughts: I think it has to be with the particle collision mixture between volumes and particles. For some reason (i think particle accumulation) the solver reaps particles that are very close together and in the next frames, it does the same thing over and over until you are left with no particles at all... I tried to adjust the reseeding and even not reseeding at all and no luck either... It will be SO COOL to finally leave this point crystal clear to avoid future users to melt their brains out Cheers to all Peace! Wolf.rar
  23. Hi, I'm doing a vellum hair simulation on a character that starts partially under a ground geo. I also do other vellum sims (as foliage) that need collision with the ground. But my hair gets stuck under de ground geo. How can I make sure that only the other sims are colliding with the ground and not the hair? Thanks!
  24. Hey guys, I'm having some issues with a FLIP collision, seems my VDB collider boundaries are affecting the sim, anyone knows what can be causing this? I'm using static object + static solver with a proxy volume as collider. Thanks!
  25. Hi Guys, Very new to houdini so spare the studpidty, Ive set up multiple rocks in sops using the copy to points node. I wish to then perform a rigid body simulation on these rocks so that they collide with both the ground plane and each other. However, the effect im achieving is the group of rocks falling and interacting with the ground plane as a single large grouped entity. This is despite me setting the bullet collision data as concave and not concave. Thanks in advance all! Procedural Rocks.hip
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