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  1. Hey guys, I hope you are well, could you help me with something? I'm trying to create a fracture of an object with vellum grains, I'm using clusters to create the pieces that I want to break and a mask with mops to trigger the simulation, but I would like to increase the amount of cluster over the simulation time, is it possible with cluster attribute? for example, I would like it to break into large parts first, a few frames ahead, break smaller parts, and then smaller ones, and so on until it turns to dust Thanks a lot if anyone can give me some tips. I added a hipfile here thank you! clusters_v1.hiplc
  2. Hey everyone ! I would need your help on a sand simulation that I'm working on. It's a 10m high building which is supposed to crumble as a sand castle. My first thought was to try to do it with vellum grains, but the issue is that I'm getting limited by the amount of particles that I can have. Indeed, my GPU gets full and I've got the classic Kernel issue error in the console, meaning I just can't simulate my thing. I've tried to disable every OpenCL buttons that I could find on the solver (OpenCL Graph Coloring & OpenCL Neighbor Search) thinking it would just disable the use of the GPU for the sim, eventhough I knew it would make it really slow (at least it would have been computed). But it didn't work. Then I tried to use POP Grains cause from what I've understood, it's not using any GPU accelerated system. But I've got the same issue, the sim just can't be cooked. Would you have any suggestion for me ? I'm running this on a Threadripper 3960x and a RTX 3080. test_10.mp4
  3. I'm using a vellum grains setup to serve as a softbody sim for a fractured object (glued islands with separate, breakable glue for the seams, will point-deform source geo in a for-loop). Because the source geo is fractured, tet softbodies won't work, so I'm going the grains route. By and large it's working nicely, except that there are a few rogue grains that will fly off during the sim and I'm afraid that will screw up my point deform. It's not huge spacewise, so manually picking and blasting them after the sim but before the point deform wouldn't be difficult (and at this point probably more efficient, actually) but I'd rather do this procedurally since this setup is made to be reusable. Is there a way I can identify and blast out the misbehaving grains procedurally (presumably with the sim time-shifted to the last frame)? I presume doing a nearpoints-type-thing would eat into the edges or smaller islands, but I could be wrong. (And since they're more often in little clusters of two or three, just finding completely isolated points won't work.) Thanks for any help!
  4. Hi all,I am making a ground breaking effect in which a stone comes out of the ground and making primary debris and all.The condition is I also required to bring soil and ground dirt during eruptions I have managed to use the vellum grains to solve this, along I have used the "attach to geometry" constraints to make the vellum grains stick to the broken pieces. But now I also want during the collapse and hit on ground once the pieces fall on ground and make an impact ,some amount of dirt should also left on floor due to the impact. I can do this while playing with the breaking threshold but its not on per Debri I want to customize it so only some pieces would leave dirt rest not all. If anybody wants a file I can share too.
  5. Hi everyone, ive been using Houdini now for a few years and i absolutely love the power and the workflow with it but i am currently facing a problem which i cannot solve. the Orientation of my Grains are flipping and if I scatter stones on it, they are fliipping too. to visualize the Problem i copied grids on the grains. (check video below) I mean i could give it a straight up vector so nothing is flipping anymore but i want them accuratly rotate on the ground. In the Video you see grains on the ground and they should roll over the floor with proper rotations like marbles roll over a floor. pls help, i can not get my head round this... Thanks in advance! Max 2021-12-12 16-00-27.mp4
  6. Hi all,I am making a ground breaking effect in which a stone comes out of the ground and making primary debris and all.The condition is I also required to bring soil and ground dirt during eruptions I have managed to use the vellum grains to solve this, along I have used the "attach to geometry" constraints to make the vellum grains stick to the broken pieces. But now I also want during the collapse and hit on ground once the pieces fall on ground and make an impact ,some amount of dirt should also left on floor due to the impact. I can do this while playing with the breaking threshold but its not on per Debri I want to customize it so only some pieces would leave dirt rest not all. If anybody wants a file I can share too.
  7. Hi everyone, I am doing Houdini now for over 2 years and I love the software and the community! I recently face a big problem which i cannot solve on my own and cant find anything out there. to understand my problem you need to understand my workflow: since i got a redshift liceense locked with c4d i cannot render inside of houdini :/ so i usually create the simulation inside of Houdini and export it to c4d via alembic to render it there with redshift. (which is allready enough pain) whenever i create a particle simulation which has no constant point count like there are spawning new ones or they are dying somehwere i get really weird results in c4d with the cloner or rs matrix. i copy single polygons to the points in houdini and export it via alembic. In c4d I scatter now custom objects like different stones (stone A, stone B, stone C....) on the polygons and set distribution to polygon center so every single stone gets the same position as its particle. Or in other words: every polygon receives one particular stone. I also activate scaling from source so for example if i use grains with different size the scattered stones in c4d also get the same size and pretty accurate collitions. if now a new particle gets spawned or dies Stone A becomes stones B on the same location. this results in flickering evertime a particles spawns or dies. I also cannot use a random effector to drive the rotation or color of each stone because it changes every frame. I managed to find a workaround: I just keep the particle count the same without spawning or dying particles but i scale them to 0 or 1 but this is no real solution for me. Since i need to create a lager simulation and just pick out a small piece which i then need. So here is my questions: 1. Is this a Houdini Problem or is it a c4d Problem? 2. how can i fix it? 3. if it cant be fixed are there better workarounds? If you need a video or scene file or something from this problem let me know ill upload one but its for a client job and i cannot show too much. hope you understand and thanks in advance!
  8. Hi Magicians! I'm having trouble setting up my grain sim for a personal project I'm doing to get a better understanding of the mechanics in Houdini. In short I have a growing coral object which have to interact with my grains whilst it is growing. In my understanding what is going wrong. My vdb collision source is to jittery when it grows in my grains the vdb creates not smooth enough. I've tried adding a retime to my object to let it go more easy in my simulation but the problem keeps happening. If I go trough it frame by frame the vdb creates a surface and the next frame it is suddenly larger and that causes the grains to explode? Can someone please look into my .hip file to see if someone can fix my issue? I realy want to know the solution to this. I hope someone is willing to help me So much thanks in advance for the one that can help me with this. growing_object_grains.hip
  9. Hello friends, I have a issue with vellum grains. The simulation itself works well, but not with geo. The substeps are on 15. I copied the geo with copy to points. When I use spheres as geo, I dont have any problems, but with other geo the grains are still restless. You see it in the attached video. Can anybody help me please? Untitled.mp4
  10. I would like to delete vellum grains and their constraints so that I can pump more grains into the scene. This is something I've been struggling with for quite a while and all the tutorials I found do not seem to deal with constraints when deleting grains. I've simplified my setup to its bare minimum in the attached file. Any advice or relevant link would be much appreciated. Grain_Constraint_Delete.hip
  11. Hi all , I have a sandbox filled with vellum grains. I have the grains settle and then after a few frames part of the grains start to expand slightly. Has anyone experienced this issue of know what could be causing this? Thanks so much!
  12. Hey everyone! This is my first post here! I have a scene where I'm caching a vellum grains simulation to a disk cache. I'm having trouble understanding why it takes so long. When I cache the simulation to ram in the viewport each frame takes about 15 seconds, however when I drop a File Cache SOP and save it to my hard drive each frame seems to take about 3 minutes. Could someone explain why this may be? I have tried saving to another drive and it didn't help.
  13. Hi guys, To complete a personal project, I'm looking for a tutorial about the interaction between FLIP and Grains. Thanks for helping.
  14. Hello everyone, I am making a grains simulation that has a very long object (red box) for particles. Is it possible to make grains appear during the sim time (while my ship is getting closer to the grains), instead of showing all particles at the same time? That way I could save some sim time and instead of 5mil points, simulate around 1mil that is needed at that moment. I'll attach a low res sim video of what I have for now, so that it would be easier to understand what I mean. LowRes_Sim.mp4
  15. hi all ! I have a basic vellum grains setup. I need to modify the clumping to make the grains stick together less and for the grains to move more freely. Any suggestions which setting in the grain solver I should be modifying?? Thank you!
  16. Hey All! Question! Does the popAwake node work with Vellum Grains? I am placing it after the vellum source but it doesn't seem to have any affect? I'm not sure if i've made a mistake or if the popAwake node simply doesn't work with vellum? Thanks!
  17. okay so i've got a little issue here... I have FINALLY (After 30 hours of twiddling) got a really nice fairly stable sand grains anim going that interacts nicely with my char. so i've got my node network which is a basic off the shelf grains upres... i'm trying to wrap my head around whats happening in setseed_adjust_scale attribute wrangle node but i cant suss it out anyway what i want to do is vary the scale of my upres particles making some bigger and some smaller. so in my head i drop in a new attribute wrangle node (circled red in the pic) and i add the following: float @pscale = 1; @pscale = rand (0.002, 0.006); and BLAM! my pc fan after 30 seconds nearly ran out the window screaming!!!!! Its done this twice now and just locks up hou and the pc! so i'm properly stuck here - i cant figure out how to vary the scale of those upres particles - they are all the same size Anyone got any ideas on how to adjust this? ta ant
  18. Finished my first tutorial, hopefully you find it helpful learning Houdini!
  19. hi folks, I am trying to master my first Houdini project: an excavator digs a hole into the ground. What is causing the grains to jump out again, once the shovel lifts up? Could it be mass related or is it something that forces the grains to rest in their former position? D'you have any ideas? *D Please take a look at this small video: 01_construction_site_v4.mp4
  20. Hello, My issue I am facing is getting geometry(mushrooms) to interact with grains (soil). I've tried setting the geometry to a RBD hero object and the grains as collision geometry however this is not working. Any solutions would be greatly appreciated thanks:) Mushrooms.hipnc
  21. Dear friends I´m a new Houdini user and I´m trying to do something different from most of the sand sims. I have a thread of sand falling from the hole of an hourglass, and I´m trying to do build a sand object as the sand falls on the container bellow the hole. The question is, how can I direct my sand particles to become the object that I want? Any suggestions would be appreciated. Thanks in advance
  22. Hey, I'm currently trying to get my skeleton object to interact with my vellum grains sim, I want it to start from sleeping and get awakened by the character animation pushing through it to imitate snow. Any help would be appreciated! If you could explain more, how/why this makes sense to Houdini will be even better to build my understanding for the program as I'm still a noob Snow_Crawl_2.hip
  23. Hello Okay; Im starting with a sop with animated noise and transform, extract the velocity, which feeds my Pyro dop. After im using point deform on the result to output an animated poly sop model from the pyro sim. I was curious to add interaction FX using Grain with the resulting source. To have my pop source not static in my DOP, the only way I found was to have an impulse activation like $$F and a life expectancy very low (like 0.02, itùs in sec...). I have a few collision obj and forces. If i use a static activation like $$F=0, the sim reacts nicely and my object splash and roll, spread off on the floor and collide with objects like i expect. With small life, the particles dont reacts to the gravity, force and so. Which it's logic Afterall they are dying and being regenerated every time from the source position.// Maybe Grain is done designed for animated objects, or did i miss something? Thanks for your input, stay safe vincent* ________________________________________________________________ Vincent Thomas (VFX and Art since 1998) Senior Env artist & Lighting & MattePainter & Creative Concepts http://fr.linkedin.com/in/vincentthomas https://www.imdb.com/name/nm085962
  24. How do you turn a vellum grain sim into a polygon mesh? I feel like there has got to be a simple way of doing this, but all my googling has turned up solutions requiring building polygonal geometry in VEX. That seems like overkill for just a simple use case. Thanks for your help!
  25. i m still new to Houdini its been a month now, and I have hit a wall I m Currently trying to animate a character walking on sand and I want to use the Characters Geometry to activate the Grains. Problems: 1. I tried Importing an FBX Character and using its geometry as a source to activate the Grains....not working 2. I tried Importing an Alembic Character and using its geometry as a source to activate the Grains....still not working On either Case the grains continue to fall they do not SLEEP....... Please advice on best practices or please refer to tutorials
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