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Found 52 results

  1. I've been stuck on this for a couple of days now and would love to hear you guys' input. I have close up shot were a character's feet is pushing through snow up to his ankles. I decided to try grains for this (it's my first time really using it) and to get the snow together I used the constraints set outside in the grain source. Mostly the sim is working as intended but I'm getting a lot of unwanted fast movement from some particles (as if they're trying to keep the constraint but not really keeping it, so they pop in and out, and that results on a flickering on the meshing. Did anyone come around this problem before? I am up for any solution at this point, even trying another method.
  2. Random pop bounce direction

    Hi, I'm trying to achieve a simple effect, but am struggling to get my head around it. I'm sure I'm overthinking it but if anyone could help me that would be great! I'm trying to get a random bounce direction on particles when the collide with the ground plane. As if the particles were small stones bouncing randomly due to a bumpy road surface. I've attached a hip file with the basic setup. I was thinking maybe you could inherit a random vector as the collision happens, but couldn't seem to figure a way to do it. I know various sources have mentioned the old "gain normal" parameter, but this no longer exists. Any help would be much appreciated. odforce_randompopdirection.hip
  3. Hi guys! Suppose I have a sphere filled with particles, and there is a growth map on it. I am activating the particles based on this growth map and a wind force blows the active particles away. I am only emitting on the first frame. copying the growth map attrbs via sop solver. If my wind force is too high it will cause gaps in between the particles as they are pulled away. Will dop/pop substeps work properly and fill the gaps when there is no emission happening? The growth map has in between frames, I've put a time blend sop to be sure. But I am having a tough time getting the substeps to work Would be great if anyone has any suggestions. Thanks!
  4. Hi all, I'm building a crude crowd-like system using POPs and I'd like to copy my imported walkcycle on to the particles with a random timeoffset. The old method of copystamp with a timeoffset value on a timeshift node works - but it's really slow. I've been reading up on the for-each / compile block method but I'm unable to compile timeshift or file nodes. So my question is - is it possible to do it with a for-each/compile setup or am I stuck with the old copystamp method?
  5. Hi guys, I’m trying to get POP object and a FEM object to have two-way interaction. The pops are colliding with the FEM, but the FEM object is not being affected by the impact of the POPs. What do people think is the best way to get this to work? Currently I’m playing around using a SOP solver on the finite FEM object to bring in “feedbacks” input. This seems to contain a the particles that hit with fininte element. The pt’s have hit attributes and, “impulse” and a normalised “normal” attribute which I assume is direction. Not sure the best way to apply these feedback points to the finite element. Which attr should I modify and what do we think is the best way to lookup the "feedback" data? Perhaps a point cloud lookup? And suggestions greatly appreciated!
  6. POP Grains Collision Issue

    Hey there, I'm having an issue with my POP grains sim. I'm trying to simulate spaghetti or noodles on a plate which are thrown up into the air as the plate is flipped. I was able to modify a scene file to create the noodles and create collision geometry based off an alembic file I was provided. However I'm having two issues: 1. My grains don't stick to the plate the entire time, some of them go through my collision geo 2. I'm getting some very weird stretching with the grains as the sim progresses. I'm not sure if there is some other collision elements that I am missing or settings on the grain nodes that I need to tweak. I've attached a flip and hip file. Any advice would be greatly appreciated. Thanks! noodles_v01.mp4 noodles_v04.zip
  7. Hey all, I'm banging my head against my desk trying to figure this out....I'm attempting at creating a spaghetti-like simulation where noodles start out on a plate, and then the plate is flipped and throws the spaghetti off the plate. I'm generating some noodle-esque lines using pops and grains but I cannot for the life of me figure out how to get them to not intersect. Am I missing something? I was also hoping to add meatballs to this at some point as well which would be sitting on top of the noodles and then get thrown off the plate as well....would this be accomplished with adding a multi solver to my pop network that combines the popsolver with a bulletsolver? I've heard grains and RBD objects don't play super well together so I'm not sure which is the best approach for something of that nature. Thanks for your time!spaghetti_RD.hipspaghetti_RD.hip
  8. More Particles Following a PATH!

    Hi Guys, I have a system of Pops where particles are following several splines with a PopCurve Force node. I got everything working the way I want except for one small detail that I have not been able to figure out. The detail is how do I align the particles so that they face the direction of the spline? I don't want them to bank along the spline per se but just have an axis aligned to the spline almost like dominos or people marching in a single line along the path of the spline. It has to feel very organic which is why I am using POPs with forces and things like that as opposed to doing it in SOPs. I thought maybe a POP LookAt would work but I am not sure how to get the curve alignment data to POPs. I am sure this has been done twelve ways from Sunday but I am pretty new to Houdini and haven't able to figure it out fully as of yet. Anything advice on this would be awesome. Thanks! Cheers, Christian
  9. I am trying to get some temperature data that I have calculated on the output of a particle simulation to make it work with the pyro shader, but I can't seem to get it to transfer. I am using Volume Rasterize Points to get the particles into being a volume, which is working really well, but I can't seem to get anything but the density field filled. The node supposedly takes point attributes and fills a volume field with the data if it exists as both a field and a point attribute, which these do, but I keep coming up with empty fields. Failing that, I tried to brute force them over using Volume from Attribute, which I had successfully used elsewhere in the scene, but to no avail. Still giving me empty fields. This has started to become quite vexing, as I think it should be working how I have it setup, and it isn't. particleTest1.hip
  10. I am trying to do a sort of Sci-Fi explosion, still deciding on the story behind it, but I know the look I am going for. I want to have an energy core going critical with energy masses spinning around it as if following magnetic field lines. I finally got my field lines working right and got them into a vel field, but now I can't figure out how to cause it to animate the particles. I plan to generally control the animation from this velocity field, so it is really important that I actually get it working. Any suggestions? I have attached the R&D file I am working with so you can see where I am with all of it. particleTest1.hip
  11. I'm currently following along with Rohan Dalvi's Motion Graphics tutorial, and I've run into two issues with the particles from the outer ring that I thought would have simple solutions, but so far have completely stumped me. The first thing I've found is that each point would spawn two particles, resulting in two lines very close together, and I want to get only one particle/line for each spawn. I've figured out the reason for this happen is that in my POP network I do two separate replicates, each on a different particle stream/group (so that I can have differing life lengths), and the replicate POP passes through the original particles (even those no being replicated) so after merging the replicates back together, I end up with two separate sets of the original spawner particles. Now the solution I came up with was to remove the points I didn't want to replicate, do the replicate for each group, then merge them back together (exactly like I would if I had this issue in SOPs). Problem is though that didn't work at all. I tried both Kill POPs and POP Wrangles, and a few different setups but nothing worked. I've included some notes with the scene file to give better explanations. Secondly, when the spawner particle collides with the tube, the replicator keeps replicating it, so we end up with a bunch of points stacked on top of each other, which I don't want. My idea to fix was to have a node placed straight after the replicate that removes any particles in the "hitparticle" group from the "stream_General_Spawner" group. That way, on the next frame, all the collided particles won't be replicate again. But this didn't entirely work either. "Combine Groups" on the Group POP almost did the trick, but in addition to removing the particles from the spawner group, it also removed them from the hitparticle group, which I don't want because I have a wrangle that does stuff with that group. Does anyone know why these issues exist? I'm guess that I'm missing some sort of foundational knowledge on how POPs work? Any recommendations for tutorials or articles to go along with the documentation to help with this? POPs_problem.hipnc
  12. I think this is prolly an easy answer and I know I should know this. I have a pop net and I have to points enter a group based on the age, and once they are in that group a pop force takes over. but as of now they kinda pop as soon as that force takes over. is there a way to ramp into that group rather than it being an on or off so there is a smooth transaction into the pop force. Thanks for your suggestions in advance!! Rob
  13. Music Visualisation

    More info here: http://simonfarussell.com/The-Creatures-of-Prometheus
  14. Forming object

    Does anyone has an idea of how to do something like this but at the inverse? https://www.youtube.com/watch?v=zrhXB653wKg Any idea would be awesome!
  15. Custom Normal Rotation

    I have a popnet creating some particles with the POP spin, to have a random rotation in each particle, also Im copying a tube in each particle, the tube rotates as it supposed to, but when they hit the ground, the tubes stays with a random rotation as well instead of pointing Y. I'm thinking that if I use the normals instead of the POP spin I could blend between the N0 and N1 when the particle hit the ground, using the hit info from the POPnet, but truthfully I don't know how to achieve this .-. I'm using POPs and copy the tubes/coins to the particles because the particles born magicaly from the floor after a character hit the floor with his cane. If anyone could help me or have any idea I would appreciate it!!!
  16. I have a popnet creating some particles with the POP spin, to have a random rotation in each particle, also Im copying a tube in each particle, the tube rotates as it supposed to, but when they hit the ground, the tubes stays with a random rotation as well instead of pointing Y. I'm thinking that if I use the normals instead of the POP spin I could blend between the N0 and N1 when the particle hit the ground, using the hit info from the POPnet, but truthfully I don't know how to achieve this .-. I'm using POPs and copy the tubes/coins to the particles because the particles born magicaly from the floor after a character hit the floor with his cane. If anyone could help me or have any idea I would appreciate it!!!
  17. POPs: pre solve vs post Solve

    Hi! This is me trying to understand the popSolver in houdini. What is the difference between this two inputs and why they are both wired like that by the shelf (Check the attached image) The particles seems to do the same thing if I rewired as I showed in the second network and they don't do anything at all with the 3rd one. Also why is the wire dotted between the popsource and the popstream, They only work together is both inputs (pre and post) are wired like that. Thanks and pardon my English :$
  18. Popnet Kill

    Hello! I'm trying to kill points inside DOPs (well a popnet actually). The way I'd like to do this is by finding the closest point to the ground object (how do I reference an object in DOPs?) and computing the vector from the POP point to the nearest point, then dotting that onto the ground points normal vector. That's a nice way to figure out which side of the ground the point is on, then killing it. At least that works outside of DOPs. I'm wondering how I can do this inside DOPs because I don't want to post-process kill thousands of points if I can kill them in the simulation. Any ideas? Thanks, cw
  19. Audio affecting particle position

    Hey all I'm quite new to houdini so please bare with me. Is there a way to use an audio output from chops to change the position of a particles? Can I do that by using a pop vop? If so, how can I import my chops output in there and add it to the position of my particles? Is there maybe a better solution for that? Thank you!
  20. Wires on Particles?

    Hi everyone, I'm trying to use the points created by a particle sim, and copy lines to them, then solve them as wires. However, so far I can get nothing to work at all. Nothing ever shows up the in viewport, I don't know why. I have tried using one dop network to create the particles, and another to solve the wires, but this doesn't work. I suspect it's something to do with the fact that the newly created geometry needs to be imported into the DOP network, but I do not know how to do this. Any advice would really be appreciated. Wires_on_Particles.hipnc
  21. POPS

    Hi all, I am trying to use geometry to control attributes on particles. Would anyone know how to do that? Problem. I have a flat bed of sand grains with their "static Kinetic" set very high. But I would like the collision geometry (a hand in this case) to diminish the "static Kinetic" attribute to a very low setting. Much like using the sop solver for fluids. Cheers, dreamagery
  22. Popcurveforce - maxradius attrib not working

    Hey guys! Not really been active here, but planning on changing that I've ran into a little issue and i'm not sure why it isn't working, so I thought I'd try to ask on here. I have some particles following a curve using popcurveforce. I want to be able to influence the thickness of the radius so I made a maxradius attribute on my curve which i'm ramping. I was assuming it would pick up on the attribute but it doesn't. Anybody know? I've attached a HIP file. Cheers! maxradius.hipnc
  23. Get Sop Vel to pops

    I'm trying to find a way to get bring in the velocity from a field i created in sops into pops directly. I can do this easily in dops with a sop geo and a particlestofield node, but i can't seem to replicate this in pops. I've seen this done before in a pop wrangle, but I don't know the code myself. Can anybody help me out?
  24. I thought I was losing my mind when I first ran into this because I thought I was just having a brain fart. But, When using the "Voronoi Fracture Configure Object" I can't seem to only have particles emit from the newly created inner surfaces. I attached my scene file to this post. I know that if I do the fracturing (non-dynamic) in SOPs, I get the inside and outside group. I feel like this is something that is super obvious and I'm just not seeing it right in front of my face. Any help would be much appreciated! Thanks!
  25. DOPs Initial spin at event.

    This has been a very hard search to find an answer to. What I'm trying to do is add an initial spin/rotation to a DOP object. I attached a simple scene of a torus that has an initial upward velocity and then just falls to the ground due to gravity. Essentially, I'm trying to give it a "punch" that will cause it to spin - but not perpetually. A good example would be if you had an object that hit "glass." Although the sim would be physically correct, to add interest it would be nice to add a little spin force to the shards of glass on the initial impact. I can't for the life of me find a way to do this in DOPs. I'm sure I could be overlooking the most obvious parameter, but it's also Houdini and sometime the simplest task takes some finagling. Any help is appreciated! DOP_spin.hipnc