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Found 61 results

  1. Hi, I have an issue that I have not been able to figure out. I need particles/fluid to follow a curve, which I know how to do easily, but this particular curve crosses over itself a couple times so using Volume Velocity and Curve Force causes to particles to divert off by grabbing on to a later section of the curve. (ref images attached) Is there a way to restrict them to the current section they are on so that they ignore the areas where the curve crosses over itself? I have not been able to figure out a way to do it so I thought maybe the amazing Houdini brains on here might have an idea? Thank you in advance for any help/suggestions you can offer!
  2. Smoke follow (fast) animated curve

    Hey Everyone, i'm hoping someone could help me with this problem. In a nutshell, i need to move smoke down an animated path, so that it sticks really tightly to the paths animation, but with all the dynamism a smoke sim brings to the table, i.e. nice peeling away around all the edges etc - I have a fairly fast moving alembic curve - cached out with 10 substeps. (may not be needed but there if i do) - I am using pops with curve force to fire particles down the path, so they follow the curve closely. - Then im using the particles to source density, and also adding their velocity into the sim so that it makes the smoke move along the curve. - Im using a high dissipation value so that i can tighten up the expansion so you can really get a sense of where the curve is / maintain the shape. My issues lie generally in 2 places: 1. Where the animated curve is moving the most - the smoke / velocities struggle to catch up and i end up with a hard edge. 2. Where the curve is tangentially facing inwards in relation to the curve, the velocities 'add' the other way, also creating a hard edge. To try and illustrate what im after - if i could animate a regular smoke sim down a straight path and then warp it into an animated spline shape / spline wrap effect, this would be the best way to achieve it, but im really not sure if is possible - hence this approach. I have already tried upping substeps - but it didnt make any difference. My gut feeling is that the problem lies within how i am sourcing the velocity. I will point out that i am very much in my houdini infancy, so my ability to problem solve isn't great (yet!) Has anyone worked on a similar effect before, or does anyone have any tips/tricks/tuts on how to achieve what im after? Any/All help very much appreciated! Cheers, C SmokeAlongCurve.mp4
  3. Hello, I have an object what I broke with an rbdmaterial fracture then I feed the points into a popnet and add some stuff like wind to move the points. My question is: How can I reset or rebuild or move back the points into their original place and shape like a fast rewind or something. Thank you
  4. Hi I'm trying to use the instance object to make different spheres on my different POP groups but whenever I assign the Instance to a specific group I get no result. Only works with no group specified. Surface Advect Final.hiplc
  5. Hi, Does anyone know how to create variable friction for collision geometry when using particles In houdini. In maya or realflow you can create/paint friction maps. I was wondering what the houdini workflow is to create this. Thanks in advance, R.
  6. How to Transfer UVs to Vellum Grains

    Hey, has anyone tried this yet? In the past when creating FLIPs I would normally carry UVs through DOPs using an attribute promote to carry the UVs from vertices to points, but it seems like this is not working when applying the same methodology with vellum? Please help!
  7. Hi Everyone I am trying to replicate the output of this tutorial in houdini which was done in 3ds Max by Allan Mckay i am trying this thing in houdini since weeks but i am no way near to that......... A little help would be appreaciated!!!!
  8. Hi, I am trying to create condensation or water dripping over the surface, something like this, but so far i am totally unsuccessful. A liittle help would be appreciated
  9. Stylised Trails

    Hi Guys, I need a little advice. I am trying to create trails that have a look similar to the image below. My initial thought was to scatter points on a circle with an initial velocity and then advect them through a volume using curl noise...before using an add sop to group by id (Hip file attached). I am having difficulty trying to replicate the look and feel of the trail animation in the video below at 0.24. The trails appear very wispy and almost fluid like. If someone can help point me in the right direction that would be greatly appreciated. Many thanks, Clive Test_Curves.hip
  10. 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.
  11. 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
  12. 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!
  13. 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?
  14. 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!
  15. 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
  16. 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
  17. 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
  18. 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
  19. 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
  20. 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
  21. 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
  22. Music Visualisation

    More info here: http://simonfarussell.com/The-Creatures-of-Prometheus
  23. 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!
  24. 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!!!
  25. 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!!!
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