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Found 138 results

  1. Hi, I'm a beginner in Houdini learning alone with tutorials, I need some insights about POP. What I'm trying to achieve: I want to reproduce this effect, but slower: Basicaly, I have a polyline forming a shape, I scale each primitive in a foreach loop with x iterations. Each iteration go through a DOP Network with a different seed based on the index of the polyline in the for loop. The DOP Network move points with a curlNoise, I then create a trail. The screenshot shows the effect on a single instance. Questions: 1/ I can't access the Birth Parameters on the POP Source node. From the help, it seems "Impulse Activation" at anything but 0 to be able to access those settings, but it's greyed out. Am I missing something? (It's greyed out even if I input "1" and not an expression.) 2/ To get a lower number of points, I used an Impute Activation of (($F%20)-1)*-1 == 1 point every 20 frames. The problem is that now, the DOP network does not begin before $F=20. Is there any other way to tell POP not to birth points every frames while being able to choose the first birth frame? 3/ I want each point created in DOP to keep as an attribute his original position (when his age was 0), and I want each new point to keep @ptnum of the source point as an attribute. How can I do that in DOP? Thanks!
  2. Hey Everyone! Is it possible to define a region (perhaps with a shape) which pop forces are applied. I have an rbd sim and am looking to have a specific area that is affected by a pop force. Any ideas? Thanks
  3. Particles will bounce off a collision object, and I can influence that using the collider's Bounce parameter. Great. However, if I change my particles to grains, they will not bounce anymore, but slide. No matter what I do and this goes for pop grains as well as for Vellum grains. Settting ispbd to 0 is not a real solution, as this means I am not using PBD/Grains, anymore. Any idea? Here's a very simple test scene, using a pighead. Just activate/deactivate the POP Grains node in DOPs. collision_grains.hipnc
  4. kill pop force contribution on Y

    hey! is there a way of limiting or killing the contribution of pop force in an axis?
  5. Hi, In my popnet, I want that, a new particle is born only if there are no particles in the scene. That is, suppose a single particle is born and dies after, say some random frame, only then a new particle is born. No new particle can be born even if a single particle is alive. How can I do that? Please help Thanks @Alain2131 : Sorry to tag you here, I just wanted some more help. Please let me know if tagging is not permitted or if you are bothered by it, I wont tag you again.
  6. 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
  7. Underwater Bubble Sim

    Hey guys, so basically I'm trying to replicate an object dropping into a tank of water splash but with the bubbles/water only. The way I'm currently doing it is by emitting particles based on emission attributes defined on the surface based on it's velocity and using vdb from particles to mesh the liquid and so far it's alright. However, the client wanted a more art directable look towards the pop sim whereby more lengthy/streaky bubbles instead of huge splash etc and it got me thinking how can I achieve this? I'm on H16 and there's no pop fluid where I can easy increase the surface tension and viscosity to save my shot. Is there any pointers on hacking this shot without doing Flip? I'll upload my WIP, files and other references from client tomorrow. Thanks
  8. Duplicate objects in RBD pop net

    DOP net question. I want to start with a set number of boxes and have them move around with POP forces and bounce off each other with RBD. Problem is that I end up with two items for each one I put in. For the POP source I setup Impulse activation to be $F == 2. If I use 1 there, I only get one set of items but they aren't effected by the POPAdvect forces. Feels like a rookie mistaken, but I not sure how to set it up. Any ideas? POP Source: Emission Type is All Geo, Geo Source is First Con text RBD Vector Field.hipnc
  9. hey everyone, I'm struggling with a problem. Here, the particles move randomly. I would like them to become visible when they pass through the cone until it comes out. I don't know how to proceed, I tried a few things but couldn't get something to work. How should I create the collision attribute and apply it to my attribute vop ? Could someone help me or guide me a bit, please. Thanks particule_collide_dust.hipnc
  10. Hey all, I'm trying to get a better grasp of best practices for managing substeps between two separate DOPnets. I have a DOPnet that takes in moving geo and outputs particles, which I rasterize to a volume, then source into another DOPnet as fuel, temp, etc. for a pyro simulation. What I'm wondering about specifically is how to keep these two DOPnets in sync. i.e. I want to make sure only newly generated fuel is sourced into the pyro sim, not fuel that's already "burned". My concern is that if the POPnet creates particles with life longer than a substep on my pyro sim, they will be copied into the pyro multiple times. It seems like it would be best if the particles and Pyro were created in the same DOPnet? I don't know enough about how any of this works though.
  11. Custom attract

    Hi I am trying to create a custom attraction tool using popvops. Its a method I learnt doing a houdini course I would like to improve on it but I have been stuck on it forever. Instead of using a pop attract we are using a popvop to calculate the distance of the particles to a point in space and making them move to this point, if I am using a single point to attract them to its working fine, but what I would like to do is to attract them to multiple points ie a mesh. I have tried using the importpoints but that just makes them go to origin. I would like them to move to the rubber toy. Any advice would be appreciated. I have attached the file and the particle stream I am using to test. Cheers Particles.72.bgeo.sc attraction test.hiplc
  12. I have a feeling this might be a dumb question, but I have been stuck on it for a few days now. Or maybe not so, as I've been looking countless treads here, but none really solved my problem. I've got a really simple setup, pop curve force guiding some rbd objects (I also tried doing it with points and copy stamping after sim to the same result). At a point in the sim the vectors start to point outwards: What I would need is for their direction to be always facing forward as they are at the start: I've had some luck with using pop torque, but still not what I need. I've attached an example file and the curve alembic. RBD_Directional_Vectors_Curve_Force.hip curve01.abc
  13. Dear community, I am working on a little particle system that I need some help with and I hope that you can help me out somehow: I am emitting particles from points A. These particles are attracted by another pointcloud B via POP Attract, with the attraction type set to points. So far so good. My question is now: How can I vary the attraction force inside pointcloud B for each point? Is that possible? I've been looking into and reading the docs, of course, but all to no avail. Does anybody have an idea on how to solve this issue, meaning giving the points in pointcloud B varying attraction forces? Is there an attribute that I have to apply on pointcloud B, that POP attract could use? Best wishes and merry christmas and Chanukka, Nicolas
  14. I am trying to blow up multiple groups of particles in a sequence.(boxes of confetti exploding at different times). The activation isn't really the problem as I can use a sop solver within a dop to activate the particles group at different time. The issue is to give them that "initial velocity" at activation time. The only method i found that is working to achieve the effect, was to actually import and merge many popobject and "activate" them one by one in a sequence , with the velocity attribute created at sop level This solution is of course very inconvenient. I attached a clean file, with just the different group all popping at the same time. a solution to have them delayed one after the other would be very welcome I just can't find an elegant method which works procedurally. Thank you for your help confetis.hip
  15. **I'm amending this--originally it was just the below question, about making POP particles collide with FLIP sims, but I just was toying with multiple POP emitters/particles in the same scene, and they don't seem to want to play together easier--so my more fundamental (surely stupider) question is: how does one make different particle systems (POP, FLIP) interact? For instance, in the supersimple screenshot, I would want the orange particles (which have initial velocity on x) to collide with the blue ones. I would think, since they're part of the same POP solver, this would just happen. I would think wrong.** I have a puddle of bood, a viscous FLIP fluid. I have POP particle rain (a la https://www.sidefx.com/tutorials/rain-systems-and-wetmaps/). How can I make the rain (the particles--I assume not the instanced geo) collide with/splash the FLIP fluids? I understand how to use POP forces on FLIP sims, but when I put a POPnet and FLIP sim in the same scene, they just ignore each other. Since static/RBD and particle (FLIP or POP) solvers all play so well together with minimal extra effort, I'm sure getting POP and FLIP sims to play together is something simple and dumb. Thanks!
  16. particle trails fading

    hey! sorry for the dumb question, but I couldn't find an answer I have a pop sim with some points, and I'm trailing them with the trail/add combo, it's all good but I can't find a way to map Alpha or color to the length of the trail to let the trail fade away, any idea? cheers!
  17. Hi everyone, Can anyone figure out how to do this stuff? I have tried many different ways but cant get it achieve the similar result. Down below are my approach, didnt really get colliding and sort of stacking effect.
  18. Crowd tilt avoidance on terrain

    Hi, I have little agent insects on a rock, sitting on flat ledges. I'd like them to wander, while avoiding steep slopes of the terrain. Does anyone know the best method to go about this? (FYI I'm fairly new to crowd- I was imagining I'd need a pop wrangle to use a look-at function, which would estimate the possible future tilt, then apply an avoidance force.) Any help is much appreciated!
  19. PARTICLES MOTION STOP

    HI, I know this might be an easy thing but i tried out and seems like i'm making a silly mistake. How can i make the movement of particles stop as it slows down?
  20. WATER DRIP

    Hi, I've been trying to make particles slide down a vertical surface but I want them to stop for a second while in motion, and then continue sliding again. I guess, I badly need help with this. Can anyone help me out ? I've tried animating the response feature in POP Behavior Detect but didn't work out. Each particle should have its own movement. Regards, David
  21. Hi, I want to emit particles from an texture just like in maya. I find the old thread here : but in houdini 16.5. That seems not work. . there are no " birth probability ",but "emisson attribute".And it says that it will use a point attribute.(but this will need very high mesh resolusion.) I fill the pic function in it ,but it returns an error. How to do this ? Thank you very much.
  22. Recursive Particle Split

    Hey guys, how can I duplicate particles recursively? Sort of in a fractal / l-system way, to simulate veins, bramches and stuff like this Thx
  23. Hello there, Is there any way to create Geo dynamically inside a dopnet? Specifically, i would like to have growing tendrils, and simulate those as they are created using popgrains. I created a popwrangle inside my dopnet, and created new points and primitives through vex. Unfortunately, that breaks the pop solver, as its not solving the newly created particles (However, if I put a force after the popsolver it works). I thought maybe that resetting the id to -1 (as used in a similiar way with the bullet solver) would do the trick, but unfortunately not. Is there any way that I can force the popsolver to recognize those newly created particles? Thanks in advance, Bajt createGeoinPop_v01.hiplc
  24. Points follow points

    Hello everybody! I would like to simulate particles on top of pre-animated / pre-simulated (cached) points. So far I only managed to do the "transfer v attribute inside a sop solver" trick. Unfortunately it does not give me the result I imagine. Instead of inheriting only the velocity I would rather like the points to be attracted by the pre-animated points so they tumble around and follow them the animated ones. Basically I am trying to animate some points and then do a simulation on top of it to give it a more natural feel and to be able to art direct the simulation better. I would greatly appreciate if somebody could give me a hint or a solution on how to do that? Thank you! Here is my current progress (particles inherit v): pop_transfer_vel.hiplc
  25. Pop Collision Ignore + Grain Solver

    hey guys, is there a way to make the Pop Collision Ignore node work with the grain solver? I really need to avoid the collision of one granular solid object, it works fine with normal particles but not with the grain solver. grains_avoid.collision_1.01.hiplc
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