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Found 407 results

  1. Fluid Along Surface

    Hi Guys, I'm new to Houdini so please, bear with me:) So, what I want to achieve is following: I want to have fluids (or particles, through POP Fluid), that would go up against the gravity (antigravity) along the collision geometry, upwards, along the vectors that are parallel to the surface of geometry. The effect should look like a paint going down on a surface, and covering it, but the direction is reverse, so it goes upwards. The collision geometry is simple, like a sword, thats it. I tried to do it with flip tank, with attraction force, but somehow I couldn't not get the result I was hoping for. Can you please show me the direction I have to follow or an advice I can follow to achieve this result? Is it better to do it through Flip or through particles? Thank you in advance. Cheers, David
  2. Hello everyone, I am a new Houdini Indie user, so i might have missed the obvious. I am exporting a particles explosion from Houdini to Unreal. it works great except for the trail node. It does export the datas ( file is much heavier with trail node) but the trail node is duplicating the particles id ( and probably all the other attributes). Once I import a cache in Niagara, I only see the particles from the POP and not the one from the trail. I tried randomizing the id attribute on a static particle system, and the trails points do appear properly. ( on an animated one it juste pops a random particle every frame). I was looking for a way to either, give the trails points an id or create a trail directly within my popnet. For the second option i basically want to pop a particles every frame with a 1frame life from each points of the simulation... but I cant find how to do that. Do you have any leads to what route to take? thank you!
  3. I'm sure there is a simple answer for this, but it's got me scratching my head... I'm trying to use the @hittime attribute in order to do some stuff with my @pscale, but it never stops growing even after the particles are stopped by the pop collision detect behavior. The @hittotal attribute does the same thing, like they are all vibrating on the surface or something even though they are not moving. I've attached a simple scene. pop_hittime_1.hip
  4. Alrighy, I have a big wedge of stupid in my head that is keeping me from doing this. I have particles emitting into a container (a super-simplified version is attached). I would like to get it where instead of the usual bounce/slide off a wall, the particles slow down and gradually move/are pushed away from the containing walls. I'm assuming this would be done using SDF/volume sample/volume gradient and a POP wrangle modifying the velocity based on the sampled values, but I just can't get it to work. I've seen lots of tutorials on using this approach to get particles to stay NEAR a surface, but my brain isn't adapting that to a nudge-away-from-a-surface instead of a nudge-towards. What am I doing wrong? The POP wrangle code-in-progress (the collider is input 2, the VDB is input 3): float samp = volumesample(2, 0, @P); vector grad = volumegradient(2, 0, @P); @v *= -grad; SOMETHING is happening, just not what I want. (And ideally I could have a second SDF inside the container pushing out, thus gently keeping the particles within a certain radius of the container wall, not going to the center.) Thanks for any help! example.hiplc
  5. fun and play with particles

    having some fun with particles.... birth of a massive star. for my little #astrophysics exploration, i’ve created a star simulation using openCL in houdini. its based on nbody #physics model, only driven by #gravity. using #nvidia #quadro rtx 5000 #arnoldrender. the colours are not quite right, I am trying to integrate kelvin colour temperature. the current colour is based on density and speed. In this simulation, I assumed 48% amount of negative gravity to fill the mystery of dark matter. I used 1 million nbodies for the simulation. for the steps, I am planning to add finer particle streams to get more details. fast particle rendering with path tracer is hard !
  6. This is my first post in the forum, so first things first: Hello everyone!! Down to business: I'm trying to create a custom 3d vector field from a set of imported lines so I can drop some particle tracers on it. I managed to convert the imported lines to vectors using the orient along curve node, and I also created some voxels through bound>volume (ideally one for each of my imported lines, although I'm not sure I succeded). Now, what I want to do, is to link each one of my custom vectors to it's correspondent voxel, so that when a particle is inside that voxel is affected only by that particular vector. This is where I get lost, I don't know how to link my vectors to my voxels... I tried importing my "vec" point attribute inside my volumevop but for the life of me I can't seem to figure it out. I come from Rhino+Grasshopper, so I thought I'd be a bit familiar with the node workflow and all but... wow... Switching to Houdini feels more like stepping off a meek pony and jumping right on top of an untamed pissed off stallion. I'm attaching my files. Any help taming this beast will be much appreciated (Probeta_02_vF_S.igs is the file containing the custom lines) Custom_vField.zip
  7. Fluids - help!

    Hi team! I have followed a good tutorial on Youtube as I was having issues with keeping fluid in a container, this tutorial also shows how to do bubbles in the water ( Tutorial here ) When the bubbles go through the water there is a loss of fluid and I have been playing around a lot trying to figure out how to prevent the loss, when the collision objects aren't connected there is no loss in the amount of fluid but when I connect the Collison object there is a loss of fluid and I cant figure out how to stop that. I was wondering if anyone else happened to know? Its just bothering me and I wanted to know the answer. Cheers! Hottub.hipnc
  8. Using Engine I have been able to import a particle cache into Maya just fine. Scale and color came through and were easily applied in Arnold. However, I need to recache the particles as a Maya nParticle cache to hand it off to someone else not using Houdini Engine. I can get it to cache the general position/lifespan, but it doesn't appear that any color/scale(radiusPP)/alpha(/transparency) information is in the re-cache. How can I make sure those attributes make it through to the nParticles (re)cache? Thanks for any help!
  9. Redshift instances shaders

    Hey guys, i have a question regarding redshift instances on high particle counts stuff rendered with redshift: Everything is working well with a "s@instance=..." wrangle. Then if i try to get the Cd attribute to change the instances/particles color it get super slow, is it a normal behavior or is it somehow a way to avoid it/doing it more efficiently ? For example if i don't use instances but standard redshift particles, even with changing the Cd in the shader it is super fast, it only happens when instancing.
  10. In a pipeline that requires you to do VFX work in Houdini and then render said VFX in 3ds max, there are many formats that are viable (I mostly use alembic). But I was not lucky finding a straightforward method/format to export particle systems that were created in Houdini to be later replaced by geometry in 3ds max for rendering. After some tests, we managed to do it using an HDA called PRTRop which exports particles in .prt file format. The particles were then imported into 3ds max using TyFlow, that reads a couple attributes such as width (pscale), id - this one is necessary for tyflow to import the particles, velocity, etc... Then we hit another roadblock: what if I want to export particles with orientation information for my geometry instancing? It turns out that, after some more testing, we discovered Tyflow uses an attribute called Orientation (case sensitive) which is a quaternion just like Houdinis orient attribute, and it has to be exported as a float16. So in case some of you were wondering how to do this, I'm sharing the workflow used here. If some of you know a better way feel free to share it... it might save some lives! Cheers, Mozzo
  11. Lets say you use c4d and you instance an object into different particles (with random rotations for example). If then you export that instanced geometry as an alembic and import it in 3ds max you get geometry with world transformation information (each geometry instanced has its own rotate/scale/translate info). Is it possible to do the same in Houdini?
  12. Emit pyro outwards (not upwards)

    Hey everyone, I have an animated object moving in a sin wave type motion. I am trying to emit smoke outwards from it. At the moment the smoke is just rising in Y which isn't what I want. Any suggestions? + i made an awful unnecessary diagram, it might help or it might be confuse matters
  13. Hi, I have some particles stick on an animated object, wherever it goes the particles keep their position. Now, what I need is these particles to "walk" on the surface of this object like they were insects. How can I achieve this effect? Thanks!
  14. kill by velocity

    Hey guys! I need to kill particles that have little/no movement. The trouble with killing by velocity is the particles that are moving, are varying in the axis they're moving in so I can't just kill @P.y ? Any suggestions? Is it maybe possible to get each a particles speed of some sort?
  15. Hi guys, I would like to know if there a better way to do this kind of powder stuff with a lot of detail (like the picture) than grain simulation because it's really heavy.. Thank you.
  16. right vex code for velocity to particles

    Hello, I am thinking that I've forgot the vex code for giving birthed particles some velocity... I have used this code to give some velocities to the particles... @N = @N @v = @N but now I am back at Houdini and I have tried it again and somehow it isn't working anymore... And how should I start to achieve the result like in the video? I am trying to get the main explosion burst on the torus so that I can use the same way to my already modeled falcon 9. There is a "ring" of smoke which I like to replicate to my torus... The air explosion from 0:18 to 0:22 I would be very glad if someone could help me Thanks in advance (
  17. So this seems like a silly question but I am trying to emulate a population with particles. I have male and female particles. When the female particles gets to a certain age or greater, a "popreplicate" triggers and "baby" particles is made. The issue I am having is the baby particles seem to die 1 frame after their mother particle dies. Ignoring the life length I set on the popreplicate, even if its set to 100 (seconds) . They don't seem to have an equal life of their own. What am I doing wrong?
  18. Hi, I'm quiet new in this big world of Houdini, i need help. The project consists of creating spheres on the points extracted from a pop simulation and then destroying them. The problem I encounter is that when I put the glue on different spheres it seems that it creates the glue on all the broken pieces. It could be the fact that in the assemble node, it considers those points as a single geometry, but I don't know how to divide those points as unique entities and then apply the glue only on the individual spheres and not on all of them as a single object. Thank you in advance for your attention and any help. I attach the file below. Thanks a lot! Fra_pop_copysphere_and_rbd_.hipnc
  19. Hello everyone! I recently made a setup to achieve magical smoke effect that orbits while moving. I shaped and animated a bunch of points that move along a custom curve. I want to make all those points orbit or twist around the original path (curve), something similar to curve force node for POP. I'm having some difficulties making this happen with VEX. I would appreciate your help. Cheers; Basic Shape.hip
  20. Slow-motion Tire Burnout

    Hello Guys! I´m having a little trouble with a scene and was hoping you guys could help me figure it out. I´m trying to recreate this tire burnout effect. not the classical, lots of smoke everywhere, but this simple and detailed smoke. https://therealmarky.onfabrik.com/portfolio/audi-r8-spin at the moment I´m emitting some particles at the tire contact with the ground, and using them as an emitter for the smoke. The real problem comes with the slow motion. I´ve tried retiming the sim, but it wont match the animated car. I´ve tried doing the sim at the origin. smoke looks better, but its noticeable how it is moving across the scene. I´ve tried taking the time scale down to 0.5, 0.1, 0.05, 0.025. the sim slows down, but it obviously looses all the details from the microsolvers. My question is, how would you guys attack this kind of slow-motion shots? am I in the right track with the pops and timescale? Thanks a lot in advance!
  21. Hey everyone! I am try to simply advect particles with a moving object. We have particles/grains floating around and a person runs through them at speed so I just need to create some advection/turbulence, more than what's already created from the collision. I assume it is as simple as pyro but I can't seem to work this one out. Any ideas? Thanks
  22. Does anyone know how to rotate an object around its velocity vector while it is still pointing into the direction of its velocity in vex? Maybe it is easier in vops, but it would help me understand better the underlying math behind it with vex.
  23. Hi everyone I dont know if is it possible in houdini vellum grain to increase the actual number of particles coming out of a vellum configire grain constraint? That way one can control how much grain is coming out the the vellum grain Thank you
  24. EDIT: Just doing a clean up; So I'm looking to import CFD data in order to drive a particle simulation in Houdini. So far I've managed to import the data through the Import Table Node. Get position values from 1 ID Group according to all ID's and even for one instance animated a sphere along the point positions of 1 group. 1 ID value. Does anyone know where I should be going from here? Which node groups I should be looking at? What would be my ultimate goal would be to use this data tot drive a particle simulation, eg each id relates to a particle and it moves along the corresponding positional and velocity information contained in the CSV. As always any and all help is greatly appreciated. Kindest regards, Chris Particle_Test_CFD.csv
  25. Popspin not affecting orient

    Im currently working on a tracking rocket system. I have an orient created from the velocity vector. Why does the popspin not affect the rotation? It has something to do with the popvop where I make the orient. Also does anyone know a way of creating an orient attribute using velocity in vex? Many thanks. FXTD_016_PARTICLES_rocket_system_001.00_ark.hipnc