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Found 65 results

  1. Hello, I was wondering if it's possible to create velocity vectors from an animated sequence (texture). Ideally something similar to Optical Flow. I can extract movement from geometry (eg. use trail to generate v vector of animated VOP) and I can do basic image analysis (eg. convolution kernel operations on coloured points using VOP) so I feel it could be kind of possible to do it but can't get my head around it. In terms of results I'd like to create a particle system that reacts to an animated texture (eg. overlay particles on a animated texture and have them follow the movements in the video) thanks!
  2. Hello, I'm trying to get a logo to dissolve/disintegrate into sand. Like it is made out of sand and something is eating out the outside shell and the sand is pouring out. In the attached file I was first trying to use a geometry and use attribute transfer to set the force of a popforce. as I would like to use in the future a more random/noisy pattern. I'm not exactly sure if my expression is wrong, if my whole set up is wrong. I tried to look around for tutorials or thread but couldn't find any. Any idea, suggestion or links would be greatly appreciated. thanks bil Sand_Desintegration01.hipnc
  3. Hi, Let's say I have a bunch of points that I have created, and I want to treat them as particles in a popnet - how do I do this? Is it possible to do this without emitting from the source points for one frame? I noticed that you can set the initial geometry for the popobject node, and gravity and forces do effect these points, but no pop nodes do anything at all. How do I get the pop solver to consider these points as particles? I have attached a simple example. (Note: The popsource node has the Geometry Source set to 'Use DOP Objects', but this is undocumented) Points_as_Particles.hipnc
  4. Hi does anyone know how can I add a hard constraint between two or more particles ? exactly like RBD objects but it should be work for POP solver. I prefer do this via custom VEX codes for manipulating P or V. Thanks S
  5. Hi guys, I've hit a bit of a wall in the new version of POPs. I have a deforming mesh (skinned character), which I have scattered points on. What I'm trying to achieve is a set of particles that are essentially locked onto their source point until a certain time or proximity from some sort of gizmo, and then morph to the position of another set of points. I have been able to achieve this in the old version of POPs using a position node, but it's rather slow. However I can't seem to figure out how to achieve the same thing in the DOP version of POPS. Any help would be great appreciated. Thanks
  6. Hello, everyone A simple question, it's basically the title. By "increase" I mean increase by a lot. Everything the same, just turning on "Use deforming geometry" increases the sim from 60 frames in around 8 hours to 7 frames in the same time From what I could see it really takes a long time in the "creating collision mask" (or something of the sort) step. I have the VDB of the colliding object already cached in a SSD. So, is this normal? Also, a side-question, when you use a static object in DOPs, does it use the Bullet Solver or the RBD solver by default? I'm sure I saw this question here before, but unfortunately I can't find it
  7. Hi everyone, I try to figure out how to retarget a vector (v in that case) in particle trails. I explain: i got master particles who trail other particles in space, i inherit the master "v" to achieve a motion blur at render time, to avoid to much substep that way i got smooth line at low calculation cost. but i need to slightly noise the trails to achieve a "moving tentacles" look. Here is the problem when i apply the noise, obviously my "fake" v vector is not aligned anymore, it's stepped... i tried to recompute the vector with the help of id, but since my emission is not constant ( i shot on frame 5, frame10, frame15 etc..)the incrementation of the id in not constant to...I tried basic vector arithmetic, but i don't get results i need...I join a hip file, does anyone got an idea??? thanks by advance. Best H PS:excuse my english, I'm French... RecomputVelTest.hip
  8. Hi, I create a new project but have a new problem. use to source object its has not problem but when added the point on source objects its changing rotation. I hope, you can help me for ı can fix my files.
  9. Hello, I'm trying to control some particles, I need them to travel on a ground, toward an object, then creep up on that object surface, when they reach it. I've tried a few method (creep, ray, slide on collision ...) but even if I manage to have them slide on an object surface, my problem is how to set up the POP network in order to have them transitioning from one surface to another. I've cheated with a P.y = 0 in order to have them on the ground with ease, but I'm failing at controlling a nice transition from ground to object. here is a basic setup, without much, in order to not restrict the different approaches . Also, I'll replace the particle with a small disk later, so I think I need them (particles) to be oriented properly. Thanks for any advise and help! prtcl_slide_4OD.hipnc
  10. Hello everyone ! Does someone know how to use an animated mesh for driving some velocities of particles ? I have done a sim that I like but I want it to follow the character's animation... The particles born in the chest and goes to his head which is rotating... I'm pretty new to pops, I think that maybe I can make it move through a pcopen but maybe it is a bit too much for what I want to do ? Also, I'm not pretty sure about how to make it... Maybe it's possible to feed the pcopen with a scatter of point on the surface of the character ? Thanks a lot and have a great day ! (Once finished and online I will try to post it as a comment !)
  11. Hi all, a question about doing vapor trails (contrails). I'm looking to do a contrail from an engine of a jet, and the method I'm using is 1. Do a pyro sim, and cache out a single frame. 2. With POP network, birth particle points with attribute $AGE 3. Using copy SOP, copy the cached out single frame of the pyro smoke onto each point of the points from POP. 4. Create alpha attribute on the POP points using the expression I found searching on this forum on a point SOP, as answer provided by member Wolfwood; 1-smooth($AGE,2,3) Now this works well on the Points, as the points fade out to 0 alpha and disappear after 3 seconds, but since I'm copying the static single pyro sim a (.bgeo) on to each of these points, I want the volume to have the same behavior; that is, after 3 seconds, completely disappear. Of course, since I'm copying the volume onto points, when points die after certain number of seconds(say, 6 seconds), the volume that has been copied onto the point also dies, but it's not gradual, rather, it just dies suddenly without slow fade to zero alpha. So, the question is, what is the best way to transfer this slow fading of alpha attribute onto the volumes? I thought about using the expression on the material' density, but then the entire volume trail fades together, whereas I want the volume to start fading few seconds after they're born, that is, the volume furthest from the traveling jet's engine fades first. I hope this makes sense and I would appreciate any insight. Thanks!
  12. As nobody answered my previous post (no hard feelings ), here I am again. I have made some progress with sand/grain but I'm still not sure of the process. In this new file I'm trying to have the sand to gradually blow away . I'm using a PopForce to move my particles and I'm controlling the v@Force Attribute with a voppop. I'm using a ramp based on Y and a turbulence noise to set the @force value as I would like the sand to start blowing randomly from the top and slowly go down the pile of sand. But I have 2 problems. 1- because the noise and the ramp are based on position, the particles enter and exit the noise/value 2- the noise is fading to quickly, I think I need to add a fit node to compensate.. but I can't figure it out. Here is my ramp/noise test (on a volume). PS: my previous post was about sand disintegration. and I attached a Hip of my scene. Please Help me out! sandtest_forceRandom.hiplc
  13. Hello I need to deactivate a passive collider at some point in my sim, and I can't figure out a simple way to deactivate it. I've tried groups, affectors, 'active value'. It's probably a simple fix, but the only 'hack' that I've found is to use a merge under my static object (merge with a null) and keyframe its activation between 1 and 0 Thanks in advance Bernie
  14. Hey, I'm trying to create blow effects for my particles which will be snow. At this moment I have smoke advect which drive my particles but it still looks really bad. I would like to create light snow/grains like a dust which will unhide object after blow. Fox example: ball is hidden under the small amount of snow and someone blow this snow using mouth to unhide this object which is under it. hope it is enough clear to understand what I mean. advec.hipnc
  15. Hello, I am dealing with a particle sim and I need some way of optimizing it. This is the case: particles are emitted and falling on the ground. Once they fall on the ground they bounce a bit and then stop moving. In this simulation I need to emit a lot of particles so it goes slow after a bit as particles accumulate fast on the ground. However I don't need to simulate those particles on the ground anymore, but pop solver simulates them all. Is there some sort of equivalent of @active attribute as in bullet sim? I can think of one way - I can set up a velocity treshold, which will move stopped particles to a group. Then I can remove particles from this group so that pop solver doesn't simulate them, but before that I will collect them in another solver? Any better approaches / ideas? Juraj
  16. Hey guys, Hopefully this is a quick one. I was wondering how I could find the average position of a group of particles (and store the position as an attribute on the particles in that group)? Say I have two groups, A and B, and I want to find the average position of the particles in group A and create a force on the particles in group B to go towards that point (center of A), and at the same time have all the particles in group A move towards center of B. POP Group A -> Center of POP Group B POP Group B -> Center of POP Group A Thanks
  17. Hey guys, First post so go easy! But I was wondering if there was a way to convert the wet sand POP grains I've made into a volume by creating the vdb from the points generated by the sand? I've had a look around but can't really seem to find anything on it. I attached my .hip, its pretty straight forward, but the idea was to get the sphere to slice in half, but then recreate the geometry from the volume. Thanks split.hip
  18. Hi All, I am trying to implement a concept of a spool of thread that unwinds leaving a trail that then takes on the shape of the classic "support this cause" ribbon. I have started with Matt's Pop Trails example file and replaced the scatter with an Object Merge of a single point from an external object that tracks the spools Z position. This gets me a single thread trailing the spool. What I don't know how to do, is to make the trailing thread take on the proposed shape for the concept? Is this Pop Trails example the best way to handle this or is there a better approach? Thanks ap_me_pop_trails_spool_thread.hipnc
  19. Hello Everyone, I am rookie in houdini and currently i`m struggling in making a gun impact system in houdini, which should have a characteristic to make dents according to the properties where the bullets like metal, concrete wall, brickwall, wood etc. Please help me. A help with a hip file will be nice and helpful more to me
  20. Ok, so this is about me (and anyone else interested) learning how to manage particles in groups/streams and I'm going back to the type of growth I've done before, stacking POPs, but never managed to get working in one single POP network. Basically, the groups and/or streams just don't act as I expect them too, I just don't "get it", how the streams/groups are handled through the solver cycle... So this is what I came up with, because if I understand how to set this up, I know I "got it" - so to speak. Here's the "rules". Blue particles are born from the orange input point on the first frame. Blue particles create a trail of red, static particles. At a random interval, blue particles replicate a pink particle. Pink particles create a trail of green, static particles. Pink and blue particles avoid the static red and green particles. Pink and blue particles also travel through a noise field. The noise doesn't affect the red and green particles. Oh, and the colors aren't just descriptive, they should have these colors. And it all seems so simple - if I still was in Max, I'd be able to set this up in PF or TP in 10 minutes - but getting this going in a single POP, I can't even get half way before it "breaks", thus the very basic hip file. No reason to supply the 15 ways I failed to do this... splittage.hipnc
  21. Hi guys,i have 2 problems with the ip,first i can't group particles,the advect by filament keeps affecting all particles I want to affect just the one near the emitter Second the mesh that its used by the source filaments node collides with the ground ,there is a way to ignore this collision? Thanks! AdvectByfilament.hipnc
  22. I scatter points on a surface and then bring them into a DOP network to do some dynamics. I would like to create clusters for some of the particles, to get bigger chunks at some parts, rather than individual points. Initially I tried to pack some of them before bringing them into DOP, but it seems that the popsource1 node removes any primitive data, so no packed geo are coming out of it. I am not trying to figure out if I could use spring constraints to force some particle groups to stay together. Has anyone done this before? How would I go about combining POP forces and SBD or RBD spring constraints ? thank you georgios
  23. Hey guys. Quick question here. I have a simple particle sim emitting from a sphere in a direction. I want the velocity to decrease as the particles get older. how would I be able to achieve that? Some of the particles are already born at frame 1 (I have a preroll on my sim) and this needs to apply to them as well. Thanks for the help, and thanks for an awesome forum. Cheers
  24. Hey guys, first post here. I'm extremely noob at Houdini and I've got a very basic question. I've got a particle system going, and after the POPs system in the Source Particles SOP it creates, I'm trying to use the Y position of each particle to drive a Blend Sequence that is copied onto the particles with a Copy SOP. What I haven't been able to find is how to query the Y position of my particles. I can find their positions with the Geometry Spreadsheet, but the name of the attribute it gives me is "P[y]", and typing that into an expression doesn't seem to work. I had thought it might be "@P.y" but that errors out as well. I think one of the problems is that I'm not telling Houdini WHAT to find the Y position of. But again, not sure how to find that. I've googled and did a cursory search of the forums here but all the posts I've found are way more advanced than this simple thing I'm trying to find Can you fine gentlemen/ladies point me in the right direction to find how to query this sort of basic data? wk2_copy.hipnc
  25. Hello guys, I work whitewater for splash. I made a whitewater source particle. I want high velocity pariticle delete. So I made a high velocity group made. However, The pariticle are removed from the group while slower speeds. For example is parabolic movement. But If I want to continue to maintain, including once in the group based on the ID. I try it use sop solver. but point count changes does not work. Is there any way what? Many thanks, Hyungi Jeon.