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Found 17 results

  1. 2D dynamics

    What's the best way to simulate dynamics with just 2D shapes? Is it possible to use any of the existing solvers to simulate rigid bodies, but also flexible curve/polygonal shapes that respect line to line collisions ? I've tried using the wire and the grain solver (with rest length on a network of lines that connect the points), but the collisions only happen on the point level, resulting in penetrations between shapes. Is there anything else I should look into, or a working example I can take a look? thanks a lot georgios
  2. Grain particles explosion

    Hello I have a very strange situation where the grain particles suddenly explode along a line!.instead of volume collision I used "use surface collision" for collision detection for the body of the butterfly .as you can see there is no problem, but right the next frame the particles explode in such a strange way that I couldn't figure out why. I checked the setting for dozens of times... I found nothing wrong.I have other simulation with the same setting, It is worse.please let me know If something's wrong. thank you in advance
  3. Hey, Super new to Houdini here. Trying to stray away from my comp education and go into FX instead. We just finished a group project and it's time for summer break so I want to go back and do FX for a couple of finished projects of other groups to get finished comped shots to build a FX reel. For this particular project I wanted to make a grain simulation for a group that had a hermit crab switching his shell on the ocean floor. The finished project contained just a mesh with a sand texture on it together with stock footage for some dust and smoke when the crab flips the new shell from the sand bottom. I have attached my super quick way of re-doing it by following mainly a tutorial about the grainsource/grainsolver adjusted to this scene. My further a long hip is not that much better off anyway and much messier with much trial and error. Main problems are; -The particles keep moving for such a long duration even though I have friction parameters set to 1. Maybe the sim just have to run much longer? -Size of particles to represent sand obviously has to be quite tiny so I'm a bit unsure if I will have to scale them down all that much and create a super thick layer that covers all the way down to the tip of the shells flip animation (at ~54F) that to me looks like I'll be in the millions. -Camera seems off. I was reading up about camera exporting from Maya and asked a former student at my school that has been at an internship working with Houdini that said Null scaled to .001 is fine but it doesn't match the final shot. I will also have to double check this with the group that provided me with the assets. Still nice to get clarification. -Underwater gravity for the stones. I assume transfering Cd to the particles getting hit by the shell and then add a POP Force group that lowers the gravity specifically for those particles? -Maybe not such a big issue but particles clipping on the ground plane. -I also don't seem to be able to give the grains a shader/material like in the tutorial I watched. I have no idea what I'm doing wrong here. Just adding a dirt slaps it in /mat and gives it to everything except my particles. Although that works when doing the dop import afterwards when everything else is removed anyway. I have attached the hip file a long with the assets I have received from the group. cstSand.zip
  4. Constraint Grains to Animation (targetP ?)

    Hey guys, how can I use this target pins option? I have an animation in sops and I need the grains to be constranited to that animation. I guess the targetP attribute shouldn't come from Sops but I can't find a way to make it in Dops beased on that Sop animation. Any tips? Thx
  5. Voronoi to grain soft body

    Hello I am trying to make a voronoi fractured object into grain soft body. I split the object with voronoi fracure, and use for loop to create grains for each piece. On the dop level all looks great - all voronoi pieces are separate and bounce around the way I wished. The problem is when simulated mesh is read back and fed into point deform sop. The original mesh is not acting as separate objects. Is there an easy to correct this? Also, is there a way to create a glue constrain for grain sims? voronoi soft body.hiplc
  6. Granular Sheet - Pin Constraint

    Hey guys, I'm testing some cloth simulation using PBD but couldn't find a way to constraint some areas of it. I don't want to constraint it to another object, just want to make those particles to be "frozen". Can someone give me some ideas about this? Thank you /Alvaro
  7. Damping Grain Simulations

    Hey! I have a question about slowing down the motion of pop grains. Trying to find a setting or node that will cause the grains to lose velocity quickly, because they don't get to their rest state fast enough. In maya, I would use damp or conserve. Conserve changes how much force a particle can retain each frame. Turning the conserve down would cause the particle to lose much of the velocity from the previous frame. How can I do this with POP grains in houdini? Thanks in advance.
  8. So I've been trying to get the grain solver to use animated geometry as an emitter but I can't get it to work. I'm trying to create a sandman effect like this http://forums.odforce.net/topic/11658-flip-fluid-sand-girl/?page=1 but I cant get it to work since the project is quite outdated. The problem is that the creation frame occurs on frame 1, and If I change it, to say 1-10, it wont give me the effect I'm looking for, I moved from 3dsmax to houdini 1 month ago so be simple in your questions if you can
  9. more sand/grain question

    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
  10. Emit Granular Sheets

    Hi, I try to recreate more or less the same as sidefx presented in the demo video for grains. There a lot of bacon slices popp up and fall down. Unfortunately I have no idea how I can emit these slices with grains. Would be great if anyone can give me a hint where to start.
  11. Hi everyone, I am trying to use a grain simulation to create a sticky gum effect. (like this video) but I have a problem with the meshing. To create a skin out of my grain I first convert my grain to vdb (with vdb from particlesfluid) and then I use convertvdb with the polygon polygon option to convert this to a polygon “skin”. Everything looks perfect in the viewport but when I try to render, it is inflated at rendertime, ie: it’s not a perfect match with what I see in the viewport. If instead of grains, I use a sphere that I convert to vdb volume and then back to poly with the same convertvdb node with the polygon option I don’t get this volume increase at rendertime. See yourself: Is this a bug? Do you know any workaround I could get mantra to render the same result as I see in the viewport when using grain as a source? I saw this thread where someone talk about creating properties in a shader to get to render vdb isosurface directly without converting to poly: https://www.sidefx.com/forum/topic/29678/ But I still have to investigate that one, looks a bit complicated. As another workaround I could render my sim correctly by writing the vdb to disk and loading it in max to render with vray and it rendered correctly. But still I would like to know why mantra can't do it. thanks
  12. Sand collision

    Hello everyone ! I'm trying to get an object impact sand. To achieve this kind of effect I planned to create a setup based on this great idea: https://vimeo.com/155198661 Here is what I have so far: Unfortunately I lack the maths to go further. What I need is to spread my velocity vectors outward from the collision mesh and also to remove any vectors that are "BEHIND" the motion. I was wondering if there was a way to ramp down the density using a volume VOP and the BB attribute but no luck so far, or find a way to emit more grain at the front, avoid a constant emission within the volume. Do you guys have any suggestions ? Cheers ! sand.avi collide_setup_01.hipnc
  13. Hello, I would like to know if that approach is possible using PDB and the new grain solver: 1. Create a Granular solid from a VDB animated mesh and make all the grains move acording to its deformation and position. 2. Break some of the constrains so that some particles will no longer follow the VDB mesh. Thank you!
  14. Hello, I posted this a few days ago on the primary Houdini forum, but haven't gotten much traction with it, as it's a pretty strange bug. In short: I've animated the movement of a box, with grain pouring out of the box. Unfortunately, the grain doesn't leave the box cleanly: as it pours out, it creates a stair-step pattern on the bottom edge - one stairstep per frame - as if the box collision geometry isn't interpolating correctly during the subframe timeslot. Some notes: - Collision geometry is a single piece of geo that is translated inside Houdini via keyframes rather than an Alembic Cache or geometry sequence. - I added a time-blend node as recommended by jeff in the Houdini forum. - The "Re-evaluate SOPs to Interpolate Geometry" box in my static object node in my DOP network is checked. - Increased simulation substeps to 30 (The grain-stepping effect seems to generate one step per frame, so increasing the simulation substeps doesn't appear to have any effect. ) Despite all of that, the stair-stepping still occurs. Any thoughts would be appreciated! Thanks, Luke GrainStepping_02i.zip
  15. Hi all, new Indie user here, so be gentle! im trying to do a grain sim, and i have a complex animated collision object. i decided to cache out the collision volume to speed up sim times, as it spend a large proportion of the time "calculating SDF" i followed instructions i found online, and in the static object DOP i set the file mode to "write" and specified the filename as "collision.$f04.simdata" i then set the grain radius very high for a fast result, and ran through the sim. it saved out a series of .simdata files (22 meg each approx.) i then set the file mode to "read" so far so good. however, when i sim again, it -still- spends a similar amount of time "calculating SDF" and doesnt seem any faster.. what did i miss? many thanks for any advice, Robin.
  16. CG Workshop - Intro To Houdini 14

    Hey Everyone, CG Workshop is currently enrolling for the Intro To Houdini 14 course. I will cover a variety of material and get into many technical low level concepts, such as the math, geometry, and trigonometry involved in gaining complete control over an effect. When it comes to making great FX, there aren't any push-­button solutions. This course helps to lay that groundwork to understand what is going on under the 'hood'. I will take you step-­by-­step through the construction using production techniques in Houdini, right from looking at the UI and procedural modeling in Week 1, and eventually on to particles, grains and fluids. We will cover methods that give complete control when you're procedurally fracturing geometry, creating dust and debris, dissolving effects, as well as procedural animation and modeling, to name a few. http://training.cgsociety.org/course/introduction-to-fx-using-houdini Check it out and let me know if you have any questions! Spencer
  17. Hi guys, this is my first post here in OdForce, and let me just begin by saying that it's an awsome community! I'm trying to do a soft body simulation of raspberries falling and hitting a surface, thought I'd give a shot to the new Solid Grain object, mainly for it's speed. Right now I have one raspberry falling and my problem now is to duplicate the object so it look it's raining fruit! I've already done this with RBD, FLIP object etc with success, but I can't seem to make it work with PBD. Anyone has any pointers on this? Thank you so much in advance! PS: attached a basic scene file with a sphere instead of the raspberry! fuit_rasp_pbd_example.hip
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