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Found 120 results

  1. Pre-solve Post-solve

    what are exactly the pre-solve and post-solve input of popsolver ? there isn't any explanation about these input in the documentation?
  2. Hi all, i've got some points with trails and i'm filtering them randomly to leave some behind as the trails move forwards. each trail is split into a leading point and the trailing points, and each trail and its leader have a unique id. what I want to do is take the points i've left behind and remove them if they come into contact with another point trail that has a different id. so something like an attribute transfer but with a condition that checks the near points id and only transfers some attribute if that id is different. so the white points from trail 1 would exist until the come in contact with the red points from trail 2. Any ideas how to do this in vex or vops? Many thanks,
  3. I want to save the frame where the point joined to a group. I try this method: Its work perfectly, but my geometry have animation so i try to combine with this method: https://www.sidefx.com/forum/topic/21416/ But its just drop to zero my attribute after its get in the group.
  4. Hi ! I am making a project of a bridge destruction and i have a problem that i can not get solved I need to get my rbd to inherit a speed and initial rotation, when they enter the active state. I want to achieve something similar to this https://www.tokeru.com/cgwiki/index.php?title=File:Staggered_fracture.hipnc . but in the sop level and not in the dop. Best regards
  5. Hi guys, I have a rigid body sim with constraint network, I want to access the previous frame and current frame data of the constraints (impact, forces etc) inside a sop solver in DOPs. Currently when I call the attribute in a wrangle from the relationship geometry node I don't know if it's current frame data or previous frame. How to get both the current and previous frame data in a wrangle in sop solver in dops?
  6. Hello! How to Increase Particle Separation for Spray - Setup whitewater solver?
  7. Hey guys! Ive recently been trying to code a basic path finder, for pipes on a building. I have tried writing it in a vex for loop, without much success. Did i just code it wrong, or is this even possible without using the solver node? I have a lot of buildings and i want to generate the pipes without running the timeline, any ideas? Thank for the help!
  8. Hi, Iam doing a small vex RnD, i have some points with @active=0 and i make them @active=1 randomly by point number over time. lets say i have given them an attribute @temp =0, all i wanted to do is the value of @temp should increase from 0 to 1 gradually over frame when @active=1. for example, if the @active = 1 at frame number 30, the value of @temp of the same point should increase from 0 to 1 from frame 30. thanks in advance
  9. Hey guys! I'm trying to wrap my head around the solver sop. I have an alembic geometry that needs an attribute for the frame any point started changing position. What I tried was, inside a Solver SOP, appending a Point VOP where I subtract the rest position from the new one, compare the length of that delta and then write the frame on an attribute. The test and such works fine, but then my frame keeps changing, which I understand that it happens because I haven't figured a way to stop the value from changing. What I'm trying to achieve is to do a color ramp on the points by the attribute that tells which frame started moving. Any help will be very much appreciated! 20200316_CubeAnimation.rar
  10. Hello guys, Just a quick question. I'm studying new Sparse system for Pyro Solver in H18. First change I could see is that Pyro Solver sparse has 4 inputs rather than 5 and “Velocity Update” input is missing. Let's say I want to use a Gas Disturbance micro solver for sparse smoke. How I can connect it to the solver? “Shape” tab in the solver already has a Disturbance option. But, of course, the result is different if I use only the Micro Solver connected to the last input (Forces). So I guess, this approach is wrong. How I can achieve same result using only Micro Solvers? And, first of all.. Does new Sparse Solver allow to use micro solvers? Many thanks!
  11. Smooth Pyro Dissolve

    This is roughly what I'm trying to create, only with a smoother transition. In the example, the smoke is being generated by an animated gradient ramp, and the opacity of the text geometry is controlled with another ramp at render time. With Houdini, I want to utilize another workflow, I'm importing the whole text in my pyro sim as a fog vdb. But I don't want the whole text to be affected at once, I want to gradually dissolve the text from left to right, similar to the shown example. 1. (How) Can I drive the 'activeness' of the pyro solver with an attribute? 2. How can I make my density text vdb as opaque, as if it would be an sdf? Thank you in advance!
  12. Greetings, I have few microsolvers in my Flip Solver>Volume Velocity and I want to apply them to only 1 of my 2 emitters. Do I use a POP Wrangle after my MicroSolvers like (if viscosity > 500 then apply) or do i need to make some initial groups of my particles and apply the micro solvers to the favoured group ? To be more specific I use a GasMatchField and a GasStrainIntegrate with a GasStrainForce and I have 2 Volume Sources. If for example I go to my Popdrag in Groups I can see the option "stream_volumesource1" or "stream_volumesource2" but nothing like that in the microsolvers.
  13. pyro solver advect rbd piston

    hello. previously i saw a hip file in the forum about internal combustion of car engine pyro solver ignites and mooves the engine piston that in turn moves the gear of the car wheel. i searched for it but i cannot find it any help please thank you
  14. I want know how to control the constraint primitive node. I want make the collapse the house but this house easily breaks like a cookie even though adjust the constraint primitive. I have been tried a lot before, but haven't found a way. I would be very happy if you helped me.... house.hipnc RuralStall.obj
  15. Object Propulsion

    I'm trying to recreate the effect of small pieces of dry ice propelling themselves across the surface of water. First step was to figure out the propulsion. Thought I'd post my solution in case anyone was interested. The basic approach is to take a number of points on the surface of an object and use their normals as propulsion vectors to move and rotate the object in a (somewhat) physically accurate way. The points and normals can vary over time to create more random behaviour. This can probably be incorporated into dops somehow but haven't looked at that yet. It is also entirely likely that this is trivial to do in some other way and I've wasted my time. If so, please let me know. mt__propulsion__1_0.hdalc
  16. Smoke from scratch, add force

    Hey dudes, I'm trying to build a simple smoke solver from scratch to understand more how they work. I created a simple setup with density, temperature and buoyancy. Now I want to add a second velocity volume as a force to my simulation. But when I add the force, the velocity is increasing massively in a few frames. I have to mix my force with the existing velocity but I don't understand how to do this my_solver.hiplc
  17. hey guys i have a rigged character from 3ds max and exported it into fbx format.. and imported it into Houdini.. but the main issue is this.. the solver node is not working on animated mesh...its only reading a single frame :-( any suggestion.. i have attached file Hand_FInger.hip
  18. FLIP VORTEX SIMULATION

    Hi, I'm doing a project for a short film; and I am trying to create a water vortex. I looked into a few resources creating custom vector sources etc but I realised that I am having trouble using my custom vector source to drive a (basic) FLIP simulation. Do you have any alternative ideas that I could explore? Cheers.
  19. Hi everyone, I'm working on a little project of mine and I'm using wire solver with SBD spring constraint. I have attribute set up on the points(before the sim), but when I try to feed the strength parameter the expression with that attribute, it acts as if the attribute was zero. The vexpression I use goes like: @theattributementioned * 1000 I've created basic example file of what i mean. The attr “mult” is what I want the strength to be ( for example “@mult * 1000”.) Any input on this would be great Thanks, Hubert wires.hiplc
  20. DOP not keeping the dent done in SopSolver

    Hello, Alberto here! I've been following many tutorials and checking many examples in Houdini Help but after some days I'm getting a bit lost with this. I'm trying to do modifications to points in a geometry using an extra solver, during a Dop RBD simulation. I've tried to reproduce other working examples that I've found over the web but when I do it by myself, is not working. I want the extra solver to keep the denting based on impacts during the simulation. I read and saw examples about "Unpack - Do The Operations - Reassemble" inside the extra SopSolver and that's what I've tried to do in the attached file. I get the dent only in the frame of impact, not keeping at all any of the deformations during the rest of the simulation. I'm not asking for "fixing the file", I'm more into understand what I'm doing wrong and why. Anyway, Fix the file will help Thanks everybody in advance! Metaballdent_extrasolver.hipnc
  21. Hey guys iv'e been struggling to understand about Jacobian matrix and eigenvector why they are used in smoke solver how can they effect the look of simulation? Any ideas? Thanks
  22. The correct way to handle collisions?

    Hi there. I am currently building a cloth solver and have just got onto external collision handling. For internal collision I am using the same pbd approach they show off in the grains masterclass. I thought I would go about external collisions a similar way, using a gas collision detect I get the incidence vector and reflect it. Then add the resulting reflected vector to the position. if (i@hitnum) { vector incidence= v@hitpos-v@P; float mag=length(incidence); vector reflection= reflect(normalize(incidence), normalize(v@hitnml)); v@P+=reflection*mag; } The cloth still blows up, even at a high substep Annoyingly a simple if (i@hitnum) v@P=v@hitpos; seems to work worlds better albeit the colliding points get stuck in place (which is something I aimed to fix by setting the new position to the reflected vector). The reason I'm not using the gas integrator to handle this for me is because I was looking to learn how this system is implemented. What is the correct way to go about this? As always any help is greatly appreciated Thanks
  23. Hi all! Just a general question here. Having a solver inside a for-loop, looping through objects. I realize I need to turn off caching, or else it doesn't read in every new piece correctly. This seems to be extremely slow though, so I'm just wondering if there's a way to optimize this? What I'm doing is having an RBD sim, and having the pieces erode away. So I cached the sim, eroding the fracture elements in a for-loop and transfer the new pieces back to the simulation points. I hope and think this is a decent way to do it, except it'd be nice if I could cache out and iterate on the solver loop faster. Having 150 pieces, it's cooked 35 frames in 25 minutes now, and that's with a low-res VDB conversion, and naturally getting slower for each frame.
  24. Hi; In my very simple "RBD" simulation, the RBD solver simulates all of my packed geometries as a single object. How can I fix it? Thanks. RBDPacked.hip
  25. Seeking Solver Writing Advice

    Hello there I am just getting into solver writing. I am self taught and as such I have a fair few holes in my knowledge I aim to build a material point method solver for use in a mud flow effect such as this: https://www.youtube.com/watch?time_continue=42&v=jjeCDYvGJS8 To get to grips with a basic solvers I have built a mass, spring cloth solver: https://vimeo.com/343112353. However there are a few things I've come across that I can't find solutions to. Every timestep I am accumulating a force vector on each point and then I find the acceleration using a=f/m. I find the velocity v=v0+a*@TimeInc. And I find the displacement using r=r0+v*@TimeInc. This works quite nicely however I can't shake the feeling that the equations are completely wrong. Everywhere I look they mention using integration in order to find the displacement but it seems like a linear equation to me. Is this wrong and if so what should I be doing? I would also like to know what the gas integrator node does internally as I find it a bit of a black box. Many thanks George Coleclough
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