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Found 113 results

  1. Proper scale for FLIP

    So this has been mentioned in a few other threads but need some guidelines. My understanding is that FLIP has issues (unstable, flickering, collision, etc) for "small" scale simulations. By that I assume means anything under roughly a metre in largest dimension. What are some suggested starting points for scaling up your simulation for FLIP if its say, roughly a foot or so in diameter. 3X? 10 X? And what about speed to compensate. If you increase the scale 3X do you also need to speed it up 3x as well? There is also Spatial Scale on Solver and was wondering as a first step if i should try reducing to say .1 before I do anything else?
  2. With fast moving collision geometry and FLIP, what are some things to try to stop fluid from passing thru your geometry? Things I've tried - increasing substeps (using 8 currently) - reducing particle separation (I'm at .01 currently) What else should I try?
  3. Hi. What is the best collision method of POP simulation for debris in large scale destruction simulations? I think that such scenes in RBD are optimized by convex collision and packed geometry, so its computational cost is few. However, with POPSolver, we need to use Volume or Surface Collision (I thought ConvexCollision would work a while ago ...), so the computational cost will be quite high depending on the size of the scene. Is there an optimal workflow for generating a Pop simulation with PackedRBD simulation and accurate collision? Or is this something that you have to pay a reasonable cost for collision like VolumeSimulation?
  4. I (beginner in FLIP Fluid) have a FLIP simulation that gets crazy when I add a collision (static object) I use the test geometry shaderball, used 2 spheres with mountain sop, boolean with front and back of the shaderball. The two deformed spheres are the source. The rest (boolean difference) of the shaderball is the collision. Flipbook Without collision https://streamable.com/qkh2p Flipbook With collision https://streamable.com/922a6 Ii feel it has something to do with possible intersection between particles and collision geo, so I reduced the size of the sphere to leave a gap with the collision geo but the flip sim is still going crazy. Any idea? Issue with FLIP simulation.hiplc
  5. Hi! I'm making a chocolate dipped strawberry (strawberry model from 4dm-works.com). There are 2 problems. 1) When the strawberry falls into the chocolate, the FLIP is using both bounding box of the VDB and the VDB for its collision, creating this box around. VDB resolution is at 0.007 and uniform division for collision is at 500. (which I thought are high enough?) so I'm not sure what's up. 2) The 2nd problem is that the chocolate doesn't stick to the strawberry. I have the friction, viscosity, density and stick on collision on, but nothing's been happening. I have a feeling it's something super minor somewhere.. but I can't seem to figure it out. How can I fix this? (Bound_Stick_Question.hipnc) Thank you in advance for taking a look at it! -Y
  6. Whitewater leaks through surface

    Hello everbody! Im struggling with the whitewater sim. There are some post about it but they didnt helped me. I tried everything they told but its not satisfaying. I created the sim from the Shelfttool and played with some settings. First, the whiterwater particles were floating outside the mesh or didnt even collide. I pushed them closer into the mesh with some settings. The fluidsolver works fine. Then i recognized that the particles are inside the mesh. They are skipping the first surface and they are floating inside and now i need help I have another testproject with same problem. I hope you guys can help. I am out of ideas Here is the scene Thank you glass_scene.hip Glass OBJ.obj
  7. Flip Fluids deforming collision objects

    So I am quite new to Houdini, I have a fairly simple setup where I am simulating the behavior of a viscous material where viscosity is increasing exponentially with age and multiplier. So by frame 120 particles stop moving. I am emitting in a line in a loop back and forth so slowly the particles start creating a layered wall. However I have encountered 3 very intriguing problems which for the world in me I cannot seam to figure out: 1 - When meshing the particle data the particles that are close get meshed (obviously) and I don't really see the layering that I need to. Tried creating a very highrez model but didn't really work. (Is there a way to use the viscosity or age variable to stop particles from meshing together and keep the layering intact?) Currently using VDB from Poligons then converting it. 2 - Despite a very high Viscosity, the particles move somewhat when new layer of particle is added on top. Is there anything like Pop-State (as in previous releases) where I can freeze the particles with attributes? currently using (if viscosity>100000 {v = 0,0,0) to set velocity to 0 once viscosity is high enough. 3 - If I wanted to use a deformable (cloth/plastic/elastic) object to fill the flip fluid into how can I go about this? I hope some of you brilliant houdini artists have some advice or tips on how to go about solving these problems. Houdini file attached. SimCon1.hip
  8. Hi Guys... How are you? I know there is a lot of information there that try to explain why this issue happens. However, I´ve tried to set up a basic scene to replicate the most common problem out there The scene attached is not the final or nothing at all... It was at the point of testing when I'm writing this post HOUDINI COLLISION FLIP ISSUES The main idea is this: Making the inside of the character-filled with liquid (just a little more than half). The liquid MUST be the same at all time. I had to invert signs of the static object to make it "work" And here the magic dust came along. THE LIQUID DISAPPEAR I´ve tried the following attempts with no luck so far: Reduce the grid size to 1 so the voxels of the flips have the same size of particle separation, Reduce the Particle scale to 1 to avoid conflicts in collision Try to multiply the scale by 3 to make it bigger and up the timescale of the solver to match it. I also try to advect the collision field with a volume source with VDB but it was worst and I discard that option in the minute Thoughts: I think it has to be with the particle collision mixture between volumes and particles. For some reason (i think particle accumulation) the solver reaps particles that are very close together and in the next frames, it does the same thing over and over until you are left with no particles at all... I tried to adjust the reseeding and even not reseeding at all and no luck either... It will be SO COOL to finally leave this point crystal clear to avoid future users to melt their brains out Cheers to all Peace! Wolf.rar
  9. Hi, I'm doing a vellum hair simulation on a character that starts partially under a ground geo. I also do other vellum sims (as foliage) that need collision with the ground. But my hair gets stuck under de ground geo. How can I make sure that only the other sims are colliding with the ground and not the hair? Thanks!
  10. Hey guys, I'm having some issues with a FLIP collision, seems my VDB collider boundaries are affecting the sim, anyone knows what can be causing this? I'm using static object + static solver with a proxy volume as collider. Thanks!
  11. Hi Guys, Very new to houdini so spare the studpidty, Ive set up multiple rocks in sops using the copy to points node. I wish to then perform a rigid body simulation on these rocks so that they collide with both the ground plane and each other. However, the effect im achieving is the group of rocks falling and interacting with the ground plane as a single large grouped entity. This is despite me setting the bullet collision data as concave and not concave. Thanks in advance all! Procedural Rocks.hip
  12. Hey everyone! If we have particles colliding with an object and bouncing off, we can transfer colour to the hit position. Once the particles have bounced off the object, the colour is also removed. How do we get the Cd to remain on the object once the particles have bounced off? Any idea would be great! thanks
  13. Hi, I am working on an airplane destruction with a skeleton underneath the fuselage. At first this worked quite well. ( SimV15_V5_goodImpact ) But after importing a newer version of the model with wings it completely ruins the simulation. ( SimV15_V7_Glitch ). Once I removed the breaks in the fuselage and skeleton mesh it works as it should again but the skeleton glitches through the fuselage. ( SimV15_V7_WingFixSkeletonBug2 ). So I know why this happens but I don't know how to fix it. I also don't really understand why the skeleton glitches through the fuselage mesh all of a sudden. Can two deformable surfaces work together properly? In attachments, you can find the file ( Simtest_15_V10WingFix_SkeletonIssue ) and the ABC ( B25_V30_Turbo_AllWingsV2 ) Btw I used steven knippings rigids 3 tutorial to get the metal deformation. Thanks in advance SimV15_V5_goodImpact.mp4 SimV15_V7_Glitch.mp4 SimV15_V7_WingFixSkeletonBug2.mp4 Simtest_15_V10WingFix_SkeletonIssue.hipnc B25_V30_Turbo_AllWingsV2.ABC
  14. Problems with two FLIP objects colliding

    So I'm in the middle of creating a waterfall scene which is going to flow down some geometry and collide with a lake. I've set up both the emitters for the waterfall and the wave tank for the lake in separate DOP networks. However when i try and bring the particles in from the waterfall into the lake DOP the particles don't seem to be having any interaction, the waterfall particles just fall though my static objects even though they should be colliding. Any help would be appreciated Thanks. Edit* I've noticed that the bounding box in the flip solver was not including the waterfall particles which fixes the problem of them not moving however the particles still do not interact with the wave tank. WaterFall_New.zip
  15. Animated colliding objects

    I have a project coming up that will require me to hand animate objects but get them to collide with one another. I'm an experienced Houdini user but setting up DOP simulations has never been my strength. I've attached a hip file with the basic situation here: moving_furniture.hip Furniture will be sliding around, probably animated by hand. The objects need to bump into one another and react naturally while doing their best to follow the target animation. I had assumed that this would be some sort of combination of RBD objects, proxy Geo & pin constraints, but I've been unable to understand how to wire it up. There are so many great examples using this sort of thing but nothing that really explains how to combine following constraints that are animated in world space. Thanks so much
  16. Hey guys I have a destruction simulation here and I want the smoke to collide with the debris, so i turned by pieces into vdb (as you can see in the first picture) and put it into fluid sim but it looks weird (as you can see in the second picture), half of the pieces are missing. This never happened in houdini 16.5 but from the 17 version i am having this issue, is there anything new that i am missing? I have also scaled the density to -1 because i am using vdb.
  17. Hi, I like to do this... Create wires (kind of stems) attach the geo to the last point of curves (bloom) and during wire DOP collide the curves (wires) also with the blooms... How to do this? Sees to me like kind of cycles for counting this..? What should be the data flow? Thanks. B.
  18. Stick RBD Objects On Collision/Impact

    Hi guys, Just wondering if anyone out there could give me a hand or point me in the right direction for something I am trying to achieve with an RBD simulation. Basically I have created a fracture simulation which gets launched at a character and I'd like to be able to stick the pieces into/on the character. I have been trying to investigate dynamically creating glue constraints but have hit a bit of a wall. I have seen that I can record impact data but I am not too sure how to process this in a way that would then lock the RBD object to the collision object. Any help would be super appreciated.
  19. Hi I've got some geometry and want to use it as collision geomtery. when I change this geomtry to volume using by vdbfrompolygons node, It looks like second pic. I think It's because of unfilled geomtry, but problem is All geomtries I've got are unfilled like this one. My purpose was make geometry to volume and use it as volume sample at staticobject node in dopnet. How can I fix it ? or If you know other efficient ways to make unfilled geometry as collision geometry, let me know please. Thanks for read, My English is poor sorry
  20. Hi, Does anyone know how to create variable friction for collision geometry when using particles In houdini. In maya or realflow you can create/paint friction maps. I was wondering what the houdini workflow is to create this. Thanks in advance, R.
  21. RBD on fast moving collider

    Hey guys, little question about RBDs interacting with fast moving colliders here. So Lets sayI got rocks rolling down a mountain and the mountain shape start to fold/move rapidly. In this case the rocks stop roling and get pressed to the collision geometry - due to the speed of that collider. Any ideas or quick setups on how to counteractthis and get the stones roling again?
  22. Granis collision help

    Started trying to make a Hour Glass effect but when i press play the grains appear on the outside of the geo, not sure what the problem is any ideas? HourglassSim.hipnc
  23. Hello, The title may be not that clear so rather then tell, I will show what I need to achieve first and then I will describe my approach (or better say approacheS, because I have been banging my head against the wall for quite some time with this). So basically here is what I need (did this quick and dirty animation in C4D): https://www.dropbox.com/home?preview=test.mp4 Now the tricky part is that this animation has to loop. Initially I started in C4D. Made some particles crawling along the surface of the statue, cloned some primitives on those particles and applied dynamics. It all works great but how do I loop it. Simulations are are very tricky to loop (especially in C4D) so I decided to go the Houdini way and try to build procedural setup that would give me similar result. My initial thoughts of the setup are the following: - scatter points on statue - make them move with the noise and use (minpos() function to stick them to the surface), and use periodic noise so the movement can be easily looped. - every frame attribute transfer normals of the statue to the moving points, so that when I copy objects they will be aligned to the surface - copy objects onto points and make sure there transformation axis is at the bottom so that when copied they appear on the surface of the statue - check for intersections with the statue (still not sure how to approach it but as far as I remember there is a way to see if two meshes intersect or not - if they intersect, move the object away from the statue along the normal of the point it is copied onto (I think this will have to be done in solver so that I move it slightly and then check for intersections again, because the distance the object has to be moved may differ) - I still do not know how to avoid intersection between all the objects on the statue themselves ( do not have any ideas so far) For now I am stuck on trying to loop the movement of the points. I can loop them easily in 3D space but when I minpos() them on to the surface they jump from time to time. I understand why this happens but can't figure out how to avoid it. I tried attrib transfering the normals of the statue to the points every frame (in solver) and then calculating the cross product between normal of the point and vector generated bu the noise. This gives pretty smooth movement but the loop breaks of course as you may have guessed. Anyway, thanks for reading this far. If you have any ideas on how to make it work, please let me know, I appreciate any input. I have posted same question on the SideFx Forums on friday but it is still been reviewed (takes so long). Maybe I am overthinking things and there is easier way to do it say in C4D, in case you know it, please let me know. And do you think my thinking process is somewhat right? Looking forward to any help. Have a great day everyone!
  24. Houdini Pyro Collision

    Hi there everyone. This must be a common question but I just cannot seem to get the Pyro Collisions to work correctly there is defiantly something I am missing and I would greatly appreciate some assistance. So this is the issue I am having. Below you can see the Multi Field going through the Collision Field where there are no holes. This is the Multi Field. Here is the Collision Field on its own so you can see its a solid Piece. This is the Temperature Field. This is another angle of the actual Geo at the same frame as the images Above. So I just wanted to mention what I have observed and what I have tried. first my observations, the Multi filed is only partly interacting with the collision field, in that some of the smoke travels along the ceiling of the roof before finding an exit and pushing outwards. Secondly have I have tried, Is using the Houdini shelf Deforming collision object but it only dose 2 frames then hits my 32gb memory cap and my system crashes and restarts. This is if the mode in the Static Object is set to Volume Sample. If I try Ray Intersection it dose not work, there are holes in the collision Field. so the method I am Trying to get right (Based on the Images above) is the secondary Volume Source set to collision. Here are my VDBs and I am merging in the Cached RBD Data. And this is my Volume Source for that VDB Surface If you need anything Please Let me know ! Have a Great day, Jody.
  25. Hey folks! I was hoping to gain some understanding on how I might 'mask' out areas from the advection process. I have a recursive growth setup and want to add some objects into the scene where the growth will react to and grow around it... Im not sure the best way to go about this so im not subtracting the colision surface from the growth vdb every frame... ideally some vops setup to multiply the negative space of the collision geo with the direction of growth (velocity) so that it zeros out as it nears the surface. Im using a modified version of this setup i found on the forum. attached youll see the surface i want a collision with. http://fx-td.com/content/misc/recursive_growth_v2.hiplc Many thanks!
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