ParticleSkull Posted November 5, 2015 Share Posted November 5, 2015 Hello guys,I have this simple scene with a cloth (grid) pinned on all 4 corners and i'm trying to make it interact with an RBD Sphere. Can anyone give me a tip on how to achieve it? Right now the sphere is just passing through the cloth. Thx in advance.Alvaro Quote Link to comment Share on other sites More sharing options...
ParticleSkull Posted November 5, 2015 Author Share Posted November 5, 2015 (edited) In case anyone have the same doubt, I found this:http://www.sidefx.com/docs/houdini13.0/cloth/interaction_solversDepending on the wire order of the solvers on the merge node, you can make a one way interaction. In this case, if I wire the cloth first and then the rbd nothing happens. Altough if I have the rbd first, it reacts to the cloth but the cloth don't react to it. Also, I found this example so I presume it is possible - like everything on Houdini /Alvaro Edited November 5, 2015 by ParticleSkull Quote Link to comment Share on other sites More sharing options...
Farmfield Posted November 5, 2015 Share Posted November 5, 2015 Also, for some solvers you gotta set it up for correct two way interactions, like, say you want FLIP fluids to not only collide with but be able to knock over a RBD object, in the FLIP solver -> volume motion -> solver tab, you need to set the feedback scale to 1 - the default setting is 0 - else it will not calculate the particle collisions from the RBD side in the DOP. And this is of course to save calculation time when doing simulations, no need to calculate this type of interactions as, most of the time, these effects are either not something you want/need or you'll set it up in layers and sim one thing after another, for control. In the end, having this type of interactivity between the solvers is cool, but it's often very hard to control the end result and you'll end up in tweaking hell... 1 Quote Link to comment Share on other sites More sharing options...
ParticleSkull Posted November 6, 2015 Author Share Posted November 6, 2015 Thx again Johan.I've just done some tests trying to make some buoyancy of a sphere on a FLIP Tank with no success. As expected, by default, the particles react to the RBD object. Setting the feedback scale to 1 I can see some mutual interaction but it's not good at all, everything got incredibly unstable.Do you know I should do to achieve something like this? Quote Link to comment Share on other sites More sharing options...
dayvbrown Posted November 10, 2015 Share Posted November 10, 2015 Hey Alvaro, As far as the cloth feedback goes have you looked into the grain solver that was introduced in H14? Using it in sheet mode will allow you to get the interaction you're looking for. When you merge your RBD object just make sure you set the "merge" dop Affector Relationship to "mutual". The flips setup is definitely doable but it is a little fiddly (as you've discovered), the things to look out for are to make sure your scene scale is set appropriately, the mass of the object and density of the flip is set correctly, and that you're doing enough substeps (at least 2). Hope this helps! Cheers. 1 Quote Link to comment Share on other sites More sharing options...
ParticleSkull Posted November 11, 2015 Author Share Posted November 11, 2015 Hey Dave, thx! Just "faked" some cloth with the grain tools and it looks like it's working fine I've trie the buoyancy setup with no success. I've noticed that if I unable the "Use Volume Based Collision Detection" of the RBD object, it do interact with the water, almos start to buoy but then everything get horribly unstable. Also, more integration steps gives more instability. Whatever, it's too advanced for me. Hopefully in the future i'll understand it better. Thx anyway /Alvaro Quote Link to comment Share on other sites More sharing options...
Atom Posted November 19, 2015 Share Posted November 19, 2015 Have you turned up the subdivisions on the collision TAB? Visualize your collision geometry and see if it is high enough resolution. Some info here as well: https://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=41059&highlight= 1 Quote Link to comment Share on other sites More sharing options...
ParticleSkull Posted November 19, 2015 Author Share Posted November 19, 2015 (edited) Thx Atom. Great tips! Now it's working just fine.Here's some important points If someone else is having the same problem:- Like Johnny Farmfield said, something really important is to increase the feedback scale (FLIP solver -> volume motion -> solver tab). Sometimes 1 is too high. In my scene 0.1 worked just fine.- Decrease the object's mass and increase the FLIP resolution.- "Use Volume Based Collision Detection" must be on (it's on by default). If it doesn't work properly just increase the Uniform Divisions field, switch on "Collisions Guide" to see it's collsion mesh. Everything is under RBD Object node > Collsions > RBD Solver > Volume.Best,Alvaro Edited November 19, 2015 by ParticleSkull Quote Link to comment Share on other sites More sharing options...
localstarlight Posted September 24, 2016 Share Posted September 24, 2016 I'm also trying to get a basic RBD + Cloth simulation going on, and can't figure out how to get it working. Attached is a basic hip file, if someone could take a look. The RBD object is interacting with the cloth, but very strangely - it's colliding with it as if it's a hard surface, rather than deforming the cloth, and just continuously bouncing off it. If I change the order of inputs on the merge node, the ball just goes straight through the cloth without interacting. How can I get an accurate mutual interaction between cloth and RBD? Thanks! Cloth_RBD_Test.hipnc Quote Link to comment Share on other sites More sharing options...
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