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Found 10 results

  1. Well, I went out into the RBD Constraint Forest Unprepared, and now I am lost in the woods. Any help would be appreciated. I'm trying to do something that should be fairly simple, and most likely is, but I don't have the combination to the Houdini lock to get the setup to work. In the example file I have an rbd box that has 10 faces per side that have been made into unique faces. They have glue constraints holding them together and are a rbdPacked object in my dopnet. There is a low rez smoke sim that pushes this rbd box into a collision sphere that is above it, and when the geometry collides with the sphere, some of the glue constraints start to break. All I wish to do is apply either a gravity force or a popForce to these rbd pieces that have lost their Glue constraint. I want the main chunk of the rbd box that still has a bunch of pieces glued together to keep on moving with no gravity or popforce. I might be trying to go about this the complete "wrong" way since I have very little experience with Glue constraints, But I see data in the geometry spreadsheet while in the dop net called ConstraintGeometry and this has a primitive group called "broken" which contains the glue constraints that have been broken due to collision. I would think I would want to try finding out which rbd piece that broken constraint belongs to and then use that to create an "applyGravity" group of rbd pieces so that I can do what I want to do. I just don't know how to do this in dops. Is this something that needs to be done in a sopSolver or geometry wrangle or....? I'm not to familiar with how to read data from the ConstraintGeometry and apply it to the Geometry data. When I middle click over my rbdsolver, it shows the main rbdpackedobj1 with Geometry and then CosntraintGeometry below it. They are like separate entities and I'm not sure the best way to get access to both in one node, if this is even the way to do it.? For example if I change a geometry wrangle to point to "ConstraintGeometry" instead of the default "Geometry", I can then read and manipulate data on the ConstraintGeometry, but then don't have access to the main rbd "Geometry" that I am use to normally working with. Like everything in Houdini, there are probably dozens of ways to go about this, I tried about 20 yesterday, without ever getting one to fully work. I ran out of search phrase ideas to try throwing at google after about the 6th hour of searching. Maybe using some of those copyData and applyData nodes would get the ConstraintGeometry data onto the Geometry stream so they can both be read in one wrangle or maybe that too is a completely wrong direction to take. I don't want to speculate any further since you could try things for a week and not get it to work if it just isn't the right approach. I love Houdini for its vastness and unbelievable tool set, but man, it can destroy you if you don't know how to do what you want to do, and can't articulate it well enough for a search string.! Thanks for any help. E rbd_constraints_v01.hip
  2. I have three individual components to this briefcase, the body, the handle rings and the handle, the body is a static objects and the other two are RBD packed objects, all concave. I am trying to get the handle to hang from the suitcase naturally but they are falling through each other, there is a slight reaction but i cant get them to completely react to each other. I have attached a zip of the three .obj files and the .hip file if anybody could have a look. Any help would be really appreciated ! Thanks! Assets.zip
  3. I have an animated cabinet that i have imported to Houdini from Maya as an FBX. I want to drop cutlery into one of the draws in the cabinet, i have imported the spoon .geo and made the cabinet a static object and the spoon an RBD object. when i drop the spoon onto some parts of the cabinet it lands fine. I want to drop it inside the draw before it opens but when i position it above the draw and play through it doesn't move, it is just frozen in the air. Im guessing its a problem with bounding boxes? Sorry im new to Houdini any help would be greatly appreciated! (Sorry for the bad angle, the draw is closed)
  4. Need help with simple VEX function

    Hello! New Houdini user here with barely 3 weeks in... so please bare with me I'm trying to write a small VEX function/expression to translate an object along it's Y axis by an exponential function... like gravity. The math behind is simple but I'm having trouble expressing it in VEX... I tried the following line with a VEX attribute wrangle node on a default sphere and it's giving me errors and the sphere just disappears on the 1st frame: t.y = t.y + (9.8 * ($T ^ 2)); If someone could steer me in the right direction I would appreciate it thank you :-)
  5. birth of a galaxy

    https://vimeo.com/188376689 Hi guys, I posted this on the SideFx forums but I also wanted to share it here... Basically, after the webinar on particles I felt inspired on creating my own galaxy system. The objective I put my self was to create a space opera style looking galaxy. But the real aim was to create the working forces behind it. Basically a system that can define the sun or suns, the initial speed of the traveling space objects and the gravitational pull forces affecting all of them. Also I added a particle absorb relationship, some big particles will gradually absorb the mass and size of the smaller ones, making themselfs more massive and bigger. I feel there are some quirks to polish but overall the core of the system is already there. Everything is based on real physics, or as close as I could get without making it super heavy. And indeed the results varies dramatically (in a good way) acording to the parameters input on to the forces, basically mass of the sun, of the debris around, distances, and initial speed. It was a fun excersice! maybe I will revisit it one day.
  6. HOUDINI - Alembic and RBD (Beginer)

    Hi! I'm starting with Houdini, and I would like to know how to combine a cached animation and Houdini's RBD. I know that this question has already been asked on this forum, but as I said, I am a beginer, and I would need reaaaaly basics answers. (I don't know any one who uses Houdini so sometimes I have simple problems that I can not solve). So my problem would be : - I receive an animation made with maya. I export an alembic (or a cache, FBX? Is there a best way?). I import it into Houdini. -The animation works, but when I set it as a RBD solver (or FEM, or anything that has something to do with gravity), the animation doesn't work any more. -I heard on this forum about a RBD keyframe node, about "Use geometry Transform", but I'm really too new to be able to use these informations. For exemple, if I want to use this alembic (attached file) : it is a little sword, I want it to be breakable, and to keep its animation. How would you do this? I hope somebody will find the time to answer to my questions, thank you! petite epee.abc
  7. Hi Guys, I'd like to know a way to control different forces, based on some attributes. I find is very easy to control Pop Forces based on position or velocity or Cd attributes... but I want to have this control using for example Gas Turbulence or Gas Surface Tension to control my fluid... Imagine I have one liquid that is flowing along a curve and after TX > 5 it will increase surface tension and turbulence. How would you do that?
  8. Animated Gravity Field

    Hi, I have a keyed gravity that affects a FLIP simulation (a box of water..), and I am trying to find how I can offset my gravity force to start with top particles down to bottom. Ideally I would have an animated box that would trigger the gravity effects on the particles... After a lot of research, it seems that I need to use the mask slot of the gravity but can't figure out more than that, as I don't see in the viewport any feedback for the scalar field and vector field. Help? Thank you!!!
  9. Hi guys, i'm trying to apply a force on the points of a geometry. So far i have a DOP network where i retrieve my geometry and its points, i give these points a mass and a velocity in my solver i'm coding. Then i add a gravity node. I read this article in the documentation : http://www.sidefx.com/docs/hdk13.0/_h_d_k__op_basics__sim_solver.html#HDK_OpBasics_SimSolver_ExternalForces that explains how to retrieve the forces in the DOP network but then how can i apply them to my points? Tell me if you need more informations. Thanks.
  10. gravity with rbd's

    Hey all, With my session I set up a simple grid fracture caused by a sphere. I was wondering how I can have the the grid stay static and still be fractured with the pieces fall. I've tried a glue network and making the grid a static obj. but my knowledge and the internets free resources are limited. I was wondering if one of you veterans could help me out? I've attached all the needed files. Final_Window.hipnc
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