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Found 121 results

  1. Orient / Lookat for Bullet Objects?

    Hi, I'm hoping someone can help me as I've spent too long on trying to work this out by myself now. I'm doing a simulation with balloons and want to have them start in randomised orientation and then slowly resolve their orientation to have the wider bit at the top. This seems to be possible with POP spin for particles, but I can't work out how to do it with bullet. So far, I've tried altering the orientation manually in a wrangle in dops and trying to find a way of getting a vector into dops, such as with normals, to then be able to compare to an up vector and add in angular velocity until they match. Altering the orient attribute in DOPs seemed to do nothing if you target it directly, so perhaps it needs to be worked on the intrinsics?? Nothing I tried seemed to work, so I'd love to know if there's a way of achieving this, so would be grateful for any help. Many thanks! Toby
  2. fit mass for bullet

    Hey! I have a bunch of pieces from a fractured geo, and I plug them into a rbd bullet sim. I have very big and very small pieces, which is fine, but the problem is that if I let the rbd packed object to calculate the mass obviously I get very different mass result (and that is absolutely correct), but you know, sometimes we don't want exactly the real thing so is there any way of fit the mass so after is calculated I can fit it to more suitable values? I was trying to find a way of setting the mass in the fractured pieces and turn off the calculation in the rbd packed object, but I'm not sure if there's a way of calculating the mass at sop level... thanks!
  3. Hey everyone. I was curious if there was a way to break constraints with an agent layer once they convert to ragdoll. For example, a crowd agent holding a sword, once hit becomes an active ragdoll. The sword is bound to the agent via an agent layer node. In DOPs, I'm trying to access the sword layer to tell it if state=ragdoll, sword's active=1, so that he lets go of his sword and it interacts with the rest of the sim as it falls and takes on any velocity from its original movement. Currently I can't find any attribute for the prop layer once the agent is packed and ready for dops. The only way I can access it is by name once it's unpacked, but this gets super slow and won't work properly in DOPs. Anyone know if what I'm trying to do is even possible? Or if there's a better way to do it? Thanks!
  4. Hi, I'm looking for a way of inheriting color on collision while using bullet and packed primitives. Let's say I have an object colored white - and I would like every single object that it touched to be colored white as well. Prefereabli those new "infected" object would infect others on collision. I did some search, found some topics on POPs using "hit count" - but nothing regarding bullet. Could you just point me in the right direction? Some use of collision data? Regards
  5. Hi! I need make fracture at sim time based on impact data (without prefracture). The point of impact is not known in advance, and I can't make a prefracture. I can do this during the simulation?
  6. Bullet boolean fracture with deforming geometry

    Hi Guys, I've been trying to create an rdb sim with boolean pieces where a dancing figure shatters and falls apart onto the floor. When pieces are activated I set deforming to zero. However, the pieces keep exploding off. I've made the shattered figure deforming with a "Deform Points" sop. This already seems to reshape the figure in a way that creates some artefacts. Perhaps this creates the intersecting geometry? I'm not sure. This doesn't seem to happen when I shatter with Voronoi. I'm not a fan of those pieces however. If it wasn't a deforming figure I'd probably next try to create some proxies with spheres and transform afterwards, but I don't see how I'd do that here.I tried to simply cut down the collision padding and shrink the pieces a bit, but still they explode. Could anyone give a piece of advice to make this work? Thank you! (Figure and animation have been supplied by the amazing Johnny Farmfield) fallapart_1.hipnc breakDancer_mocap_v03.abc
  7. Hey everyone, I'm happy to introduce Bullet Breaker Core, a toolkit for easy animation of bullet simulations. Link to Bullet Breaker toolkit -> gum.co/hTnq The purpose of Bullet Breaker is to allow for easy animation control of fracturing objects inside of Bullet simulations in Houdini. Bullet Breaker Core comes with digital assets to allow for ease of use in setting up and visualizing Bullet Breaker attributes. Bullet Breaker Core also comes with a brief tutorial which goes over how to setup bullet breaker compatible fracture geometries. Bullet Breaker Core does not use Houdini constraints and while it is possible to use Bullet Breaker with Houdini Constraints it is not meant to be used with Houdini constraints. Includes the demo scene file and all digital assets! Hope people find this toolkit useful! You can reach me at trzankofx@gmail.com for questions or comments.
  8. destroying animated geo

    hello, i am currently doing some r&d for a bigger project in which i have to destroy certain parts of a transforming building. so i started to animate a building-like shape with a growing collider inside, so I could start researching how to fracture and constraint animated geo and destroy just the parts that really get hit by a collider while the rest follows the animation. it worked out quite good, but now i got to the problem that even if the destroyed pieces are laying on the ground, they still sort of follow the overall animation. I tried to put deforming to 0 in a sop solver inside dops after reaching a certain speed but that didnt really help at all.. can some of you give me any advise? thanks in advance! animFracTest.hip
  9. Hi, all...need to do a shatter effect where the outer 'shell' of a static (for now) character/figure crumbles to reveal a different material/surface beneath. Been doing a lot of testing with a simple torus as it's a fair representation of the tubular topography of most of the figure (arms, legs, torso, etc). I feel I've finally got a good grasp on all the fracturing basics, but for the life of me I can't keep the outer shell fragments from interpenetrating with the underlying shell. I've tried: Increasing the DOP network substeps Increasing the rigid body solver substeps Switching the RBD packed object geo representation from Convex to Concave Altering the collision padding based on what it does to the guide geometry Increasing the number of fragments in connection with all of the above The changes either lead to little difference or in cases where I kick up the substeps and subsequently (I think) the precision, the fragments do the old-style 'exploding off the surface' thing. At this point, I have to wonder...in this situation should I just switch to the RBD solver? I'm okay getting hammered on sim time if I know it's going to work in the end. Oh, and a question about the collision padding...is that designed to pad the fragment intersection with other surfaces, each other, or both? Any help would be great. Really been banging my head against the wall on this one. -- moltenCrazy Shatter Tests - Torus - 02.hiplc
  10. In an RBD simulation I want to use both glue constraints as well as the i@active attribute to time my destruction, but seems like the two can't work together. Has anyone come across that before and has a solution? I have an example file that illustrates the problem. thanks georgios rbdContraintsActive.hip
  11. Hello, I'm starting to learn Houdini and following a course from PluralSight named Architectural Destruction, the final result is pretty much the same I need in my project, an exploding building with many different layers and materials. All the previous steps worked like a charm, however when I try to break one part of the building using a force I created, it behaves different from the tutorial, even configuring the constraints. Instead of exploding the area, like in the tutorial, it looks to blow the entire building at once, indepedent of the size or magnitude of the force, as the example below: Generating the force I have an attribVOP configured this way: And inside the DOPnet I have a geometryVOP this way: I tried to change the constants to reach the result, but with no success at all, is there any way to create some kind of falloff or decay for the force? How can I proceed? Any hints or ideas of what is going on? Thank you very much! Any kind of help is very appreciated !
  12. Hi all, I'm trying to create some physically accurate bullet sims using real world values for mass/density and friction, so I've been looking at some engineering tables for friction coefficients: http://roymech.co.uk/Useful_Tables/Tribology/co_of_frict.htm What I'm confused about is this: It seems that real world friction is calculated based on the coefficient of friction between two objects, eg wood & wood has a friction coeff of 0.25 - 0.5; wood and concrete 0.62; wood and metal 0.2 - 0.6. So friction is not a material specific attribute, so if I have 3 houdini objects, one wood, one concrete and one metal, how do I create realistic friction settings for each combination when I can only set a single friction value per object? Is it even possible? Also, how does Houdini calculate friction coefficient between two objects? Does it multiply the friction values? Or average them? Any help is much appreciated Thanks in advance!
  13. Hi all! I'm doing a rope sim with wire solver. And I wanna interact wire with RBD sim. I did each sim at the same time in the same DOP network. But it was not doing well. problems are... 1.Why the wire goes through the cube? 2.Why the cube breaks before the wire hits? Any solutions? Thanks. WireBullet_test.hip
  14. glue constraint issue

    hey !! why i'm getting this weird glue constraint issue the obj gets hit the glue broken then it gets attached again . thanks
  15. Hi, I have a case where I have, lets say an object which comes from bulelt sim, with v and w. Based on that object, I want to drive another bullet sim, updating v and w, so the rest would be calculated by bulllet sim. In the scene I attached it works pretty much, except it flips at some point. I understand that there should be some catches on quaternions. I suppose, there should be some sort of angle check and etc, but can't make it work... update_angularv.hip
  16. Duplo Bear via Bullet Constraints

    Here is a breakdown of how I made this bear made out of duplo blocks: The video isn't super comprehensive, I mainly cover setting up the constraints in SOPs, though I briefly touch on some other parts too. But the hip file is available to pick apart! Thanks! duplo_bear.zip
  17. Hi, I'm trying to achieve a particular effect which I though would be relatively simple (see attached image.) I have a shot I'm working on where I have a mechanical heart and I want a bullet to go straight through it without losing impact, shattering the heart as it goes. I have pre-fractured the heart geometry with voronoi and used glue to anchor it in place. I then did a simple RBD sim as you normally would when fracturing objects. However, when I used a sphere as a placeholder bullet with initial velocity, it just bounces off the heart. Even when I increase the mass of the 'bullet' it still bounces off. My question is, how would you approach this? I'm completely lost. Cheers!
  18. Bullet and Flips collisions?

    Hi, Can someone please help me confirm is bullet is compatible or not with flip simulations? I set up a simple packed geo as a static object for a flip simulation. The geometry collision is properly calculated as convex hulls… (image1) But as soon as I run the sim this weird shape appears (image2) It is like if the flip sim automatically converts the collision geo into a weird resampled volume. is this true? Would this mean that the flip solver will automatically convert the packed geo into a volume? Feel free to look at my set up… I simplified the scene to run a test. (the hip file is attached at the bottom) bulletandFlip.hiplc I also added this post in SideFx forums as is driving me crazy trying to figure the solution... I have figured a work around transforming my collision geo into volumes and then just using regular static solver but I would like to have a clear answer about what is going on here...
  19. Hi, I want to emit alot of coins which will be pushed outwards the earlier borned coins Like a growing stack of coins. What is a good way to do this? Cause What bullet now is doing is leaving all the intersecting geometry Alone (no popping)
  20. Hi all! I'm currently trying to find a way that I can control when an attribute on packedrbdprims coming into DOP's gets written to from the "Overwrite Attribute from SOP" box and when it gets written to from the bullet sim I have set up. I have a set of packed primitives with rotation animation on them being fed into a bullet simulation, I'm also adding an "active" custom attribute which is being used by a SOP slover in DOP's with a vex wrangle inside it to activate them when the value equals one. What I also want to happen is have the orient attribute on each packedprim update from the existing vaules from SOP's right up until the point when the bullet solver takes over and begins writing to the orient value. I know that I can add orient to the "Overwrite Attribute from SOP" box but what I 'm hoping for is a way to disable this function for each object as they become active rigid bodies, essentially adding to the orient values that exist on that particular frame and continuing with the sims values. Instead of having the sim take the orient values that exist at the first frame or continually updating those values as the packedrigidbodys are influenced by the sim. I know its poor form but I'm afraid I dont have the project file on hand to upload, sorry guys :S hopefully I can upload it next week if anyone needs to see it. Any help would be massively appricated! Many thanks
  21. Cloth/FEM and RBD/Bullet interaction

    Hi I've been searching the forum on this topic but didn't find much. Is there a way to get a somewhat correct collision behavior between the cloth solver and the RBD solver running parallel in the same DOP network? I've a bunch of cardboard boxes that's suppose to stack on each other. I'd an idea that the cloth boxes that had come to rest would switch over to be a RBD objects instead, to optimize the sim. But first I got to get the solvers to interact. Any ideas? A simple test scene with the setup is attached (without the switching stuff). Thanks / John Edit: Ops double post :/
  22. Hi all, I am trying some simple tests in dops using the bullet solver. I have hit a few stumbling blocks and would appreciate any input from you friendly people What I'm trying to do: I am trying to get a scene showing a pillar being picked up by a crane (like the ones in fairgrounds where you can use it to grab soft toys), the base of the pillar stays where it is and the rest of it gets picked up by the crane. As the pillar is picked up, the lower part of whats left is crumbling away as the whole thing moves. The setup: Because this will eventually be put into a game engine, I have to keep the number of fractured pieces down, so I split the pillar (Top, Bottom), and then I split the Top even further to isolate the "destructible" area. I fracture this area and animate both objects to be moving with the crane (transform sop within the SOP level) I then bring these objects into a dop network as RBD packedobjects but I can't seem to bring in the animation that is attributed to them. I change the "Initial Object Type" to all the the available selections int he dropdown, including Create animated static objects" but this doesn't seem to do anything. I do know you can do this on an RBD fractured object using the Use Deforming Geometry checkbox, but I'd prefer to work with packed geometry to reduce simulation times. Ideally, I would want the destructible area to just be parented to the Top of the pillar and then I can make it crumble by breaking the constraints. But I can't seem to do that either. In 3DS Max, in PhysX, there is an option to tag objects as "Kinetic" and then choose which frame to make them "Dynamic". That's a very rigid way of working and I'm certain there is a much more flexible way to do it in Houdini but I am still a beginner, especially when it comes to rigid body simulations. So to summarise, the questions I am left with are: How can you bring in animation on an RBD packed object? What would be the best way to achieve what I am trying to do? Thanks
  23. Impact Data from Particular Object Id

    Hello guys, How can i use impact data when an object hits a particular object in my case a ground plane to break the constraints, For eg - i have certain glued objects falling on the ground , some of them are breaking in the air while they release due to impact generated while i want they should only break once they collide with the ground plane else their strength should remain -1. So how could i extract object id of ground and use that as an impact data.
  24. I'm looking to transform one shape of packed RBD's into another. I've looked at the forum and a few of the examples. Specially the lego car which is awesome but they all tend to transform the same set of Packed RBD's from a rest shape to complete form. I am looking to transform from one shape of object to another shape of object. this is a pure Position and Rotation transformation and I think I'm just not understanding the way rotate work to show this I've made a simple houdini file. Any Help to better understand this would be appreciated.
  25. I'm looking to transform one shape of packed RBD's into another. I've looked at the forum and a few of the examples. Specially the lego car which is awesome but they all tend to transform the same set of Packed RBD's from a rest shape to complete form. I am looking to transform from one shape of object to another shape of object. this is a pure Position and Rotation transformation and I think I'm just not understanding the way rotate work to show this I've made a simple houdini file. Any Help to better understand this would be appreciated.
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