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Found 128 results

  1. Bullet and scale

    Hi, I'm experiementing a bit with bullet and fracturing and did some simple tests. If I know it correctly then the simulation base unit in Houdini is meter, so 1 unit (e.g. a basic polybox) is 1 meter large. If I now try to simulate real geometry like a bottle or a cup of tea, then my geometry is maybe only 0.3 units large for a bottle. These are my results: First, the real size, 0.3 units large, no substeps, convex collision geo: bullet_01_convex.mov As we can see, the collisions are quite inaccurate and the simulation is jittering a lot. That's simply because the collsion geo is inaccurate. So I switched to concave and tried again. bullet_01.mov That's more accurate but still jittering a lot. So I switched back to convex and modified the collision padding to get a better representation. bullet_01_convex_collpad.mov Collision is better, but we still have a lot of movement in the geometry. So maybe it helps to increase substeps? I increased them to 10 on the dop node. bullet_01_convex_collpad_sub.mov As you can see that was not such a good idea, the parts are jumping around like crazy. So Now I started with an increased scaling of the geometry and increasing the gravity at the same time twice, once with convex once with concave. bullet_02_concave.mov bullet_02_convex.mov Now the convex sim starts to look better. Just for testing, I increased the scaling up to 3 and did it again: bullet_03_concave.mov bullet_03_convex.mov Looks very much better. Now I tried with my real geometry: bullet_04_concave.mov still some jittering, and not enough bounce, so I increased the bounce. bullet_04_convex_bounce.mov And a bit more bouncing. bullet_04_convex_bounceHi.mov Now it looks more the way I want it. So my final conclusion is: Even if it may be physically correct to simulate a 30 cm bottle in real size, the only way to make it work as expected is to scale it up several times, simulate and scale it back down. Is this correct and can anyone confirm this? Maybe I'm completly wrong and simply missed some of the many settings in Houdini so I attached my scene. Here the uniform scaling of "transform6" node in the "alembic" network is connected to gravity to make it automatically higher if the geometry grows and bounce of groudplane and geo is higher than default. Scene file: bottle.zip bullet_01_convex_hull.mov
  2. Hey guys. I'm trying to figure out a destruction setup for things like fences, wooden frames, plywood walls (that thin stuff thats really easy to put a hole in accidentally) etc. The part I'm stuck on at the moment is how to mimic things that are nailed together. Specifically, how to set it up so that when the fence/frame/whatever is hit by something, it doesn't just break apart, but instead just becomes a slight bit loosened, causing it to wobble a bit and fall over slightly. I realize that explanation probably makes little to no sense, so I've included two reference images. One depicts the effect that would happen for an entire fence, the other is for a single beam. I've got an example scene that uses the Cone Twist Constraint. It it gets me part way there, but is obviously way to static, and just stops suddenly. What I would like would be some subtle wobbling, as well as the beam the rotate down abit (to mimic the photo with the horse). I had the idea of using a Glue constraint with a bit of stretch. Problem is, I have no idea how to get a glue constraint to stretch (or if its even possible) and I couldn't find anything on Google about it either . Is anyone able to point me in the right direction for figuring this out? I'm still struggling to understand constraints so any guidance would be extremely helpful Nailed_Wood.hipnc
  3. fluid driving rbd/bullet?

    Hi, Im trying to let a fluid drive my rbd/bullet object but it just doesnt work. Never did this before. Does anyone have a quick example? tried multisolver, merge Left input to advect right, ... Just a simple smoke shelf and object would be enough as a example. Like particle advect, but with geometry. THNX alot
  4. Hello, I'm doing a simulation where a car drives through a brick wall. The scene will eventually be imported via alembic into C4D for texturing and rendering so here is where I'm getting stuck: I imported the car as an obj, cleaned it, converted it to polysoup, made a low res proxy (using the ray sop) for simulation, and then after I get the sim the way I want I export the point data of the sim and then use transform pieces and connect the high resolution car. However, I'm not sure how to export the car with selection tags for texturing individual parts of the geo in C4D. I'm using alembic to export from Houdini to C4D. It seems like once I convert the car to regular polygon mesh, all the individual pieces of the car fall apart in the sim. I would use an HDA and the C4D Houdini Engine but we are on R16 at work and will not have R17 available to us for this project. Is there a way to save out texture tags in the polygon soup so that when I save the alembic file they are baked in? Any ideas are welcome! sim_example_js_v01.hipnc
  5. glue network and deforming mesh

    Hello! I have a prefractured animated mesh and I'm using bullet solver. When I simulate as a static mesh everything goes fine but when I switch to "create deforming active objects" in the RBD packed object I get odd results and the glue network seems not to be working. I've realized that the glue network only is created once in the beginning of the simulation. Should it be updated every frame if the mesh deforms? Thanks in advance!
  6. Slow down fast moving parts

    Hello guys I am creating the brick wall destruction. Take a look what I have now. https://drive.google.com/open?id=0ByHRy_pSYAhgRDZLa1RXcjBZRlE On the screenshot I've checked the zone where are lots of fast moving pieces. This fast movement and rotation is not typical for the pieces of concrete and bricks. How can I make all the pieces act more like a concrete, and slow down their energy much faster to make them stop much faster? I used bullet solver. The density (mass) of pieces is about 3200. Bounce is set to 0.01, friction to 100. Thanks
  7. How to remove RBD jitter?

    I'm trying to recreate a shot I made in C4D: But I'm having difficulty with the beans. They drop onto my groundplane, but they don't settle down - way too much jitter in the center of the pile. With C4D dynamics, I'd adjust the linear damping & angular damping - but I can't seem to find the equivalent in Houdini. Or, I'd increase the simulation substeps (which should theoretically increase accuracy) - but every time I increase the substeps in Houdini - whether it be for the whole DOP sim or for the rigid body solver, the sim becomes increasingly more chaotic, with pieces flying in all directions. I've tried tweaking just about every param on the bullet solver, but nothing seems to be fixing it. Thoughts? Thanks! RBD_Settle.zip CoffeeJitter.mp4
  8. Bullet collision relationships

    Would some kind soul please be able to show me the correct way of using the collide relationship dop in order to create 2 collision objects that will collide with everything else in the sim (like a fractured wall or similar), but not with each other? I'm sure the answer lay here but I'm not having much luck setting it up. Have attached a basic hip. At the moment sphere2 collides into sphere1 as I'd expect, then both go on to hit the wall. What I'd like is for sphere2 to pass through sphere1, but both spheres will still hit the wall. Collision_relationship.hip
  9. Hey guys, My scene right now involves an octopus tentacle slamming down and destroying the middle of a ship. I shattered the ship and added angular velocity in SOPS to the shattered pieces, which is then brought into DOPS with the 'inherent velocity from point velocity' option. I then added an 'rbd key activate' to activate once the tentacle hits the ship. The problem is the whole center of the ship is exploding out at once from the inherited velocity. Is there a way to only activate the angular velocity apon collision with the tentacle as it moves through the ship?
  10. Hey, guys! I am currently working on my bachelor thesis film. A scene contains a crystal hitting the ground and shattering. Unfortunately, I experienced a strong flickering in my rendered images, different from the typical sampling noise. I am not sure what causes the flickering. I assume the Bullet sim itself is the reason. The pieces intersect a little bit and never stop moving completely. The problem is more evident with a glass-like shader than say in a clay shader. I played a little bit around with the Collision Padding and the Threshold parameters, but it didn't bring the cure. I also tried some symptom treatment via freezing the pieces, when they reach a certain velocity threshold. But this wasn't a true solution because the pieces sometimes stopped in the mid-air. Maybe the problem is shader-related... In earlier stages of my work I had some problems with the normals, but in the meanwhile I fixed them. So I don't think the problem is normals-related. Does anyone have ideas how to fix this? I included a video showing the problem and the scene file. Edit: Problem Solved! flickering_002.mov crystal_001_v196.hiplc
  11. RBD stylish collapse

    Hi guys I'm trying to simulate two tall buildings destruction like the attached image. So I fractured my entire blue building and the wing of the red building and I made a lot of constraints with different strength and break forces. The plan is to make it stylish that the blue building collapse as height of the green rectangle and the wings of the two buildings fracture apart and few pieces in entire buildings. But in all different situation that I tried, the blue building starts to rotate counterclockwise after colliding with the red wing. So do you guys know how should I approach this problem? Thank you in advance
  12. Hi, folks. I need to set up a simulation where dynamically-generated arrows fly, then collide with a deforming surface and stay stuck to that surface (shields carried by moving soldiers). Importantly, the arrows should NOT just align along the prim normal on collision; they should protrude at the angle at which they collided. This is a topic that's come up before, but I haven't been able to find a satisfactory answer about it. Some suggestions don't quite hit all the elements I need; some are for older versions of Houdini and so might not be as relevant/accurate (I'm on H14). The approaches I've considered are: 1. Particle-based arrows that stick. It's easy enough to copy arrow geo onto a particle sim, and have the particles stick to the collisions surface. However, then the particles have to start inheriting the orientation of the collision prim as it continues to move. This could be handled two ways: The collision geo is deforming. In this case I'll somehow have to calculate how the collision prim has transformed from the moment of impact to the current time. The collision geo is transforming. In this case I'd use rivets to attach non-deforming stand-in geo to the moving collision objects (which don't change shape). Not ideal, but it might make it easier to work with the orientation values? 2. Particle-based arrows that create geo. Having already grown sick of the mathematical jungle of quaternions, matrices, and dihedrals, I wondered if a better approach might be to make each particle spawn some geo in the colliding object's network instead (presumably using a SOP Solver?) , then die. This would hopefully eliminate the need to continuously update orientation. 3. RBD-based arrows with constraints. Moving away from particles altogether, I wondered about using simple Bullet geo for the arrows, and dynamically creating constraints to pin them to the shields when they impact. An advantage of this method would be that it would allow realistic stick-like collisions and bounces for loose arrows--something particles can't really do. If anyone has any thoughts about which of these methods is most promising, or has any specific advice about how to implement them, I'd be extremely grateful to hear. Thanks in advance!
  13. Bullet collision ignore

    the "collisionignore" point attribute works when it is ignoring static RBDs, however it doesn't seem to work when ignoring active RBDs.. is this a bug?
  14. Hi everyone, PROBLEM: no interraction between flip and Fracture object WHAT I DID: i create a flip tank, 1 cube shattered falling apart into the flip tank, and another cube falling straight into the tank. The problem is, when i make a cube fall as it is, the interaction are great, but from this cube are shattered and turn into dynamic piece, they are no more interaction. Anyone have any ideas ? I used houdini 13 (because of a lack of ressources) I linked the scene files, if u want to have a look. Thanks a bunch test.hip
  15. min_activation_impulse problem

    Hello all, I'm using Houdini 15 and the new point feature of min_activation_impulse together with active and activationignore. It's a simple bricks wall and a cone smashing bricks. The problem is Whatever value I put for min_activation_impulse, as in the scene is 500, the bricks react always. What am I missing? Thank you bricksWall4odforce.hipnc
  16. Hi! I was wondering why when having active RBD objects in a passive RBD container start to gain very aggregated velocities when the passive deforming RBD starts moving around. I was expecting to have pretty much a box with some objects in and the box moves around. But when the box moves around all RBD contents inside would just go crazy and pop out like popcorn. Tried multiple collision substep settings, played around with density ratios, bounciness, all kinda the same result. I'm using bullet rbd solver for that. Thanks! Nhat
  17. Recently I discover something interesting after smash my head against wall for a few days. Im creating a simulation using bullet and packed prims, and I need activate (using i@active variable ) the pieces in choreographed way over the frames But the thing make me crazy is that bullet change ptnum of each packed primitive over the time, and I think is about some priority list inside the algorithm of the solver. because after the simulation I need to atach some atributes for each simulated piece. Then I realize that I need to attach theses attributes before simulation or atach some sort of ptnum tracking for them. bullet activate order points_v001.hip
  18. Hi all, I have been learning to use bullet sim for the past few weeks and was trying to add thickness for my breaking teapot. I have unchecked "Create Inside Surface" at the Voronoi fracture node to remove the insides, but currently the surfaces are paper thin. I have tried all the extrude nodes, but my surface points seem to get wonky. I am also wondering if there is an effective way to auto freeze the small pieces from rolling around, I have tried some solutions from the forum but it haven't completely stopped it. I am guessing it is a drawback for using bullet sim or I shouldn't be cracking the geometry into really small pieces. I have attached a picture and file too Thank you! voronoi_v002.hipnc
  19. Shattering car windscreen effect

    Hi All! Relatively new Houdini user hear already stretching my very finite knowledge to breaking point! I'm attempting to create a shattering car windscreen effect whereby the glass bends and contorts overall but at the same time breaks apart into smaller shards. I have my deforming windscreen geometry that I've brought in as an Alembic import (The animated geo's from a Maya Ncloth sim). I also have a static version of my windscreen geometry that I've shattered into glass fragments. I was hoping there might be a way to set up a constraint network whereby the glass fragments stick to the deforming Alembic geometry (Which I've turned into a Static RBD) while at the same time allowing me to pick and chose when the glass fragments fall away from the deforming object. I'm able to glue all the glass fragments together but having these follow along with the deforming imported geometry is a little beyond me at the moment Any suggestions for the set-up would be massively Appreciated!! J.
  20. BulletSOP - Open source

    BulletSOP is implementation of Bullet library (bulletphysics.org) inside SideFx Houdini (sidefx.com). It's a plugin for creating incredibly large rigid body simulations on average PC. The Tool is very powerful, flexible and speed is very impressive as well as memory footprint. The plugin is free and without limits! So you can create truly stunning massive simulations. BulletSOP is compiled for Houdini production builds. It includes many example scenes (beginner -> professional) which are probably the best learning resources. Official repository on Github. Main features: - Bullet RBD Solver - Support for multiple Broadphases, Constraints Solvers - Loading data from previous frame - Geometry decomposition (Tetrahedra, Voxels) - Static/Animation body - Convex Hull - Compound Hull - Deform static Hull - Primitive Hulls - Constraints (auto-generating, spring, 6DoF) - Collisions Groups - Object Forces - Point Radius Forces - Delete Duplicity data - Instancing - Emitting system - Includes many example scenes for studying - Support for Windows(64bit), Linux(64bit) and OSX(64bit) Links: Houdini: www.sidefx.com LinkedIn: www.linkedin....Houdini-4796605 More author's videos: vimeo.com/user3251535 Create freely, simulate quickly and enjoy fully! Best wishes, Milan Suk
  21. The Hero vs the Villain! Personal project. Wanted to do some massive house destruction, also had an idea about these two characters. Maybe you can recognize one of them xD Modeling: Maya. Destruction dynamics: Houdini. Rendering: Houdini, Mantra. Compositing: Nuke. More info in the video description
  22. Hey everyone! I am in the RnD Process of having a bottle filled with water crash to the floor. I have set up the Bottle with Bullet and constraints. Which works fine. Also the FLIP Fluid without Bullet works fine too obviously. Now if I merge the whole stuff the first few frames mostly work well. But the moment the bottle crashes to the floor the Bullet Sim kinda gets horribly explosive. I tried different flip collision method, yet they do not pick up the very thin bottle geometry. Any ideas on how to make this work properly? Or should I just sim both things one after the other? Assuming the water would not have an massive effect on the behaviour of the Glass? Thanks so much for any help in Advance! Hipnc attached. WaterInBottle_003.hipnc
  23. I am new to the packed primative RBD in H14 and have found some examples of sops level activation, but how do i make an rbd packed primative active based on a hit or force value? For example a sphere hitting a cut up box suspended in the air? Here is a basic scene. I have attempted to use the sop solver but i just don't get it. Thanks.
  24. Shattering an animated object in houdini 14

    hi guys, I've been working on a shot of my own where a aircraft crashes on the Ground ( reference - airplane crashing scene from KNOWING) . I am aware of the prefracturing process of vornoi and till now I usually worked on static objects so this one is already animated in maya. I got the plain obj seq in Houdini just figuring out how to shatter while the animation still goes on. Found a very less articles about it . Have a very faint idea that its something related to dynamic constraints! can anyone enlighten me about it or any tutorial link for it? Thanks already!
  25. I have a RBD sim, with 1 packed object which contains 9 elements. I am trying to disable the gravity only on certain elements, within the packed object. In order to achieve this, I would like to control the gravity node with a dop group. I created a point attribute "falling" which I control in a sop solver, within the dop network. Then I created a DOP Group that creates a group based on the following expression: point($DOPNET+":"+$OBJID+"/Geometry",$OBJ,"falling",0) Now, this seems to work but ...not quite. I see elements that start fluctuating at a certain moment, but this moment doesn't match the moment when the "falling" attribute is triggered to 0. To start, I'd like to understand if I am using the above expression correctly. I am quite confused with the global variables $OBJID , $OBJ used with Packed Objects. Could anyone shed some light on this? I am on H13.0.547
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