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Found 146 results

  1. I have a basic dops ( vellum to be specific) and i want to add elements dynamically to the sim. in the example > case1 , i create an random line and add it as a vellum hair into the sim .. and this seems to work. case2 and case3: i want to access the current frame of The Dops sim, and i create a line from a fixed point to a point on the mesh( think lightening ) .. but doesnt work. cant seem to access the current mesh and create a line(s) and adding it back to the sim.. any tips and pointers would be appreciated. thanks sideFx.hipnc
  2. Geo appearing twice in Dops

    hi guys, I have a vellum balloon constraint on my geo. Until there, everything working ok when I press play. I have added an Attach To Geo Constraint inside the dopnet and now, my geo is doubling up when I simulate. One of them behaves with the added constraint and the other one without. Whats wring? Tx
  3. Vellum Pressure

    Hi, I wanted to ask about some of the hidden intricacies of vellum pressure. In particular I recently found out about the @pressuregradient attribute that determines the direction in which the object expands as pressure is applied. I wonder: How is it determined? I suspect something to do with Normals, but then when I visualise the attribute it tends to always have a rough relationship with {0,0,0} - why? This leads to strange inflation especially if an object is off-center and then it trends away from the origin, as opposed to away from its center of mass... Can it be manipulated in the solver? It would be nice to procedurally predetermine the inflate direction, although I'm not sure how to access or manipulate this attribute. Can it be manipulated per frame? If I have multiple objects that start in a rest position and their inflations happen one after another - one ball moves other balls out of rest position for example... Then once the ball that has already been moved starts to inflate, is it computing on the pressure attribute given at the start of the solve, or the one at it's current frame number? I could probably word these questions better and I do apologise, but at the moment it seems I have run out of places/videos to read/listen to. Thanks a lot for your help! Cheers.
  4. Hi. I am trying to make a simple HDA which will drop down an asset on another asset. It works fine inside Houdini but it doesn't work in UE4 or Max. What is wrong with current setup? drop_dop.hda
  5. Wire constraint network Question

    Hi all- Building a procedural constraint network for wires by connecting the interior points in a grid. It works fine for some grid dimensions, but not others, where the sim blows up. shown below a 5x5 and a 6x6 grid. A 15x15 grid will work fine, but a 6x6 one won't. Curious! I'm building zero-length constraints from the interior points and setting the anchor points as follows: int wirepts[] = nearpoints(1,@P,.0001); foreach (int wpt; wirepts) { if(wpt != wirepts[0]) { int pt1 = addpoint(0,v@P); int pt2 = addpoint(0,v@P); setpointattrib(0,"anchor_id",pt1,wirepts[0]); setpointattrib(0,"anchor_id",pt2,wpt); int newprim = addprim(0,"polyline",pt1,pt2); setprimattrib(0,"constraint_name",newprim, "WireGlue"); setprimattrib(0,"constraint_type",newprim, "position"); } } setpointgroup(0,"delete",@ptnum,1,"set"); I delete the original points later - I'm not using the first of the nearpoints to avoid a prim with the same anchor points, I thought that might be the problem, but it didn't seem to matter. Does anybody know the reason why this happens? Am I missing something? Thanks - I'm including a sample file. wireGridConstraints.hiplc
  6. Grouping DOP objects by Impact?

    Hi, First time posting here and relatively new to Houdini, so please forgive any poor use of terminology etc. Basically I want to group DOP objects, specifically RBD pieces, when they are impacted by another object. I want to do this so I can add gravity to each piece as they are impacted. When I look at the geometry spreadsheet I can see the Impacts data appear, but I don't know how to then group these objects by this. If it helps to visualize what I mean, I've made this puzzle globe made of 500+ pieces, and I'm throwing this ball at it to break it apart. I've got my sim working well enough, but currently gravity is not acting on any of the pieces, so when the ball hits, it's breaking the pieces apart but they are acting as if in zero gravity. So now I want to group this pieces as they become impacted either by the ball, or the pieces next to it, so hopefully by the ends all of the ball collapses. Thanks for any help, Alex
  7. Vellum Collision Problems

    Hello! I am trying to deepen my understansing of vellum by building the solver netowork myself. I have hit is very enfuriating sustuation were my character litterally walks out of her pants. When I use the sop based solver this dosn't happen. I am sure I am missing something but it seems most things I have tried are giving me the same result. I am using an almebic cache for the collider, and cloth geometry brought in from Marvelios Designer. I am using an collision source node to generate a vdb for collisions, and using a staticObject set to “Use Volume Collision” and “Volume Sample” for division Method. Here is what I am getting
  8. I'm trying to create a Python UI state that returns the currents fields in a DOP network. I want to query the fields and then store there values so that I can print it in the viewport. I can find all the python documentation to get the fields themselves, but I can't seem to find out how to get the values stored in the voxels. I know it can be done in SOPs, but I really want to do it directly in DOPs. Is this possible? FYI, just using a simple Sparse Pyro Shelf tool for my testing. I want to query the density and temperature fields and calculate the maximum value stored in those fields. Thanks!
  9. Finished my first tutorial, hopefully you find it helpful learning Houdini!
  10. save particle velocities every frame

    Hi All, TL;DR - How do you save particle velocities each frame to feedback into a sim? I'm working on a particle effect for rain on a window. Currently adapting a nice example from Toadstorm. I've made some changes to his setup. He has new particles growing over time and becoming droplets past a certain pscale, so i've derived mass from pscale to connect droplet size and speed, as the wind force i'm using to move them is not set to ignore mass. video I added a sop solver after the DOP to delete still particles touched by moving ones. And a popinteract and a popfluid to try and get the moving drops to coalesce and follow each other as they move down, but this has only slightly worked. Ideally i'd like to write the velocities of the moving drops into a volume which could then come back into the sim the advect the particles, or some other technique that follow make it so that new drops hitting and existing trail would follow its path precisely, and add a little to their speed and size. I presume I would use a sop solver inside my DOP network for this, but no clue beyond that. Any advice much appreciated, H windowdrops-uv3-w.mp4
  11. Hey, I've been stumped on this for a long time now and cant find any more useful resources online. I've been trying to dynamically add vellum patches over time for a project of mine. In the attached video you can see my current result, which is done by switching between the sopsolver that creates the golem, and the vellum solver that makes them go stringy. Ideally I'd like for vellum to take over for each worm as soon as the sopsolver is done growing it, thus on attribute presence. Hopefully someone can give me a point in the right direction. Thanks in advance! Wormguy.3.mp4
  12. I have a vellum cloth object set up in DOPs. I want to add an animated pin to target constraint. I can get this working in vellum solver SOP just fine, but I can't figure out how to set it up inside a dopnet. I've tried setting this up multiple ways, and I'm not sure what I'm doing wrong. (HIP and screenshots attached.) I would also like to know how to specify target geometry in DOPs. dops_pin_example.hipnc
  13. Hi! I seem to be having a small issue with the 'transform pieces' SOP not working as it should. I have a mixamo animation that I have fractured and I use a 'point deform' to get the animation back onto the fractured geo. I want to use the 'transform pieces' SOP to convert my proxy geo to my hi res geo. Whenever I do that the whole thing freaks out. I have also tried freezing the pivot and copying it back to the 'dop import' points. Using the rest points does not work either. If anyone knows how to solve this problem then please let me know! Thanks in advance!
  14. Hit data in SOPs

    Hi, As the title says, I'm trying to make hit data in sops. To expand on that I have a sequence of points moving through a piece of geometry and I would like to create a point that lasts for one frame at the point of intersection on the geometry. Is this possible? I have a rough setup that uses nearestpoint and fuse, but the points I am getting are not accurate enough for what I am trying to accomplish. Mostly because the moving points are very fast and all have random speed. Any help would be greatly appreciated. Thanks in advance.
  15. hey... I had an idea of directly fitting in the whitewater source via a sop solver in dops as a post solve, is this possible? I have tried it. but with no luck, also by applying a compress fluid. before Im gonna send scenes Im just wondering. And about the experience. was trying to get some more fluids overtime to fill gaps like you would do in a sopsolver in dops thnx
  16. Hey all, I'm trying to play with a scene where I'm doing some explosions on a beach and I wanted to make sure I had all of the individual effects down before I started trying to do the large scene. I already figured out how I want to do the explosions with a sparse pyro, and I got the grains solver to behave how I want for the sand to be kicked up, but when I tried to add a pyro solver to the sand grains I got some weird results, so I went to make a simple example scene that would be faster to simulate and it started doing even worse stuff. My grains scene is giving me some really bad smoke that doesn't seem to be advecting and is only generating on each frame of my cached grains. Seeing this, I found an example file which was using a pops simulation to generate smoke, so I tried to apply what was in there to a simple test scene, and for some reason my sims are applying giant black box sprites to the particles before it even gets into the pyro simulation. If you have some advice on how to handle the dust from sand explosion that would be great. If you have any idea why I'm getting the sprites, that would be amazing as well. The files aren't the cleanest, but here they are. I am using GridMarkets caching and rendering for the sand file, so if you don't have their nodes you can just delete them and replace them with filecache nodes. SandboxPop.hip pyroFromParticles.hip
  17. Hi guys, I have a rigid body sim with constraint network, I want to access the previous frame and current frame data of the constraints (impact, forces etc) inside a sop solver in DOPs. Currently when I call the attribute in a wrangle from the relationship geometry node I don't know if it's current frame data or previous frame. How to get both the current and previous frame data in a wrangle in sop solver in dops?
  18. I'm looking for alternative workflows for defining attributes on a tet mesh for FEM simulation. Normally I would use intersecting volumes to define regions inside a tet mesh. But for my current purposes that would require producing some pretty complex geometry. The ability to paint these attributes would be simpler. For instance, it might be nice to be able to paint an attribute on the surface and have it penetrate the tet points at a given depth. (Though even if that were possible, I'm not sure how you would access deeply interior points that are not close enough to the surface.) What methods do you use for assigning attributes to a tet mesh?
  19. Bonjour, hope you all doing great. i can't get an alembic geo to be simulated in dops .. however if i made a simple animated geo with keyframe animation,i can switch from being active in dops and reading the animation but it doesn't work with alembic.. should i be baking the alembic to keyframes or how it works? Thank you.
  20. I'm building a relatively complex Vellum DOP setup using multiple objects with different constraint arrangements. The issue I'm having is my usual Achilles heel with this sort of thing: modifying attributes and values mid-sim. My specific issue is that I have a Vellum cloth object that is using the Pin to Target constraint option to follow some geometry I'm animating in SOPs. I created a point attribute for the target weights and that's working fine. My problem is that around halfway through the sim I want to animate down the target influence for this specific pin constraint. I have partially solved the problem using the Vellum Constraint Property DOP and animating the "Remove" value from 0 to 1 at the frame I want the pins to disengage. This works nicely as long as you're careful to select the specific constraint geo in the Group field of that DOP it will work. It's working so I'm going to get through this project using this method, but I'm having a really hard time figuring out how to modify my existing per-point constraint values using these fields. My questions: There are a bunch of specific vellum constraint attributes represented like Stiffness, Damping Ratio, etc. in the Vellum Constraint Property DOP that I can play with over time. Are these scalars that multiply by the point attributes I already have? Or are they values that will override the ones I've already set? Assuming they are overrides, is this why the VEXpression toggle and field is there? If I do something like "stiffness=stiffness*(fit($FF,50,100,0,1)" will this remember the original value of stiffness or is that being reset each frame? There is also the SOP solver methodology where I can modify the definition of the Constraint Geo over time. I can always fall back on that but it's also kind of tricky to setup. Hoping for something simple and effective that can just be wired into my DOP network. I really rely on the Sidefx example files to guide me through a lot of these setups, but I find that these kinds of constraint modification setups are in short supply. Would love to know how everyone handles this sort of thing. If anyone has guidance on this sort of thing, let's discuss. Thanks community.
  21. Why does the attribute noise on velocity cause the whole simulation to go in one specific direction? and I'm not even able to change the direction, it's always the same. Here are screen shots with the attribnoise enabled, then disabled and the pyro solver settings. How do I tell that attrib noise not to go in that direction? I've changed its settings but it doesn't change direction. Even if I change the source geometry behind the smoke, even if I rotate the source, the direction stays the same.
  22. I'm trying to understand how to assign colliders to objects in a vellum simulation. For example, I would like to add a collider that only grains will collide with, while the collider is ignored by other objects in the simulation. This helpful solution shows how to accomplish this with a dopnet setup. (A screenshot of this approach is below.) However, I don't know whether it's possible to send the output of the dopnet to Vellum IO and Vellum Postprocess. Is there another way around this? Or perhaps a way to control collisions from within the vellum sop solver?
  23. Kill particles by distance

    Hi all, I'm trying to come up with some vex to use to kill particles in a sim when they have traveled a certain distance from their birth location. I have mother particles that last one frame and i'm using a pop replicate to spawn new splash particles from them. What i'd like to do is store the position of the mother particles and subtract it from the position of each replicated particle every frame to get the distance, then set them as dead once this has passed a given threshold. Extremely limited VEX experience here, so if anyone could give me some kind of starting hint/snippet that would be amazing Many thanks, H
  25. Transfer Low to high sim - vellum

    Hello, i have a vellum source emitting a low res model every 10 frames. How can i exchange the low res output with the high res version? this is my setup, i am working on Houdini 17