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Found 140 results

  1. 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
  2. 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!
  3. Finished my first tutorial, hopefully you find it helpful learning Houdini!
  4. 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
  5. 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
  6. 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
  7. 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!
  8. 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.
  9. 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
  10. 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
  11. 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?
  12. 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?
  13. 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.
  14. 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.
  15. 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.
  16. 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?
  17. 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
  18. 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
  19. 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
  20. Hello everyone, I'm hoping this is a super easy one, and I'm just missing something simple. I'm reading in an attribute into a vellum sim, to use it as a falloff for some forces. The problem is it's only reading the attribute on the first frame. I'd like to be able to read in these attributes every frame, to adjust the falloff. I've attached the hip to illustrate the issue. Any help would be greatly appreciated! Cheers! AttributeUpdateDOPs.hiplc
  21. Hey all, it's first post here and new to Houdini so I appologise if this isnt the easiest to follow. I have been trying to create a robust system for controlling vornoi fracture points, their glue strength and a way of manually breaking constraints between points. Ive been following some tutorials piecing together relevant bits from each to try and achieve this. My current issue Im facing is that once I play the simulation and the constraints start breaking they start flickering back on and glueing parts of the object which have already been broken. From my undertanding I think the manual breaking of constraints which is conflicting with the remove_broken SOP solver within DOPs, but I can't figure out how to get them both to work together. Any help would be greatly appreciated as I've hit a brick wall with this. Ive provided my scene file - I hope it's all easy to undertand. Thanks. Fracture_v001_notworking.hiplc
  22. FLIP-Pyro Interaction Tutorial

    Hey folks - long time lurker joining the party with a tutorial showing a workflow for integrating the FLIP and pyro solvers, allowing for bidirectional interactions. I cover a few other tips and tricks along the way, so I hope you find it useful! Hip file attached (and linked through from the video). flippyro_diffusefx.hiplc
  23. I'm hoping this is a fairly simple one, but I'm beating my head against the screen which doesn't seem to help ;-) I'm working on a scene with a large number of various bottles and trays in a simple dynamics simulation. All bottles can be simulated as tubes, all trays as boxes. Simple enough. What I can't seem to work out is an efficient way of instancing high-res bottles, trays etc over the proxy geo. My first idea is using an instance SOP with a 'DOP Import' node to give me the positions, using 'create points to represent objects', then varying the path with s@instance="obj/bottle1" etc; but although the points all seem to transfer fine, with data intact, the instances don't follow the point positions properly - the instances all come in at the origin of the sim and then explode out from there. I'm guessing I need to correct the first p/s/r values for each instance... but that's where I've ground to a halt. Hope someone can help! I'll upload where I've got to if that helps. Cheers -Chris
  24. FLIP substeps for fast moving boat

    Hello dear odforce users. I have a question regarding substepping with fast moving colliders. I have a catamaran speed boat which is driving in a straight line at roughly 60km/h. I added some procedural animation to the boat with the help of the ocean spectrum, that drives the wavetank, and CHOPs. Currently the simulation uses 6/8 Substeps on the FLIP Solver and the Solver has access to the sub-frame collision geometry. The problem I'm running into is that the trail left by the boats keels has visible stepping in position and velocity, which causes tendrils to shoot up in the boats wake. This doesn't look good together with motion blur. Should I increase substeps further to get rid of the stepping by brute force? Work out a whitewater setup to mask this behavior? Or is there anything else you can recommend in this case? I'm thankful for any suggestions. P.S. Unfortunatly I can't provide any scene files
  25. Hello, I'm sure my title for this post could be clearer, so for visualization purposes, say I have a field of discs that are RBD Packed Objects on the XZ plane, and above them there's a sphere with gravity: Normally the sphere would fall onto the discs and the discs would act more or less like a ground object, but I'm trying to have the discs raise up depending on each one's respective distance to the sphere. So far I've found that the positions of the discs (RBD Packed Objects) can be controlled in a sop solver within the dopnet, but I have no idea how to reference the position of the simulated geometry (the sphere) to inform the discs' positions. Can anyone show me the way? My ultimate goal is to eventually replicate the desired effect with the sphere being a vellum object.. would that require a different workflow? Here's my setup so far that may or may not save you a minute: sample.hipnc Thanks for taking a look!