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Found 213 results

  1. As you can see the surface filtering doesn't work due to a lack of level-set grid. Is there a node to change the VDB or add the level-set grid to a VDB?
  2. Hi, I am having a question about collider type option in vdb projection nondivergent SOP. A basic method is working well, and I try to use input2's optional collider VDB slot with collider type. I am expecting projection of non-divergence should happen only outside of collider or get influence of collider's velocity. However, it's nothing happen or getting error. I am guessing input2 should have a certain format to plug in object. If anyone knows how to use that feature properly, I would appreciate it, thanks!
  3. Hey guys, just a simple question. when should I use VDB and when should I use standard volume? I noticed that in older versions of Houdini, the VDB doesn't seem to be able to be used in dynamics simulations.
  4. Hey guys, I've always liked the works of Daniel Arsham. He tends to do a lot of eroded pieces with some sort of crystals, usually. I was wondering if anyone had suggestions on how I can create stuff like the pictures below in Houdini. I have used booleans in c4d with a displaced sphere/object but found it not looking as detailed/nice as I would have liked. It also takes quite a bit of time to create each individual object that's put in the boolean. In Houdini, I thought of converting geometry to a VDB then putting it in a volume VOP with some sort of noise and subtracting it from the volume, then converting back to geo. But I'm not too experienced with Houdini tbh and was looking for suggestions on the details of a potential setup.
  5. Hello, I am trying to make a shelled object with a thickness (so negative space outside and inside, but the thin shell is positive space for collisions) collide with a FLIP fluid sim. Essentially imagine an egg with some fluid inside. The fluid would stay inside until cracked. After that point the water spills out and the collisions of the shell are all accurate before and after the crack. The problem im facing is that VDB creates only either a fully encased volume where anything thats inside the egg is negative and outside is positive or vice versa. I cant seem to make it recognize that the shell is the only thing it should be making a VDB volume out of and treating everything else as the outside. I can turn on the invert sign on the collision for FLIP and it kinda works but then once the egg cracks it just all goes haywire. So Im not sure how to approach this. I have also tried to create two VDBs with slight offset and combine them with the multiply function. Which in volume slice shows as a narrow band but the FLIP particles dont seem to like it at all. I have attached a simple file to show what's happening. Water_test.hiplc
  6. Is there an easy way to blend two vdbs using for example a gradient on the Y axis? i have a displaced fog vdb and i want the displacement to happen in a certain area. Can i control that with a mask somehow inside the volume vop or do i need to blend the fog vdb without the displacement? Any workflow tips?
  7. Hi guys. I'd like to have 2, maybe 3 colors of paint swirling in the blob. How do I go about that? Attached is the hiplj_paintblob_flipsim_test (1).hiplc file.
  8. Hi! I have a question about VDB vel. Let's say there is a a "cached VDB" sdf and vel where vel exists only around surface. Then I try to fill out vel inside. If you have a good idea, let me know, thanks!! (sorry, I uploaded the same pic by mistake, and cannot get rid of that...)
  9. Hi, I am trying to figure out how to use VDB Project Non-Divergent > Collider Type. I am expecting input1's vel will react/bend against Input2 volume. So far it's possibly working with Collider Type > Bounding Box. However, when using Collider Type > static VDB and Dynamic VDB, there is no change in input1's vel field. Also, I am not sure what volume name should select in Collider Type > Collider. It would be surface or vel ?? If anyone knows how to use static/dynamic VDB collider with input2 properly, I appreciate that, thanks ! Hi,
  10. I have a dataset that contains animated volumetric smoke density. The dataset is stored as NPZ files (numpy array save file). How can I load the density of a saved smoke simulation as an animated volume to render it ? For context about the float data in the volumes. This is what simulation number 70 snapshot 150 looks like in matplotlib with a viridis color map, but the data in each voxel are simple float64 values. The other snapshops and simulations look similar. This is how you load a single npz file, if you want to try it with the dataset. It just generates a generic numpy float array. So you could just make a tiny numpy array filled with random data yourself for the purpose of testing like this np.random.rand(3,3,3). import numpy as np def npz_to_nparray(filepath): """ loads npz file from location :param filepath: string to file location :return: numpy array """ data = np.load(filepath) data = data[data.files[0]] # normal strange operations to get the the actual array inside data = np.transpose(data, (3, 1, 0, 2)) # turning the inner array layer outside and rightside up return data[0] I have tried: -I can load the npz files in python and in Houdini's python shell as a numpy array. I dont know how to put the data into a Houdini volume or which file format Houdini needs to import it. -I tried to translate the npz files to vdb with the pyopenvdb libary for python. But after multiple days of trying I am unable to import pyopenvdb. I build pyopenvdb library on windows with vcpkg and cmake, but I cannot import the build package. I setup an ubuntu VM and tried importing pyopenvdb there, but I can not import it. tl;dr: How to import animated smoke voxel data that is currently stored as a 4D python array?
  11. Hi, I am in the process of setting up a sky full of clouds - using VDBs. I have set up an early proof-of-concept test, can render it, and it all works out of the box. What I'm struggling with is how to maximally optimize it. I have seen an Arnold setup in Houdini, similar to mine, with 3000 cloud objects - using ass files and rendering an HD1080 frame in around 5 minutes, and using less than 100Mb of memory. Pretty efficient! My Redshift test, has a similar number of VDBs exported out as a single rs proxy which is then instanced across scattered points on a grid. I expected this to speed up the rendering process significantly. Sadly, it actually takes over 4 hours at the same resolution and uses more than 5Gb of memory! What I want to do is leverage the power of proxies and instancing to render this setup and at least match what can be done in Arnold - Redshift is after all a definitively faster render engine. Does anyone know an efficient and effective workflow for this type of solution please? I feel like I've missed something here; as usually Redshift is very fast. Many Thanks, Scott
  12. At 13:52, this video briefly glosses over using simple geometry to add temperature to a specific area of an explosion: This is pretty much exactly what I want to achieve. The setup looks simple enough, except for an attribute wrangle where he doesn't show what's happening. Does anyone have any idea how he might be doing this? (Any other methods are welcome too!)
  13. Thanks in advance for the help! I'm advecting a vdb so it grows over time. Once turned back into polygons, I'm hoping to stick UV's on it. The setup - I promote my uv's to point attribute and in the initial "VDB from polygons" I created a new surface attribute to store the uvs - I advect both vdb volumes in a sop solver, and then convert the vdb to polygons. - I then use an "attribute from volume" node to transfer the uv's from the volume onto the mesh. This works for the first frame, but as expected distorts and breaks down pretty quickly as the volume grows. I've researched and found examples of using the "dual rest fields" option in the Pyro and Flip Solver and then blending between the two rest states to "reset" the texture distortion as the mesh grows. There is a great example of this by Jesper Rahlff here (https://forums.odforce.net/topic/49461-lava-flow-question/?do=findComment&comment=227475). Great! I can create a rest field but... - What exactly is rest2? how is it different from rest1? - And how would I go about setting it up here without using the pyro or flip solver? If you have a better way to achieve this always open to that too VDB_Advect_UV_rnd_v02.hiplc
  14. This is more of a minor annoyance than anything else, but I'm working through part 3 of that free Rebelway asset creation course and around 9:30 I noticed a different behavior than in the video when trying to shade a VDB fog in the viewport with standard distant lights. It seems like the light gets cut off at the surface of the volume, and as far as I can tell it's not caused by the Arnold lights or anything else in the scene. The set up is super basic, and the same thing happens when building the scene from scratch in new projects. That said, it would be nice to have lights interacting properly with the fog, so I thought I'd ask to see if anyone has any idea what might be causing that. I know that this masterclass was created in a much older version of Houdini, perhaps as early as 16.5, so I imagine it might be a version difference, but it seems like a silly behavior to change. Might it be a bug? It still happens after updating Houdini...
  15. VDB and Noise in Houdini

    Hello Everyone, Welcome to VDB and noise in Houdini. This series will teach you how to generate a variety or organic and inorganic shapes and structures using VDB and the various procedural noise maps and textures available in Houdini. https://www.rohandalvi.net/vdb
  16. How to export vdb's in the right way

    Hello, I have a massive smoke simulation going on, and now I want to export this simulation in vdb's, to import them into a another 3d software (Blender). But when I click on the cache button or render to disk button, everything goes well, until frame 70 +-10 frames or so.. and then it stops because I am getting out or RAM. As I have 64 GB RAM, I would love if someone could explain me, how can I export the whole simulation, without decreasing the smoke division size... or smoke quality! I have tried to just export the density field, but then the smoke looks kinda low res and only if I am exporting ALL pyro fields, like: density, temperature, fuel, vel x, vel z, vel y.... and so on, then the smoke is high-res in Blender. But if I am exporting all fields, then it stops after frame 70 because of the RAM... is it possible to cut this simulation in parts and exporting them seperatly or somehow optimizing the fields or the pyro sim or vdb's so that I can export the whole simulation without any problems AND in high-res quality? Thanks for advance Daniel
  17. Hi everyone, I've an issue with vdb and i can"t find a way to solve this (so that's why i'm here haha) I'm working on a fluid simulation and i need to get the mesh into vdb to use it as collision surface. I'm trying to get a polygon mesh into vdb with the node vdb from polygone but there is holes and artefacts.. the issue is when i'm converting polygons into vdb with vdb from polygons there is a lot of holes into the vdb and I can't use it for my sim ( the particles goes through it). I think the problem comes from the mesh but I can't find what it is. (the mesh comes from Zbrush) I tried with a collision source node, same result as vdb from polygons. I can't find a way to get a clean vdb fron this mesh. So I wonder where those holes coming from and how can I fix it ? If someone have the solution, that will be great =D thanks a lot !
  18. Masking Volume Noise?

    hey folks. I've been following this amazing tutorial by Tim J but wanted to learn how to add attribute paint or another noise to use as a mask so only certain areas are effected by the volumetric noise I'm quite new to Houdini and have no idea! thanks in advance.
  19. Hey Guys, I came across a problem when simulation a vdb-mesh-transition and i was wondering what the proper workflow would be to replace my final mesh (the text in this case) with the text-mesh i was initially beginning with. I've read about point deform but this SOP didnt help me at all.. Im sure there must be a way to replace it in the right way but im just stuck like the total beginner i am.. I would appreciate any kind of help or direction very much!
  20. Flickering Liquid

    Hi there! I have this melting setup with a POP solver, basically scattering some points onto the original mesh and then melting then and meshing back everything again using "particlefluidsurface". So I have been trying to get rid of this flickering on the mesh, I have over 500k points and I also tried increasing the samples and playing with the particle separation in the "particlefluidsurface" I also tried using "vdbfromparticles" but its more or less the same result. I want to know if there is anything I can do to help reduce the flickering? Any help on this is much appreciated Thanks in advance untitled10.mp4
  21. Hello guys, I am desperate on this one! I want to fill with water this evolving shape that starts from nothing and expand like a flower. The idea is to make the fluid squirt out of it from the top (there is a hole on the top of the geo) but to start, I was thinking of filling the geo first. Maybe there are other ways to get the squirt going but I would like to fill the shape with liquid first. I am aware that I should use deforming VDB object for collision, I know the workflow but there is definitely something I don't know here. Whatever I do, the liquid goes through. I tried with a super high res VDB or even 8 substeps, nothing works. I suppose it will be easier if I attach the file so here it is test_ffluid_inside_growing_geo.hip Any idea? Thank you very much
  22. Hi there, As you can see on the video attached, my VDB is jumping from being fine to suddenly being almost gone, and then appearing again. What could be happening? The geometry that has been turned into a VDB has a fixed number of points. It was a curve fed into a revolveSOP, curve has been resampled to a fixed number and then that curve is scaled. Thats why the number of points is not changing. I am mentioning this because maybe it matters, but it probably doesn't. I don't know! If anyone knows how to fix this, that would be awesome!!! Thanks 2021-07-08 17-06-31.mkv2021-07-08 17-06-31.mkv
  23. dust Clump using VDB

    Any effective way to create this kind of dust. I used Cloud noise but doesn't seem to look preety well. any suggestion will be helpful. Thanks
  24. Hey wizards I have problems with exporting instanced scattered VDB clouds( they build a cloudscape). When i try to put a ROP geometry or a ROP alembic node at the end of the chain it doesnt work... My Goal is to export the "cloudscape" as a single vdb file to use that in 3ds max with vray for Production. Can anyone explain how to properly do that? Thanks in advance ;-) Cheers, Marcel
  25. Hello good people! So I have a few questions about VDB, mostly about things that I never cared about - until I had to. - Why are there translations on the fields of a VDB ? Most render engines do not seem to care, except for Vray. Vray apparently requires all those translatations to be the same for some reason - or else it will generate huge bounding boxes in Maya, and maybe even wrongly sample velocity. Resampling fields will "freeze" those transformations but I never had to do it with Arnold, RS, 3delight or Mantra. For extra giggle, putting a simple point wrangle with @P=0 apparently emulates how Vray see things. - Why can't I get rid of the "dopobject" and Cd attributes when saving to file ? The dopobject attribute is only added when importing the fields with a dopimport fields and not with an object merge. But with the dopimport it just keeps coming back from god knows where, and it makes no sense. - With Vray, am I stuck with having to use the same voxel size for all fields, including Vel, which can in turn creater HUGE files ? Doc indicates Vray can't handle vector fields and I can drop a vdb vector split, but there is nothing about voxel size. I have to accumulate tons of tricks to try and lower the file size. A 250mb VDB file with vel resampled to twice the voxel size can turn into a 1gb file with vel at the original voxel size - and because of how vray handles preview in the viewport, this is unbearable. Alternative is throwing the volume quality through the window to try and hope to reduce file size. I'll include a simple scene file with a few scenarios and oddities which just illustrate those quirks. As I said I usually have no issues but complaints from the Maya Vray departement upon long loading/refresh times ( even for mere 250mb files ) or motion blur not working forced me to approach things very differently... VDB_savingToFile.hip
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