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Found 202 results

  1. Hi guys, I have an issue with visible banding artifacts both in a pyro sim and in a volume generated from polygons with iso offset. The artifacts appear as soon as I crank up the density. The source geo for the static volume is the same as the collider geo for the pyro sim, everything is at the same (high) voxel resolution and from the same highres poygon base geo. Does anybody here know this issue?
  2. 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?
  3. 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!)
  4. Ripple solver to transfer velocity information

    Hello! I am building a flocking sim, and I am trying to get the turn information to propagate across the flock like a wave. I am using particles as "birds", so each particle represents a bird. I am trying to figure out how to use a ripple solver that uses a volume to broadcast the velocity information of each particle at each time step out to the rest of the flock, so that the turn information moves through the flock in a wave-like fashion. LMK if that makes sense and if you have any suggestions! Right now I just don't know how to read the velocity information of a particle into the ripple solver, and then ripple that information out to the other particles. Thanks!
  5. Hi all, I generated a mesh, which I converted in volume, then used a box with vdb combine to limit my volume to that box. Problem is near the bounds, the density is fading away. Is there a way to avoid this and keep true density? Thank you, mrblimack
  6. 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.
  7. Hi guys. In a smoke simulation, I want to use a thin deforming geometry (a sheet) as the collision object, but instead of creating a Volume, I want to use "Point Velocity For Collisions". Is it possible? Thanks for helping. Smoke_CollisionPoints.hip
  8. Houdini.School Velocity Forces

    I am happy to announce that https://www.houdini.school has launched and you can get 15% off now through July 27th, 2021. I'll be joining a host of talented Houdini teachers, like: Debra Isaac Kate Xagoraris Beck Selmes Christopher Rutledge Justin Dykhouse Jeffy Mathew Philip Nicholas Ralabate You can learn more about my Velocity Forces class here: https://bit.ly/houdinivelocityforces Teaser video for my Velocity Forces live class: https://vimeo.com/577928177
  9. Gas Disturbance

    Hello, Following a tutorial about dynamic cloud simulation i get weird result applying Gas Disturbance operator since in houdini 18.5 have different parameter and totally different behaviour that what showed in the course (recorded in H17.5.258 ), any hint on how to set it so it behave like older version? In specific: Binding have not "Disturb field is vector field" option "Cutoff" parm in Disturb setting mode "Block based" have now a lot of new parameter realted to noise that doesn't exist in older version Control setting doesn't have "Control influence " parm Thnks!!
  10. Hi everyone! I'm struggling to get rid of those sharp voxels in the sim. I have a pyro solver, and I have tried increasing a lot the res in the Volume Object, Volume Rasterize Attrib, Points from Volume, increasing substeps, also the collider has a very decent mesh and it's also subdivided. I also tried using the collision object as a proxy vdb, and also using it as a collision volume inside the pyro solver. It's been very frustrating. I also found other posts with the same question, but still without any luck after all I have tried. I know the collision object may be causing all of this voxelization, but I keep on increasing the res, and I'm still getting the same results. Any help on this will be much appreciated! Thanks untitled6.mp4
  11. Hi everyone. I have a very basic setup and a problem that can't solve. I cant transfer "density" attribute from volume to particles using POP ATTRIBUTE FROM VOLUME. But I can't transfer color, though it should work in a same way as density attribute transfer. I include here printscreeens so you can see easily. I create te volume, assign color with color SOP. Refer to this color sop within POP ATTRIBUTE FROM VOLUME, refer to Cd as a name of a volume and.... nothink works(. Thank you in a advance.
  12. Volume Advection

    Hey everyone, I'm advecting this density field with the velocity field using a for loop, and if I crank up the iteration the density starts to clip. Do you have any idea how to prevent that? volume_advection_clipping.hiplc
  13. Hey all I have some low-ish resolution VDB dust clouds created in C4D with the TurbulenceFD plugin. These contain velocity channels. So far, I'm just not satisfied with the overall detail. What I've done to try and increase detail is convert the VDBs to Volumes, Volume Resample them, then use Volume Velocity to add some curl noise. It's looks OK, but by no means what you would call a true Up-res, that uses existing velocity channels to increase detail in turbulent areas... So that's the question really. How do I take a pre-calculated VDB (not dynamic at all) and give it a high-res makeover? Any pointers would be appreciated. Please be aware that the overall motion has been signed off, so all that I should be changing at this point is detail. I would just do the Up-res in TurbulenceFD, but it's buggy as hell and wont work. Every day I get closer to ditching C4D entirely. Thanks!
  14. Hi, im trying to render a simple pyro explosion with Vray. My steps are pretty simple for now: I added a pyro sim from the shelf tools to my scene gave the sim a material that has the Volume Grid shader https://imgur.com/a/rdjdjtY This is what i end up with. Inside the Volume Grid under Fields i enable Fire, and use the flame attribute, but nothing changes. I have full controll over the Smoke parameters in the Smoke tab, but nothing changes when adjusting parameters in the Fire Tab. Here are my Volume Grid Settings: https://imgur.com/a/kBtFDZm Im sure im just forgetting a step or something. I would appreciate any help. Thanks! pyro_vray_test.hiplc
  15. Hey there, After spending a fair amount of time on SOP and VEX, I'm now learning basic volumes handling. I found a behavior I don't really understand and can't find any ressources on the subject. I created a simple setup to change the density of a scalar volume with the distance to a point. Everything works as expected, but when I move the point to a bound of the volume, the density from on side seems to be "reflected" on the other side of this volume. Looking at the screenshot, we should only get yellow values on the left (where the point is), the right side should be blue. Seems to me there are three possibilities here: - My volume wrangle might be wrong, - There is something I didn't understand about volumes, - There is something wrong with the way I setuped the volume visualization. Can someone explain what I didn't get right? Thanks strange_density.hip
  16. Hi guys I have a cloud volume render problem. I creat a instance VDB cloud and use ass to arnold render But in some places there appeared undesirable lines I will not have this error when I test in a single cloud and I only use standard_volume as the Shading I am also sure that there are no lights in these directions(2 arnold light) The horizontal or straight line in the image below is my problem I don't know how it is caused, is there any solution?
  17. I need to get clean glowing Volume Lighting AOV in Redshift. First attached image is what I have in renderview - it's precisely what I want. Second one is what I get once I have my EXR. I dont need all this smoke. How do i fix it?
  18. Hi all, i'm trying to render volume with redshift but my render look lowres compared with the viewport on the left. Could somebody please help? Thanks! nebulaR&D_v01.hiplc
  19. Rendering thin lines Mantra

    Hi all, Recently I have been trying to understand a bit more about rendering. I was trying to achieve something similar with Mantra. My approach from past experience would be running a pop sim and drawing lines out of the particles to create straight trails as the picture shows. I would then volumerasterizeattributes an attribute like curveu which is ramped to control the intensity along the curve. It would essentially create a volume to render in Mantra and then use Micropolygon rendering to render the volume slightly faster than PBR. I would use a pyroshader and would wire the rasterized attribute into the temperature and density to give it some intensityand color. What I can't seem to achieve is these thin lines that are shown on the photo, I end up with a very thick individual lines in the volume regardless how low I push the pscale or how high the point count is. I assumed I needed more subdivisions to prevent the volume from stepping which solved the issue to some degree but took a tool by being a lot heavier in the scene, but I still can't get the thin lines like in the preview. Can someone explain their approach on how they would use POP's and lines to create such result as the picture shows, or just clarify that it is indeed a necessity to push the pointcount quite high and reduce the pscale in volumerasterize as low as my hardware allows. Thanks, C
  20. Hello, I'm trying to implement an OpenCL node that loops over "scatter1" node's points and changes density at the volume A's nearest voxel of every point. However, I can't figure out how to calculate the nearest voxel's index value. So I'd like to know how to calculate the voxel's index value. Also, in the "merge1" node, there is one point added by the volume A(Points count is increased by one after merging). Is there a way to exclude that point when looping over points? I attached my node setup and "opencl1" node's bindings setup below. Thank you.
  21. volume of an object affect on your effect

    hey guys , how can I calculate the volume of an object in VEX , I want to write something like this one below: the line of your script * volume of a specific object I used getbbox_size but the result is a scalar. I want everything in the object to have the effect. what should I do? best regards
  22. Volume shaping in dop network

    Hi guys! Recently I was asking for some advice on how to deform spherical parts of volume into different shapes (in my case skulls). And here is the best reply I've got: "You need a dop I/O node - target your dop network and then point it to your smoke object. Add an import field with the little plus button and import the field named "Pressure". This value is very small but if you use volume visualize nodes or volume vops you can fit the values to pull out the pressure range where these mushroom shapes occur. Once you know the range (usually somewhere around 0.02 to 0.00 for these shapes) you now have the correct mask range. You can now set "Pressure" as the control field in your disturbance tab on the pyro solver. Just make sure you use the correct range, then you can dial the strength of your disturbance applied in only the areas highlighted previously in your volume visualizer. One thing to note - if you want to identify them each you're going to need a sop solver. Once you have the pressure field isolated, you can convert the vdb to poly and use connectivity to seperate them out and then pack them to get a centroid for the specific mushroom. But you're going to want to blend the point position of that centroid over time as it may jitter or pop in and out of existence depending on the tightness of your isolation range. Once those points have a history they'll have velocity and direction you can use to orient your custom field that warps it into a skull or whatever." However, I'm stuck on the last step where I have to setup sop solver and feed the output back in a sim. I would be very grateful for any advice or more detailed instructions on how to set the last part up P.S. I've attached a basic setup file in case if needed sklsmk_test.hipnc geo_02.0001.bgeo.sc
  23. There's vel volume, but I can't see it with vdb analysis. Why not...? help me!
  24. Pyro, not working in Redshift

    Hello I am trying to render a pyro simulation in Redshift. I created a volume material in RS and applied to my Pyro import in Houdini.However I've got a message saying "Failed to find volume file. The file will be empty." I am not sure what I am doing wrong as I watched every possible tutorial about it and the steps seem to be correct. Can anyone help me figuring out what is wrong? I am uploading the file for reference. Many Thanks D Candle_03_Test.hiplc
  25. forces on particles with goal

    Hello! I am still very much getting acquainted with Houdini, but every time I need to use it I have a very specific purpose. This one has me stumped for now, but I am sure that someone versed in Houdini dynamics will resolve it very quickly! What I want to do is: fill a volume with spheres, make said spheres bounce off of each other on contact (like snooker balls), but also try and accommodate themselves onto the original shape (created by the volume). I have tried this with grains, but didn´t get too far. I am betting on doing it with particles: This path seems a lot more promising! I can get the ball´s pscale and id attributes, which will be a boon later on, when I need to swap the balls for different emojis (yes, it´s for a TV ad!). What I need to do: duplicate the current particle so I can use it as a "goal shape", with the same ids. This I can do. add an initial offset to the particles from the surface, ideally from the normals of the original geometry (or a smoothed copy). I can somewhat get it by tweaking the iso offset of the vdbtospheres node, but I worry that the IDs will be messed up. Ideally, I would add an offset to them, but not add any velocity. add a small amount of turbulence to the particles. This will eventually be animated to 0. make them collide with each other, based on their sphere geometry. The eventual geometry is basically spheres as well. make them try and reach their goal, and eventually settle down (a slider for this would be great!) Seems very achievable, but I need some light on how to make these connections! After that, I still will need to swap the spheres for 4 different groups of geometries, but I believe that I can glean information from tokeru.com (Emit_packed_prims_into_RBD_sim), and make it happen. Any help with this will be GREATLY appreciated! This is the scene file: C03_008_DVA.hip (if anyone is interested in taking a look at it!) cheers, Diego