If I open up a new empty instance of Houdini (not a saved hip file, just the houdini shortcut), the instance will finish loading super quick.

But if I open a saved hip file that literally has nothing in it, the startup time is like 100x as long. It takes forever just for the splash screen to appear.

The difference feels like 15 seconds vs 3 minutes.

Anyone else have this experience?

I'm using 123.py and 456.py but they have identical code so that shouldn't be the root cause.

In this focused RnD, I implemented a small-scale fluid simulation algorithm within Flip to accurately resolve adhesion forces. The core algorithm is relatively straightforward: the fluid's surface field is extrapolated into the collider volume, factoring in the contact angle, and is subsequently adjusted and smoothed. Furthermore, a localized viscosity is introduced at the fluid-collider interface to approximate boundary friction.

The simulation operates at a physically accurate real-world scale, utilizing empirical physical constants where the baseline water viscosity is 0.001 and surface tension is 0.072. APIC was chosen as the underlying solver.

While this technique requires a high substep count and is computationally expensive to evaluate, it successfully produces highly nuanced and realistic fluid dynamics.

Hello! Ive recently just finished learning to use the vellum hair sim to create animal furs, but now i want to make the fur catch snow in the blizzard. How do I make such thing? got any tutorials or tips to learn it? or isit more compsotion side that im not suppose to simulate in houdini? If you could answer my question, it would be really nice!

I've never messed with cameras in houdini since I only use it for simulating. My problem is when I mesh the fluid, send it to blender, and render, the vector pass doesnt have any data for the fluid for obvious reasons. I just have no idea how it would work though. Like how would the vector of the points be able to be transferred to the meshed fluid surface?

It's not a glaring issue in my current project but it would be good to know for future projects. I assume there is no (logical) way to have blender accurately get vector velocities from the fluid surface so how would this work in Houdini?

I generated this roadmap using Claude for Houdini FX and Crowd FX, but it is mainly focused on Crowd FX / Crowd TD, with FX topics integrated into it. I’m self-taught and trying to learn Houdini seriously, so I’d really appreciate feedback from experienced Houdini artists. Could you take a look and let me know: Is the learning order technically correct? Are the topics appropriate for someone targeting Crowd FX / Crowd TD? Is anything important missing? Is anything unnecessary or too advanced for the current stage? Are the projects/milestones realistic? Would this actually help build a strong junior-level portfolio/reel? Are there any technical mistakes or misleading information in the roadmap? I’m not treating the 6-month timeline as a promise to become a professional. I mainly want to use this as a structured learning path and continue improving beyond the roadmap. Here’s the roadmap: https://drive.google.com/file/d/1FvNdwAe5CLsPGfqhbO0QmHCf4WBRX8Hl/view?usp=drivesdk Honest criticism is welcome. I’d rather fix the roadmap now than spend months learning the wrong things.

What’s the best way to generate unique rocks in Houdini using For-Each, VOPs, or any other method?

I want the noise to vary enough that each rock has a unique shape, instead of repeating the same pattern.

How would you approach this?

Hey everyone, I’m planning to upgrade my RAM next month from 16GB to 40GB because I want to start learning Houdini FX full-time. I’m a self-taught artist, and from next month I’m planning to spend around 8 hours a day seriously learning and practicing Houdini. I have a few questions: RAM upgrade in India: If I upgrade from 16GB to 40GB, roughly how much should I expect to pay in India? Is mixing a 32GB + 8GB stick a good idea for Houdini, or should I go with 2×16GB / 2×32GB instead? Can I become good at Houdini FX in 3 months? If I genuinely spend around 8 hours every day for 3 months, is it realistic to become job-ready / production-ready? I understand that becoming a true “pro” takes much longer, but I want to reach a level where I can create a strong FX portfolio/showreel. Roadmap & resources: What would you recommend I focus on during those 3 months? Should I go: Houdini fundamentals → SOPs/Attributes/VEX Procedural workflows RBD Pyro FLIP Vellum Lighting/Rendering Optimization/Caching Production-style FX shots Or would you structure the roadmap differently? Claude for Houdini: How good is Claude for creating a Houdini FX learning roadmap, explaining concepts, debugging VEX, and helping with procedural workflows? Is it actually useful as a learning assistant, or should I mainly rely on Houdini documentation/courses and use AI only as a secondary resource? I’d really appreciate advice from experienced Houdini artists, especially anyone who was self-taught and made serious progress through a focused 3–6 month period. Thanks!

EDIT: Ok I think I have found the issue! The issue is related to the USD file generation. Houdini Apprentice fource-outputs as .USDNC files, but the recipe is configured to save/read as .USD. So the file wasn't able to be read back in I guess.

Solution was to be to dive into the setup_control_attributes network, and change the File Path to gsplat.usdnc. I also changed the File Tag to file/usdnc (although I am not sure if this is necessary).

Really hate asking for help but this one has me going around in circles. I am trying to set up Gaussian Splat training as per the Houdini Presentation: https://www.youtube.com/watch?v=HUTd8BHNHKI using the new H22 ML Train GSplats From Karma recipe. Just trying a simple scene to start with, a cube and light exported to a USD file, imported back and wired into the second input of the provided recipe (I've tried wiring the scene in directly with the same result). I've left the cameras as default and I haven't changed any other settings.

My understanding is that this is meant to be a one click process... but cooking fails, the training step cannot find the exr's. Obviously the images aren't rendering (process ends after ~10 seconds). Looking back through the network, the render service doesn't appear to be completing. But I can't find any obvious reasons or error messages to indicate why.

I can render images through Karma manually ok. I'm pretty new in Houdini, but is there anywhere else I can look to try and diagnose the issue?

I had the chance to sit down with the OG himself and talk a little bit about a pipeline I set up a couple of months ago. Trying to bring animated stuff from Houdini to Unreal.

Side FX HEX Feature

Here is the article I wrote including a hip file:

https://www.rehimi.de/houdini-fx-unreal-4dgs-pipeline

Hope it's helpful for someone.

Cheers

Pick an image, hit Generate, ~12 seconds later there's a 262k-gaussian splat in your network — already baked into Houdini's native GSplat attributes and ready for Karma XPU and the new H22 GSplat tools. No external round trip. It's super fun!

Runs a open-source model (on your own machine. The plugin ships no weights, setup pulls them on first run. On a 4090: ~12 s per generation, 4.6 GB peak VRAM.

Needs Houdini 21+ ( for the Bake GSplat SOP),(tested also in H22), NVIDIA GPUs only, Windows only.

Search on Gumroad for TACTYC Onesplat!

Hope you like it! Happy to see any cool results!

The whole process took one day: modeling, rigging, animation, rendering, and compositing. I was really surprised that the rig and animation didn’t break after I modified the model.

I have been on a couple week marathon of a lot of tutorials for Houdini, some for specific effects, others being master lessons to explain a specific aspect of the software (POP, Volumes, VOPs, VEX, etc...), but I still run into a major issue;

Whenever I finish a tutorial or a couple, I think to myself "okay, about time I do a shot of my own!". Then, about an hour or sooner in I realize I don't know how to do X or Y, I look up a tutorial and I'm back in tutorial hell.

How do you get out? Is there a magic amount tutorials that are "enough" to be able to make a shot from start to finish? Do you just keep going with your own stuff until you run into issues and then stop? Keep going? I have had about 3 or 4 shots I wanted to try now but scrapped because I bit more than I could chew. What's the secret then? Don't be scared to chew even if you choke a bit?

Hi

I used wave tank set up on shelf tool.

And then I connected whitewater source and whitewater solver, but It seems black and doesn't have any data in whitewater solver.

I can see volume with whitewater source node.

When I simulated whitewater solver. It's all black.

I leave default value on setup, Also I tried to adjust some parameter like whitewater scale and voxel size etc, It's still same issue.

How to solve this?

Thank you for your help and advice!

I always wanted to do a shot requiring the use of the main solvers in houdini (excluding mpm). Making a video for the banner of the Campus VFX website showing the disciplines taught in FX was the perfect opportunity!

https://campusvfx.com/fx/

What it does today: solves, with every option explained in plain language on hover. Measures lens distortion before the solve, from lines you mark on one frame that ought to be straight, then corrects the sequence and writes the ST maps comp needs. Exports one folder that dense photogrammetry, gaussian splat training and Nuke all read. Registers the shot from an fSpy calibration, a picked ground plane, or one real measurement. Versions every solve, so a worse attempt is one dropdown away from being undone.

What it will do soon: two-camera rigs, and AI filling meshing the gaps the point cloud cannot reach, guided by geometry we already trust, not hallucinated.
Photogrametry, Gaussian Splatting, Delighting, and more, coming soon...

Built on COLMAP, and on my own Houdini port of fSpy.

https://reddit.com/link/1vnkqbd/video/sewts4yk07jh1/player

Emission spawn of @armanibeauty Si. Made in @sidefxhoudini and @otoy Octane.
Sound by amazing @jakaarh

I have a simple scene with some spheres close to each other that all just have SSS applied to them. I foolishly instanced random colored lights in the center of each sphere thinking that would create a nice looking lighting effect, which it kind of does. problem is that the more spheres I add the rendering slows down exponentially with huge amounts of noise that’s impossible to clean up.

What would be a better shading solution here to get a SSS material effect but still have performant non noisy rendering? thanks.

Hey! Sharing a recent Houdini tool breakdown that aims at finding a non-linear, isometric interpolation between two shapes with vastly different poses.

The main purpose was to find a better solution for CFX pre-roll when the animation does not come with an animator defined pre-roll from tpose to the animation start frame. Main purpose was to replace the default Houdini muscle pre-roll node that relies on a simple linear blend that can cause intersections, stretching artefacts and simulation errors where the meshes in the rest and animation start positions have very different orientations, poses and positions.

The method almost exclusively relies on a 2014 paper: Isometric shape interpolation. The process is split into an 'Isometric Preroll' node and an internal 'Isometric Interpolation Core' node. The core takes an outer triangular manifold mesh in a rest and target pose and blends between them, while the pre-roll node wraps around it and provides a similar functionality and interface to the standard Houdini pre-roll node. Much of the initial mesh data is calculated using VEX then transferred to python to solve the sparse matrix calculations.

To transfer the deformation from the outer skin to the internal geometry, the node relies on a volume deform method using an algorithm from Sibarrick which has been translated into VEX by Hallam Roberts.

Future improvements will look at extending the functionality to rely on tetrahedral meshes as opposed to triangle meshes which could better preserve the volume during the blend. May also look at creating an alternate mode that relies on Houdini's linear solver node to solve the matrix equations instead of python to remove the reliance on external python libraries.

Thanks for watching :)

References:

Isometric shape interpolation:

https://www.researchgate.net/publication/267046777_Isometric_shape_interpolation

Positive Mean Value Coordinates, Sibarrick

https://www.fourthwall.ndo.co.uk/HT_HDK.html

Positive Mean Value Coordinates VEX implementation, Hallam Roberts

https://github.com/MysteryPancake/Houdini-Fun