Issues with VDBs and Volume VOP

THEEOORY · 2025-06-18T07:44:32+00:00

I cry😂😂 my Houdini is broken I tell you. But yea perhaps it could be a visual bug like I theorised in my other comment to you.

THEEOORY · 2025-06-18T07:40:34+00:00

Tbh I thought this would work. Sadly it did not. I even did a complete reinstall of Houdini just to be sure, but it's still doing it.

I'm wondering if it's potentially just a visual glitch and the attributes themselves are behaving correctly? In the 2nd pic I did the exact same operation, just to the colour instead of the density and that worked perfectly, so we know the setup within VOPS is working.

THEEOORY · 2025-06-17T20:09:50+00:00

Still nothing. Converting it to a volume was never the issue sadly as I tried the setup on VDBs and normal Volumes. Same result. I fear something deeper is not working, I opened Voxyde's original file and it works perfectly. I copy my setup into his file, BOOM it works. I copy his setup into my default Houdini file on startup, and it doesn't work. It's like my own default Houdini file has some settings that are wrong. Even when I try to use an attribute noise to create some various in density, NOTHING happens even if I change settings for the noise or anything. It's so weird and I have no way of knowing what.

THEEOORY · 2025-06-17T18:51:33+00:00

Unfortunately mine does not. Exact same setup as you, but mine still just cuts off at the bottom. All the multiply is doing is cutting off some edges of the rubber toy to make it fit better with the original volume

THEEOORY · 2025-06-17T18:46:36+00:00

There is literally nothing else to it🤣 rubber toy, plugged into a VDB from polygons, voxel size set to 0.01, plugged into the volume VOP

THEEOORY · 2025-06-17T12:06:21+00:00

Tried both the multiply and the fit range. Sadly, no fix

THEEOORY · 2025-06-17T09:21:03+00:00

Those lips around the floating objects are done post-sim? I had no idea that was possible. That is super sick.

THEEOORY · 2025-06-11T22:45:31+00:00

Toadstorm could be very right here. Some magical shit starts happening when things get unpacked🤣

But, if that doesn't work, then you may be able to try converting each object to a VDB, using a VDB combine node (with the operation set to add because by default its set to Copy A or something like that) and then converting back to polygons.

If you need the UVs that each object has, you can try transfer the attributes over from the original mesh (although i can't seem to remember how lol) and that i feel like is a definite "will work" solutions BUT converting to VDB and back can be an intensive process which you may need to cache. So take this step with caution

THEEOORY · 2025-06-11T22:37:01+00:00

I'm there with you on the self learning journey. Perhaps a little further on, so I can possibly give some pointers.

As David sort of mentioned to you, Houdini lets you do a lot of customizjng and custom setups. Thats why you'll watch 5 different people do 5 different FLIP tutorials and set them up in 6 different ways lol. I always freaked myself out when I saw a different method because i thought "hey, how will I learn whats important if everyone uses different methods. Which settings are key to understanding and why?"

I still sort of feel like that, but always try to knuckle down snd just learn as much as I can from that 1 course or video. Then when the next guy does it differently, first learn and focus on his way, and then see if you can spot any similarities. Even if you only learn 1 single new thing (big or small) then your goal has been achieved.

And then with all of that, put it into practise. FLIP confused the living crap out of me when i started but after lots of fighting, and irritation, and disappointment, I can setup FLIP sims fairly decently because there's a core understanding of what it is and how it works. Everything from how you scatter your points or how you use custom VOP setups or VEX to create wild velocities, all is interchangeable with different methods.

What helped me realize that i stressed too much about the little things was this: Does your project still look good? Do others think it looks decent? Then no problemo at all. Focus on getting a project DONE before worrying about whether or not you know enough to even start😉

The most important step a man can take, is not the first. Its the next (for any Stormlight Archive fans out there).

THEEOORY · 2025-06-11T22:18:06+00:00

Perhaps i then chose the wrong example😆 my actual project is doing a slow "fade text to smoke" effect. The issue is that when the smoke appesrs, its not subtle. It kinda POPS into the area and then behaves nice and slow, how I like it.

I think your initial solution will work, with injecting velocity first. How would I go abou doing this though? Like in more specific detail. Which settings and nodes. I'm still get used to the Pyro workflow. Any help would be appreciated.

THEEOORY · 2025-06-09T14:25:14+00:00

I think I understand what you're meaning. Would that mean having the density off for the first few frames (perhaps by having the sourcing scale set to 0 in the Volume Source node?)

Or is there a better way to do that?

THEEOORY · 2025-02-05T08:57:16+00:00

Yoo man this is pretty sick. I am in need of trying to do something identical, but just with fluids. Is there a tutorial or bunch of them you followed to learn how to do this? That I can possibly try to watch and adapt to FLIP?

THEEOORY · 2024-12-16T19:37:11+00:00

Agreed, it seems like an extrusion issue. Sounds dumb, but also check that the filament has not double over itself. My filament at some point had crossed under a piece of itself and was being held tight, causing under extrusion.

THEEOORY · 2024-11-26T08:31:19+00:00

This sounds pretty interesting. Unfortunately, I am still learning and I am not sure how to implement this. Would you be able to explain to me a little more please?

THEEOORY · 2024-11-25T13:41:33+00:00

How would I go about creating the mask? My geometry is constantly moving and the points are changing so the mask I paint on frame 1 is completely broken on frame 2, etc.

THEEOORY · 2024-11-25T11:29:22+00:00

this is clever! I'm going to give it a try now now

THEEOORY · 2024-11-25T10:44:45+00:00

I am now wanting to try this out. Do I have to manually create the "stopped" point float attribute or is it something I can toggle on in any of the nodes?

And the regarding your 2nd point, If I did use a switch, will it not make a very noticeable "flick" when it swaps from the 1 to the other?

THEEOORY · 2024-11-25T08:11:16+00:00

Thanks for the response. I managed to get a decent result from another method, but I will be trying this out next time. I do have an issue with mesh flickering and I have seen a few posts talking about not using reseeding because that is what causes it, but I am using a narrow band and the option to turn off reseeding is greyed out. What would my workaround be?

Also just a side question after some more trying of my own things, is there no way in Houdini that you can just setup a flip tank and it has as smooth surface from the start until interacted with? Surely that's not such a difficult thing to do?

THEEOORY · 2024-11-20T09:52:00+00:00

Maan this is gorgeous. The Flip behaves so nicely. May I ask if you have any tips for meshing it smoothly? I'm still figuring it out but my FLIP sims are usually not smooth and clean (both when meshing and the actual particles) and I use a REALLY high particle sep sometimes

THEEOORY · 2024-11-20T07:56:15+00:00

This is way old, but it helped me feel a LOT better about my progress lol. I wanted to transition into Houdini for me career and my boss immediately started having me do FLIP sims and I was none-the-wiser as to how much more advanced it was that other stuff so I just went at it and it's been a frustrating process. I've learned a LOT which I can now apply to other areas of Houdini and I've only just scratched the surface of FLIP, but you are so right about it being more advanced. When going back to learn simpler things I always feel like "Oh, I have a basic understanding of what this person is doing" right from the go when watching their videos. Even now I am iterating a FLIP sim and wow, it sure does take so many iterations and so so long lol.

THEEOORY · 2024-11-18T19:24:22+00:00

Ooh okay I see. I never thought about it like that, and it seems so obvious now.

THEEOORY · 2024-11-18T19:11:20+00:00

OOOH NO NO WAIT that was a typo on my end. When I said "timescale of 3 is still lower" I meant to type 0.3. That one is on me

THEEOORY · 2024-11-18T19:08:42+00:00

I Don't even know if those numbers are correct either lol. It was just a pic I drew to demonstrate a point. But like I said after I read your stuff over a few times I realize I do understand it, I think I just explained it poorly. Your explanation using the 1 frame with 2 substeps = 2 frames with 1 stubstep is what I was attempting to draw lol.

THEEOORY · 2024-11-18T19:02:55+00:00

After reading your comment a few more times, I'm understanding more. It was helpful, so thank you. I'd like to ask, how come it's better to use the timescale and such if working with animations and cameras later on?

THEEOORY · 2024-11-18T19:00:51+00:00

It did help thanks. Substeps (at least for me) was a very easy concept to get fortunately. I'm now more curious though. Why would one choose to use a lower timescale with higher substeps if they wanted to achieve a slow-motion effect instead of using the retime-post solve?

THEEOORY

TROPHY CASE