FLIP FLUID: Question about Particle Fluid Surface

[Phiphat]

Hi,

I just started using Houdini recently, and it has been great so far. I was studying the set up from Masterclass ocean tools for Houdini 16 for endless ocean.  After I finished caching particle fluid surface, I noticed that some of the frames weren't meshed correctly. At first I thought it was Voxel Scale so I changed it from 0.75 to 0.6, which fixed some frames, but now it happened to other frames that wasn't happening before. I attached some screenshots of the bad frame(frame 1052), and good frame (frame 1053), and also the folders of current version (v04), and the version before (v03) to show you that they are happening in at different frames. I do not know enough about Houdini to fix this myself, will you kind strangers on the internet help me out?

Thank you so much,

Phiphat Pinyosophon

 

 

Edited October 28, 2017 by Phiphat
adding link to a masterclass that I was following

[evanrudefx]

Because the frames that are "broken" have much smaller file sizes, I would think there is a problem with the file itself you would need to re-cache those specific frames. Have you tried that?

[Phiphat]

Hi ejr32123,

Thank you very much for replying. I have tried that, I also tried to recache those frames with different value, and it still gave me the same problem, just at different frames, as you can see in my screenshot of v03 and v04 caches. It gave me the same result, when I was looking at particle fluid surface node itself as well. I tried turning off "Flattening Geometry" and the problem goes away, but that's not what I wanted to do. 

Best,

Phiphat

[Zybrand]

Hi Phiphat,

Sounds like you narrowed down your problem to the "Flatten Geometry" section of the Particle Fluid Surface. You mention that the problem happens at different frames with different particle separation values but does it consistently happen at the same frames at the same resolution? If so that eliminates any sort of ram limit issue. 

If you dive inside the Particle Fluid Surface you will find a FLATTEN subnet which handles the bounding box and flatten geometry calculations. In there VBDs are being edited and merged together with a VDB combine using SDF difference and another using SDF union. That is most likely with your problem is because it looks like on of those VDBs are being calculated wrong and subtracting the whole fluid surface on those frames. The simplest thing to try first is just to adjust your bounding box size and see if the problem persists. 

[PalTopin]

But if you´re doing it with by hand with VDBs what I do is to downres the voxel separation just to see that work in every frame and then use a VDB resample to have back again the resolution for the convert VDB.

[Phiphat]

Hi Zybrand & PalTopin,

Thank you for replying.

Quote

You mention that the problem happens at different frames with different particle separation values but does it consistently happen at the same frames at the same resolution?

yes, it happened at the same frames at the same resolution. 

I'll try out your solutions and see what happen. Thank you so much!

Phiphat

[Phiphat]

Hey guys,

I got it working!! I changed Rebuild SDF from "Adaptive" to "None". The file sizes came out a bit larger, but I no longer had issue where my ocean disappeared randomly. I tested it out on my old scenes with these issues, and I could cache it out with no problem.

Thanks for all the help, I really appreciated it.

Phiphat

[silkey]

Thanks Zybrand

On ‎10‎/‎30‎/‎2017 at 2:10 PM, Zybrand said:

Hi Phiphat,

Sounds like you narrowed down your problem to the "Flatten Geometry" section of the Particle Fluid Surface. You mention that the problem happens at different frames with different particle separation values but does it consistently happen at the same frames at the same resolution? If so that eliminates any sort of ram limit issue. 

If you dive inside the Particle Fluid Surface you will find a FLATTEN subnet which handles the bounding box and flatten geometry calculations. In there VBDs are being edited and merged together with a VDB combine using SDF difference and another using SDF union. That is most likely with your problem is because it looks like on of those VDBs are being calculated wrong and subtracting the whole fluid surface on those frames. The simplest thing to try first is just to adjust your bounding box size and see if the problem persists. 

Saved me a whole lot of headache.

;p