Fluid particles fall through scanned mesh.

[RobH22]

I know this sounds basic but I can't find any posts here that talk about it. I had a photogrammetry mesh that is a convex shape. I want to fill it with particles. No matter what I do, they pass through it.

I've remeshed and repaired it so many times it's not a scanned mesh anymore and I've lost the texture. That's OK, I just want to fill it with water. The normals are correctly oriented, the mesh isn't excluded, I've added 'Edit Polys' and flattened it. I've optimized and remeshed it. I've put a shell on it. Nothing prevents the particles from passing. I put a simple plane below and it stops the particles so I know things are working.

What am I missing?

[ambrozie_pura]

A "Shell" modifier should fix the issue.

[RobH22]

It does not. You might have missed that I mentioned I'd tried that. I tried it several times at sometimes extreme thicknesses. I keep thinking there is some parameter I've accidentally turned off or am missing.

[ambrozie_pura]

I only looked at the screen grab. Have you tried making the shell really thick? Also collapse the modifiers.

[tobiasroesli]

Phoenix needs some thickness of the geometrie to work proper... I don't know max but phoenix is in that case the same like Maya I guess. And your Substeps are very low. It could be that you get problems with the sim then.
I don't know what shell modifier does but it doesnt look like it makes a thickness or extrusion which you sould have for Phoenix...

Cheers

[RobH22]

Yes, I made it ridiculously thick a few times of different amounts. No luck.

Let me try the substeps. I think I may have overlooked that. Which section are you looking at when you say 'substeps' so I'm seeing the same ones as you are talking about.

[tobiasroesli]

substeps per frame, increase it to 4-8 steps or even higher for final sim. It depends on how fast your emission is and in your case how close it is to the collider.

[RobH22]

I can't find 'substeps', I can only find 'Steps Per Frame.' Is that what you are referring to or is 'substeps' somewhere else and I'm not seeing it? I wish Max had a parameter "search" feature like Unreal Engine.

I attached a couple of grabs. One shows a shell with 'NO' errors and the other shows the particles just falling through with '20 steps per frame.' This is so basic it's silly, but it's evading me.

[RobH22]

This is something I'm just playing with and not a real project. So, 'workarounds,' while OK, are not my goal. My goal is to figure out why the one mesh is completely unaffected by Phoenix particles no matter what I do. I'd really like to figure it out to learn somehting valuable for future projects that might suffer the same problem.

However, I exported the mesh to Rhino and did a 'Quad Remesh' and brought it back as an FBX. It now stops the particles. While a viable solution, it still leaves me scratching my head as to what data in the original mesh prevents it from deflecting particles. I may never know.

Thanks for all the help and comments. I appreciate it.

[tobiasroesli]

Yeah, thats what I meant... strange behaviour. I dont know. Something is wrong with the geo, does it work with a simple grid or cube? Maybe holes in the geo or double faces or something like that.

[RobH22]

Thanks Tobias. Yes, really odd. No holes, no double faces. no errors with an 'STL Check.' Simple planes and cubes work fine. I exported it out as an FBX and reimported it. Didn't work. None of the Max repairing, remeshing or other tools would correct the error. Only by exporting to Rhino, doing a 'Quad Remesh' and reimporting that was I able to get it to repel the particles. Very odd but intriguing. I'll keep experimenting. I want to know what broke this original photogrammetry mesh.

[Joelaff]

Max Retopology modifier didn’t fix it? Maybe weld modifier first…?? Weird.

[RobH22]

Nope, I used 'weld' early on. I deleted isolated verts, I created a manifold mesh. Not my first rodeo. The only thing that would fix it was to take it out of Max and have another program (Rhino this time) rewrite the file format. I used FBX. None of Max's tools would correct whatever was corrupt in the mesh data. It was strange for sure. Sometimes you get an odd one like this.

I just wanted to make sure I hadn't overlooked some parameter or something.

[Joelaff]

All I can think is perhaps the shell damaged the mesh (caused it to overlap or get degenerate faces), but I see you have an STL check after the shell as well. So who knows. I absolutely hate this sort of geo issue. Drives me nuts.

[georgi.zhekov]

Sounds really strange - can you send over the scene with the not working mesh, maybe we can debug it on our side?

You can send over the scene through support.chaos.com (submit a request at the top right) or attach the scene here as a zip file.

Thanks!