VDB From Polygons , HOLES IN VDB

[quentin]

Hi everyone,

I've an issue with vdb and i can"t find a way to solve this (so that's why i'm here haha)

 

I'm working on a fluid simulation and i need to get the mesh into vdb to use it as collision surface.

I'm trying to get a polygon mesh into vdb with the node vdb from polygone but there is holes and artefacts..

the issue is when i'm converting polygons into vdb with vdb from polygons there is a lot of holes into the vdb and I can't use it for my sim ( the particles goes through it).

 

 

I think the problem comes from the mesh but I can't find what it is. (the mesh comes from Zbrush)

I tried with a collision source node, same result as vdb from polygons.

I can't find a way to get a clean vdb fron this mesh.

 

 

So I wonder where those holes coming from and how can I fix it ?

If someone have the solution, that will be great =D 

thanks a lot !

 

 

 

 

Edited August 25, 2021 by quentin

[Atom]

There may be holes in your polygon mesh, or non-fused points. Try dropping down a polyfill and choose single polygon fill mode before your vdbfrompolygons. After that, if you still have holes, you may need to reduce voxel size on the vdbfrompolygons until they disappear. For a shape like you have shown in your reference, I might be tempted to construct a low poly proxy mesh to serve as the collision object.

The higher resolution you need for collision, means the higher resolution you will have to push the fluid simulation. This can increases the simulation time. It's worth the effort to simplify your collider unless the shot specifically requires an up-close interaction with the "hero" collision object.

Edited August 25, 2021 by Atom

[paranoidx]

There is a way I have just learned. You can scatter points on your mesh then convert to VDB collision which could produce faster workflow in some case rather than go and fix every meshes you had.

[quentin]

SOLVED !

 

Thanks for your advices and ideas Grand Master.

I tried your way too Paranoidx and it works fine, it's a very powefull way for remeshing !

 

I Still wonder why voxels are so wierd...

 

Thank you Guys !

 

 

 

Edited August 27, 2021 by quentin

[Fenolis]

The problem occurs because parts of the mesh are thinner than the voxel size specified during conversion. This results in the creation of voxels that are not "full" and thus allow other voxels like fluids to leak through them. The solution to this kind of leaky problem is to reduce voxel size during conversion (to more accurately represent the bounds of the geometry), matching the voxel size of the fluid sim to the voxel size of the geometry (or have the fluid voxels be smaller, so they don't penetrate the thicker boundaries), or use thickened/solidified proxy geometry.

[quentin]

Hi Fenolis, thank your for your explanation, I understand the cause of my problem now.