VolumeToMesh generating non-manifold geometry

[Stephen]

Hello,

I'm noticing I frequently get non-manifold edges in meshes generated from VolumeToMesh, even on some of the example vdbs like the bunny and armadillo. Just wondering if this is expected behaviour or a bug in the mesher code? I see a function named isNonManifold in VolumeToMesh.h, so I'm guessing there is at least some level of checking going on, but I admit I haven't really studied this code in-depth.

The pattern I most often see is three quads which share a single edge, like in the pic attached.

[OpenVDB Support]

Hi,

This is unfortunately expected. Dual contouring meshing schemes can generate non-manifold surfaces, this is an inherent side effect of placing one single vertex in each cell. The isNonManifold method is used in the VolumeToMesh scheme to avoid adapting in regions were the grid is non-manifold. Several papers try to deal with this issue and I'm looking forward to investigating this more.

"Dual marching cubes - Nielson, G.M."
"Manifold Dual Contouring - Scott Schaefer, Tao Ju, Joe Warren"
"Dual contouring with topology-preserving simplification using enhanced cell representation - Hong, W.; Kaufman, A."

/Mihai

[Stephen]

Ok, thanks for the info Mihai.