how to stitch two mesh closed mesh A and closed Mesh B

[JihoKang24]

Hi devs,
I have a problem when stitching a closed Mesh A and a closed Mesh B.
I merged the two meshes and unified close vertices (distance 0.0) to stitch the meshes together.
However, after merging, I got an unwanted overlapping (collision) area like this (red area).

Mesh A

Mesh B

Result Mesh

I want to delete or remove this overlapping (colliding) area (the red part).

I tried using thickenMesh(mesh, 0); to remove it, but it changed the vertices of the mesh, which is not what I want.

How can I properly remove this thin overlapping area without modifying the rest of the mesh?

always appreciate for your helps

[Grantim]

Hello!

1. You can use

   MeshLib/source/MRMesh/MROverlappingTris.h

   Lines 21 to 22 in d145d95

   	/// finds all triangles that have oppositely oriented close triangle in the mesh
   	[[nodiscard]] MRMESH_API Expected<FaceBitSet> findOverlappingTris( const MeshPart & mp, const FindOverlappingSettings & settings );

   to find overlapping faces and mesh.deleteFaces to remove them
2. You can use

   MeshLib/source/MRMesh/MRMeshCollide.h

   Lines 38 to 41 in d145d95

   	/// the same \ref findSelfCollidingTriangles but returns the union of all self-intersecting faces
   	[[nodiscard]] MRMESH_API Expected<FaceBitSet> findSelfCollidingTrianglesBS( const MeshPart & mp, ProgressCallback cb = {},
   	const Face2RegionMap* regionMap = nullptr, ///< if regionMap is provided then only self-intersections within a region are returned
   	bool touchIsIntersection = false ); ///< if true then treat touching faces as self-intersections too

   (touchIsIntersection = true) to find overlapping faces and mesh.deleteFaces to remove them
3. I suggest the best way is do detect this faces before merging two meshes, or avoid building them (it looks like these faces are side effect of some cutting algorithm)

Also, it seems that uniteCloseVertices will not work it this case, so you will need to use

MeshLib/source/MRMesh/MRMeshFillHole.h

Line 108 in d145d95

MRMESH_API void buildCylinderBetweenTwoHoles( Mesh & mesh, EdgeId a, EdgeId b, const StitchHolesParams& params = {} );

here

[JihoKang24]

Currently, I'm using the following code to fix edges connected to multiple faces and then remove overlapping mesh faces. However, after this process, border edges appear that seem to have no associated faces. I'd like to know how to remove these border edges
`

fixMultipleEdges(mesh);

auto removeFaces = *findOverlappingTris(mesh, {});
mesh.deleteFaces(removeFaces);

// after deleteFaces fill small holes
{
	FillHoleNicelySettings fillHoleSettings;
	{
		fillHoleSettings.triangulateOnly = false;
		fillHoleSettings.triangulateParams.metric = getComplexStitchMetric(mesh);
	}

	for (auto e : mesh.topology.findHoleRepresentiveEdges())
	{
		if (mesh.holePerimiter(e) < 1)
		{
			fillHole(mesh, e, {});
		}
	}

	FaceBitSet fsLargest = MeshComponents::getLargestComponent(mesh);
	mesh = MeshPart(mesh, &fsLargest).mesh;
}

mesh.invalidateCaches();

`

how to remove this edge (inside black circle)
thank you for your helps !!

[JihoKang24]

After calling fixMultipleEdges once more and then selecting 'Holes' in MeshHealer followed by performing a repair, I observed that the unwanted edges were removed. It would be helpful to know how to replicate this behavior using C++ code.

always appreciate for your helps thank you!!

[Grantim]

Hello!
Repair with this settings just fills small holes.
Could you please share your files so we would be able to suggest you anything (you can share files on support@meshinspector.com if you don't want to upload them publicly)

---

P.S.
In your code sample you actually do not use fill hole settings

	FillHoleNicelySettings fillHoleSettings; // not used
	{
		fillHoleSettings.triangulateOnly = false;
		fillHoleSettings.triangulateParams.metric = getComplexStitchMetric(mesh);
	}

Also, this code do nothing:

	FaceBitSet fsLargest = MeshComponents::getLargestComponent(mesh);
	mesh = MeshPart(mesh, &fsLargest).mesh; // do nothing

If you want to keep only largest component you should do it like this:

	FaceBitSet fsLargest = MeshComponents::getLargestComponent(mesh);
        mesh.deleteFaces( mesh.topology.getValidFaces() - fsLargest );