Mesh Clean Up

[nsmela]

Hey there,

We are failing boolean operations and suspect one of the meshes isn't manifold. Is there a way to determine where the issue is and to fix it?

[Grantim]

Hello!

Our internal format does not tolerate non-manifold meshes, but there could be self-intersections or incorrectly oriented components that might lead to error in boolean. Also, you could provide meshes to us and we will help you to locate suspicious area.

[nsmela]

Thanks for the offer, but I'd prefer to have a better understanding of the library. I want to eventually use a class to evaluate a geometry to report all defects. Is there an easy way to do that with library?

[Grantim]

I understand. There is no one general function to detect all possible issues, different issues require different checks. For example you can use findSelfCollidingTriangles to detect self-intersections on mesh:

MeshLib/source/MRMesh/MRMeshCollide.h

Lines 33 to 36 in ab8e4ca

	/// finds all pairs of colliding triangles from one mesh or a region
	[[nodiscard]] MRMESH_API Expected<std::vector<FaceFace>> findSelfCollidingTriangles( 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

Or findDisorientedFaces to find faces with suspicious orientation

MeshLib/source/MRMesh/MRMeshFixer.h

Lines 146 to 147 in ab8e4ca

	/// returns all faces that are oriented inconsistently, based on number of ray intersections
	[[nodiscard]] MRMESH_API Expected<FaceBitSet> findDisorientedFaces( const Mesh& mesh, const FindDisorientationParams& params = {} );

Or findRightBoundary to detect holes

MeshLib/source/MRMesh/MRRegionBoundary.h

Lines 27 to 31 in ab8e4ca

	/// returns all region boundary loops;
	/// every loop has region faces on the right, and not-region faces or holes on the left
	[[nodiscard]] MRMESH_API std::vector<EdgeLoop> findRightBoundary( const MeshTopology & topology, const FaceBitSet * region = nullptr );
	[[nodiscard]] inline std::vector<EdgeLoop> findRightBoundary( const MeshTopology & topology, const FaceBitSet & region )
	{ return findRightBoundary( topology, &region ); }

There are more checks for other types for issues, so it seems reasonable to search only for expected ones and not all of them.

[nsmela]

Awesome, thank you

[nsmela]

Those functions are not exposed to c sharp yet, I'll add them to my TODO list for you guys. In the meantime, I've checked the mesh out in blender and couldn't find any defects.

EDIT: Found the issue. I wasn't updating the output when it failed, so I'd only see the mesh if it was good. The mesh does self-intersect. Uploaded stl was removed to avoid confusion.