[abenedik]

You can use Ab3d.Utilities.MeshUtils.CombineMeshes method and pass all the meshes to the method. This will just add the positions and triangles to the final mesh without any additional logic.

The MeshBooleanOperations.Union can also use the CombineMeshes method when the specified meshes do not intersect. But when they intersect, then a standard Boolean Union operation is performed - this can create many additional 3D positions because Constructive solid geometry is used for that operation.