What does concatenateMesh exactly do?

Hi, I wanted to get some clarification regarding the application of the concatenateMesh feature in the geom3d toolbox. I am trying to achieve the following: 1) Build a tetrahedral mesh to describe a sphere. 2) Build a tetrahedral mesh for a box whose center is coincident with the sphere and the size is ~ 5 times the sphere. 3) Create a single mesh containing both sphere and box. I would like to better understand which is the best way to use concatenateMesh to do this. Option 1: Build the sphere mesh (V1, F1) separately, box mesh (V2, F2) separately. Use [V, F]=concatenateMesh(V1,F1,V2,F2) to achieve my objective. Option 2: Build the sphere mesh (V1, F1) separately, box mesh (V2, F2) separately. From the box mesh reject all nodes and tetra that lie inside the sphere. Smooth box mesh. This is (V3,F3). Now make [V,F]= concatenateMesh(V1,F1,V3,F3) The demo concatenateMesh appears to suggest option 1 will work. However, when I built the script and checked for the volume of the sphere by summing the tetrahedra to the analytic volume, it appears option 2 needs to be deployed. Could you please confirm? The second question I have is, does the concatenateMesh check if all nodes are properly connected in the new tetrahedra or is there something else I need to do to ensure nodal connectivity?

Many thanks for all your help. Thanks, Best wishes, Souvik