Regarding Mesh Format .vol

Thanks for your reply but I am still slightly confused about what is the difference between surfnr1, surfnr2 and surfid. All of them are somehow related to the surface ID to which this edge is connected. From my understanding, surfnr1 and surfnr2 are the ID of the surfaces which share this edge. Then what does surfid signify?

Hi,
When I type mesh.Export(name,file) in my code, It just showed up this message (AttributeError: 'ngsolve.comp.Mesh' object has no attribute 'Export').
And also where will the export file be saved. Thank you

Hi, there is a difference between the ngsolve mesh (a fem interface to the netgen mesh) and the netgen mesh itself. The export function is defined for the netgen mesh. You tried to call it on the ngsolve one. You can get the netgen mesh by calling mesh.ngmesh. The file is saved relative to your current path.
Best
Christopher