I have made a terrain 3d model in Rhino. The model should be fine, no bad geometry, no open polylines, no naked egdes or non-manifold. I then select it all and try to turn the nurbs to a mesh but i only get a square. I have tried tuning on the advance settings but it doesnt seem to make any difference.

Please help me, the file is to be 3D printed as a landscape model for my master thesis, and it is driving me insane, let alone takes up too much of my time


the file is this (amongst several) A.zip