Adding thickness to a terrain 3D surface


I have a good quality 3D model of a surface, in obj format. I would like to 3D print it, so I need to add thickness to it. I would like to be able to put the model on a table, so I hope to be able to “attach” my surface on a flat bottom, with flat walls. Like a section cut of a mountain.

I thought I could create a cube, and “intersect” the 3D surface with a cube…but I am not sure where to start. I am a beginner, so the question may sound stupid…

I know that I will have to make the cube hollow to decrease cost afterwards…




Select the all the vertices around the edge of your model and E to extrude them downwards. Scale them along the z axis by zero (S / Z / 0) to make them flat, then fill the bottom with a face (F)

I am glad I asked…I just tried on a very small volume I built, and it works great. Now…any idea how to select the vertices around my complex model? Do I need to do it manually, or is there a shortcut? The line is basically the orange line I see when I select the entire object in object mode, but I wonder if there is a way to select it easily in select mode?


Select all, menu Select - Boundary Loop.