Make a hollow Minecraft build solid I have an .STL file of a Minecraft building which I would like to 3D print. The building itself is &quot;hollow&quot;, but I understand that in the world of 3D rendering, there is no such concept - just vertices and edges.
So the issue I'm having in Blender is that the building is made of units of blocks which themselves are solid, but together create an overall model which is hollow. Thus when attempting a 3D print, the hollow inside of the building is not being infilled which is causing problems.
I just care about the exterior of the model. How do I edit the model in Blender to in essence &quot;fill&quot; the interior of the model? I thought of trying to select all the exterior vertices, then invert, then delete the interior vertices, but that did not work in my case and is unreliable/tedious. I assume there is a proper way to do this anyway (I am relatively new to Blender).
Edit: (Link to file): https://pasteall.org/blend/510d7027732e4e07be713198e682c060
Photos:


The first image is the exterior, the second is the hollow interior. I just want to print the exterior shape as if the whole model were totally solid. How can I achieve this. Thanks!
For 3D Printing, what you need is a &quot;watertight&quot; or &quot;manifold&quot; model. Both terms mean that there are no holes in the exterior of the geometry, but more importantly, no internal faces, which is what you have here.
A great addon for checking your model is the 3D Print Toolbox, which comes standard in Blender, you just need to turn it on!
The simplest way to fix this is to use a Remesh modifier, this will recalculate the object into &quot;voxels&quot; (3D cubes) of a specific size that you can define based on the exterior. This, however, is VERY CPU heavy! It's REALLY slow to calculate!
There is a MUCH better remesh option though. It lives either in the tools panel in the sculpting mode, or under the Remesh tab in the Object Data Properties tab.

0.1mm setting is more than good enough for 3D Printing. But be warned, this is still quite CPU intensive!
For your model, you may need to leave it for a few hours depending on how powerful your PC is!