Mineways is a free, open-source program for exporting Minecraft models for 3D printing or rendering. With this program, you can easily upload and view (for free) and buy models using 3D print services. You interactively select a model from a world map, which creates a 3D print file. You have the ability to preview this file with MeshLab or other 3D file viewer. Then, you can send it to your own 3D printer or a 3D printing service to make the model real.
