Making 3D prints of topography on Mars. So far printed: Gale Crater using FDM and Olympus Mons using an Objet.
Next print: Valles Marineris using FDM
To make these, I took grayscale heightmap images using Mars MOLA data, imported the image to a program called Blender, transformed the heightmap into a surface, then extruded the surface down and flattened the bottom.
Next step was converting the models to a .stl file for printing.
After that, I used Netfabb to heal the models and make sure they were printable. To ease the processing load on the CPU, I used the same program to reduce the number of triangles (an stl file means the model is converted into a matrix of many triangles).
The initial number of triangles was upwards of 300,000. After editing and healing, that number was reduced to about 20,000 with little loss of detail.
After that, upload it to a printer, set up the machine, and hit print.