Marching cubes

Downloading Blender & Installing the SMC Addon

Download Blender (version 2.61):
Win 32: https://download.blender.org/release/Blender2.61/blender-2.61-release-windows32.zip
Win 64: https://download.blender.org/release/Blender2.61/blender-2.61-release-windows64.zip
Others: https://download.blender.org/release/Blender2.61/
SMC Blender addon: https://minhaskamal.github.io/DownGit/#/home?url=https://github.com/wrack/blender-smc-exporter
Move the io_export_smc.py file to the folder blender-2.61-release-(...)/2.61/scripts/addons
Run Blender, go to File > User Preferences > Addons, in the search field in the upper left corner type smc and press enter.
Enable the checkbox of the option "Import-Export: Export Sauerbraten (.smc)" (if it is not visible, go back to step 3)
Click on "Save As Default", now the option to export to .smc should already be available.

Back to the viewport, create your model and make sure to apply the rotation/scale/location (CTRL + A > Rotation & Scale and CTRL + A > Location).
Go to File > Export and click "Sauerbraten (.smc)"
In the bottom left corner you will notice a tab with two options "Grid Power" and "Cube Count", Grid Power defines the size that your model will have ingame, Cube Count is the amount of detail your model will have (I recommend 60/100, but you can enter any value you want, it will affect the export time).
Save the .smc file inside the Sauerbraten root folder (needs to be a modified client with the importsmc command available).

In order to access the importsmc command, it is necessary to have a modified client.

Ingame and in edit mode, select a cube and type /importsmc filename.smc, done.