Well first of all you will need a few programs to make this work, but once you have everything its a pretty easy process to make quick and easy terrain in Hammer.
- Terragen - Download
- Yes, there is a licensed version and a free version. The free version has some restrictions, but will work fine for what you will be using it for.
- TGPGuiLib - Download
- Just needed to get the next tool to work correctly
- For Export Only - Download
- This is what you will need to export your terrain file as a .bmp image for the next tool to be able to read and make displacements for you
- DispGen - Download
- This is the tool that will make your displacements and save a .vmf file for you to open and edit to your liking in Hammer.