- Java SE Development Kit (JDK) (Java 3D uses the JDK)
- Java 3D (The most recent version is on top of the page.)
Download PSDL Viewer on fre_ber's website: https://mm2.apan.is-a-geek.com.
PSDL Viewer is a must if you want to make full featured cities for MM2. If you have questions about the program, just make a thread here. I'm very active using the program at the moment.
If you are new to PSDL Viewer and want to learn making cities with it, I suggest you to read all the documentation in this thread: City Editing Gems. That's what I did.
Fre_ber also made MM2 Kiwi and has some useful documentation on it and an MM2 file tree.