Awesome! I had been working on a similar project couldn't figure out the snow on the trees for the life of me! It's great to see how you approached it. The work look great! Thanks for sharing your process.
I believe author would be surprised that it's not american, but soviet bunker :)
Houdini is now one of the top tools when it comes to generating huge open worlds for games. Just check a couple of our articles on Ghost Recon: Wildlands (here and there) or this one on Horizon Zero Dawn to learn about the tool’s possibilities. Do you want to know more? SideFX has shared a recording of a session by Paul Ambrosiussen from GDC 2018 that shows how you can mix Houdini and game development. Actually, the tool is all about creative freedom, not about technical nightmares.
In this presentation, Paul will demonstrate that Houdini for Game Development is NOT hard! by featuring some of the ways Game Development Tools simplify your workflow. Using the complimentary toolset in Houdini will enable you to focus on building high-quality creative experiences, rather than technical nightmares file I/O might bring with them.
Make sure to check out the Go Procedural channel on Vimeo for more Houdini videos.