I love World Creator, especially the vegetation distribution pipeline. You can create some very realistic fields with it. Im going to check out impostors too - ive seen it a few times and wondered what it's about.
Stupid Rental. My Zbrush that I haven't paid for an update in years and is perpetual Trumps that on all counts.
Unreal Engine 4: Seasons Graduation Work
A graduation work for Digital Arts & Entertainment class created by youtuber nepfish. It features a small environment with changing seasons.