Some environment "sketches"

When I don't have a lot of time to make personal work, I try to make environment sketches, either drawn or in 3D.  They help keep me sharp, they let me practice and try new compositions and ways to handle textures and surfacing.  Here are a couple I've done in the last little while.

180818 Tundra Supplies1.jpg
180816 Alien Fungus1.jpg
180808 Abandoned Base1.jpg
180808 How Far Ill Go1.jpg
180805_Robot_at_the_River1.jpg
Land of 5000 lakes1.jpg
180804_Waste_Sunrise1_cinematic.jpg
180804_Industrial_Installation1.jpg
Mars_Approach1.jpg

What do you do to practice and keep yourself sharp?