Part of the "Megastructures: The Visual Encyclopedia" book project, on sale now at https://www.kickstarter.com/projects/artofsoulburn/megastructures-the-visual-encyclopedia-book-project
A Krasnikov Tube is a permanent space warp created behind a spaceship as it travels at near lightspeed to some distant star system, and then uses the resulting tube for the return trip. The tube would provide a distortion of space such that it gets you back home shortly after you left. Painted in Photoshop, the main image uses no 3d, just various photos and hand painted elements. Will post a tutorial on the process in the near future.