Instant Terra:
http://www.wysilab.com/index.html#terrainstant
What’s Instant Terra?
Dedicated to the video game industry, CGI and VFX studios, Instant Terra is a 3D terrain creation software that will boost your productivity and creativity.
Based on innovative technologies, Instant Terra offers unique advantages:
Unlimited size and resolution: Do not let your computer determine the maximum size of your terrain. Your terrain can contain billions of quads. Instant Terra supports it while remaining fluid.
Full-screen, real-time preview: Change a setting and immediately see the result. No preview window: the result is already visible in your main window.
Ultra-fast generation: Your terrain is ready and now you want to use it for the rest of your production. Instant Terra generates it much quicker than existing solutions.