Naughty Dog’s Michael Barclay launched a huge trend on Twitter that will give you a look at some early prototypes from AAA titles.
Blockouts are meant for studying the scale of an area and planning how the player will follow with his path. No details here, no textures, complex vegetation or other stuff. This stage is all about flexibility, so that developers can change elements. Developers can also use these early prototypes to test gameplay.
Here are some of the examples from Twitter: