CryEngine 3, originally called Sandbox Editor, is the current version of the level editor used to create levels for the CryEngine line of game engines by Crytek. The editing style is that of the sandbox concept, with the emphasis on large terrains and a free style of mission programming. The editor can also construct indoor settings.
The Sandbox's concentration on potentially huge (in theory, hundreds of square kilometers) terrain, means that it uses an algorithmic form of painting textures and objects onto the landscape. This uses various parameters to define the distribution of textures or types of vegetation.
This is intended to save time and make the editing of such large terrains feasible while maintaining the overall "real world" sandbox free roaming style. This is different from some editing styles that often use "fake backdrops" to give the illusion of large terrains.
You'll need some horsepower, but it does look great at High and Very High image quality settings.
The world is beautiful, teeming with things to do and places to explore. But let's have a look at PC graphics card performance.