Natural Selection 2 Developer Unknown Worlds is continuing to make good on its commitment to open development of its upcoming game Subnautica, releasing a playable demonstration of its new underwater environment technology as a free download on Steam (via unknownworlds.com):

The Subnautica Terrain Test is a tool that allows users to create procedural, underwater, semi-realistic terrain. A programmer can write a terrain generation algorithm, edit it, and see the terrain change in real time. It is available for free.

The Terrain Test is part of the development of Subnautica, an underwater open world exploration and construction game currently in development at Unknown Worlds. The test has several objectives:

• Allow anyone to create prototype terrain for Subnautica
  
• Get feedback on what kinds of terrain work best
  
• Explore the limits of procedural terrain generation algorithms
  
• Test performance and stability of Subnautica terrain rendering

Right now, the Terrain Test has full basic functionality. However, we will regularly update it through Steam to improve its ability to meet the above objectives. These updates will add new features (Such as Steamworks integration), functions (Such as stat tracking), and fixes (Let's be honest, not everyone will be able to run the Terrain Test perfectly, first go!)

When Unknown Worlds announced Subnautica last December, it described the ambitious game as a combination of sandbox, exploration, cinematic and role playing games, and not a genre that "has yet been invented".