Valve's Free HTC Vive and Oculus Rift VR Creation Tool
On June 9th, Valve released their Virtual Reality world building tool. Titled Destinations Workshop Tools, the software allows you to build your in-game worlds using the Source 2 game engine -- the same tool used by Valve.
Destinations Workshop Tools is currently in early access. It's free and will remain that way when it is finished. With the community's help in guiding the development, it may see additional features on release. The VR worlds would be optimized for the HTC Vive and the Oculus Rift.
In order to experience what your create in the Destination Workshop Tools it will be necessary to have a virtual reality device. The device does not to be one of the devices listed above. Any headset that is supported by OpenVR will work. The input devices you can allow access to are tracked motion controllers and your standard gamepad. You can also create the worlds for seated or standing use, or even a room scale environment.
For VR enthusiasts and designers, the Destinations Workshop Tools is a great way to step into world building for games. With wiki resources available, the learning curve isn't very high. And, with a community building around the program since its release, you can explore other creations through Steam.