Google's latest open source project is Lullaby, a collection of C++ libraries designed to help teams develop virtual and augmented reality experiences.

Built on an entity-component system architecture (ECS), Lullaby's goal is to provide an efficient, data-driven way to create, manipulate, and interact with objects in a "virtual" world.

Lullaby lists its full feature list as:

• High-performance C++ libraries designed for building VR/AR apps.
  
• Support for full 3D VR environments, including geometric worlds, panoramic images, and spatial audio.
  
• Entity-Component-System architecture for efficient runtime performance.
  
• Data-driven development tools for quick iteration.
  
• Common set of widgets (eg. images, labels, buttons, reticle, etc.) for UI development.
  
• Material VR: Widgets (eg. images, labels, buttons, reticle, etc.) for building VR UIs.
  
• Animation system for fluid, responsive UIs and "living" environmental objects.
  
• Support for Cardboard/Daydream headsets, Daydream VR Controller, and VR Keyboard.
  
• Java-based API for integration with existing Android applications.
  
• Used by multiple teams across Google incl: VR Home, Play Store, YouTube, Play Movies, and Earth.
  
• Multiplatform support: Android, iOS, Linux, and Windows.
  

You can learn more about Lullaby at the GitHub page: https://github.com/google/lullaby