If You’re Android Graphic Programmer, Check Out Google Filament

Filament is a PBR (physically based rendering) engine optimized for Android, but also works on Linux, macOS and Windows.

Filament is a tool made for Android developers who want to create high quality 2D and 3D rendering with ease. Filament features Native C++/Java/JNI API, OpenGL, Vulkan 1.0, HDR, Physical light units, MSAA and more. And they also support in-depth documents for Developers.

For more info: Download / PBR Guide / Material GuideMaterial reference sheet