Filament

Yes, Filament is released under the Apache 2.0 open-source license, which permits free commercial use, modification, and distribution. The engine is maintained by Google and hosted on GitHub under the google/filament repository. The Apache 2.0 license is one of the most permissive open-source licenses available, with no royalty requirements.

Filament supports Android, iOS, Windows, macOS, Linux, and WebGL, making it one of the few real-time PBR engines with broad cross-platform coverage from mobile to desktop. On Android it can render through both OpenGL ES and Vulkan backends, while on the web it uses WebGL 2. This breadth makes it suitable for applications that need consistent rendering quality across ecosystems.

Filament is written in C++ and exposes its primary API through C++, with additional bindings available for Java and Kotlin on Android. The engine also includes a material system that uses a custom shader language called matc for defining physically-based materials. Developers can integrate Filament into existing C++ engines or use it standalone via the provided Android library.

Filament is far more lightweight than Unity or Unreal Engine, focusing specifically on physically-based rendering for mobile and embedded platforms rather than providing a full game engine with physics, scripting, and asset pipelines. Its binary size is much smaller, which is critical for mobile app distribution. However, it lacks built-in tooling for game logic, scene editing, and physics simulation that full engines provide.