Filament
Google's open C++ renderer covering PBR materials, lighting, post effects, asset conversion, and multiple graphics backends.
Why use it
Applications and custom engines needing high-quality embedded rendering can reuse it without adopting a full editor.
Where it fits
Find engines, frameworks, code libraries, version control, and production automation.
What to check
Scene tools, gameplay systems, and authoring workflows are separate, and platform integration requires native skills.