F3D is a free and open source, cross platform (Windows, Mac and Linux) minimalistic 3D file viewer with a surprising number of features hidden below the surface. In addition to being able to display a variety of file formats (including glTF, STL, STEP, PLY, OBJ, FBX, Alembic and more), it is also capable of integrating into the Windows or Linux shell and generating 3D thumbnails of 3D objects.
One of the coolest features of F3D is the ability to raytrace your 3D model. Runnable from the command line, there are a ton of features including creating a transparent, raytraced and denoised image, with full control over camera position, HDRI environment mapping and more.
Details of F3D from the F3D homepage:
/fɛd/) is a fast and minimalist 3D viewer. It supports many file formats, from digital content to scientific datasets (including glTF, STL, STEP, PLY, OBJ, FBX, Alembic), can show animations and support thumbnails and many rendering and texturing options including real time physically based rendering and raytracing.
It is fully controllable from the command line and support configuration files. It can provide thumbnails, support interactive hotkeys, drag&drop and integration into file managers.
F3D is open source under the BSD-3 open source license with the code hosted on GitHub. In addition to the application, there is also a library for 3D model rendering.
You can learn more about F3D and see it in action in the video below.