3D Viewer is described as 'A secure, private 3D viewer for Google Drive to view, organize, and comment on Rhino (.3dm), STEP, STL, and OBJ files directly in the browser without downloading' and is a 3D Modeler in the photos & graphics category. There are more than 10 alternatives to 3D Viewer for a variety of platforms, including Web-based, Windows, Mac, SaaS and Linux apps. The best 3D Viewer alternative is Verge3D. It's not free, so if you're looking for a free alternative, you could try Sketchfab or Vectary. Other great apps like 3D Viewer are Lumion, glbee, STP Viewer and A360 VIEWER.