I’ve posted this article for no more reason than to demonstrate one of the best and easiest to use browser-based 3D viewers available, not to mention an excellent resource of 3D models—Sketchfab. New features seem to be added at pace and there is an exciting feature (currently in alpha development) called MASSIVE, due in 2019. This enables the web player to show huge detailed models, for example, large geographic areas.
“MASSIVE uses a combination of data streaming and automated Level of Detail (LOD) mesh processing to make it possible to browse much larger 3D models in a browser.”
There’s a nice example of the implementation of this by Pix4d / Sketchfab MASSIVE, though note the detail and rendering is not fully developed as yet.
In the meantime, explore this nice model of Mars, by Thomas Flynn, as an example of the embedded web player.