Base class for Verge3D preloaders.
Does nothing, should be overridden in the subclass.
A callback which is called when the preloader is considered to be complete.
A callback which is continuously called during the loading process. The percentage parameter varies from 0 (0%) to 1 (100%).
The source code for this class is freely available in the src/extras/Preloader.js file inside the Verge3D's installation folder.
There is a built-in preloader that displays a logo with simple progress bar. See SimplePreloader class for more info.