is there a default way (from nativ eso) or a library to draw/render graphical (3D) objects into the world?
(I don't mean flat textures like the ability bar and so on)
I guess you will also need other libraries like LibGPS (maybe they are dependencies of these libs as well).
Addons like HarvestMap should use this lib to draw the textures (which afaik are 2d textures and just adjust so they look 3d for you if you move the mouse).