Thanks for your reply Zaoshi!!
So, its a good idea to write a 'wrapper' layer to graphics API if you want to write a cross platform game engine... right?
Someone who use Playstation SDK and/or some 'Nintendo SDK' may share some knowledge??
yeah, you want to have your own wrapper around the different graphics apis (libgcm for ps3, libgnm for ps4, dx11, dx for xbob, ogl, etc.)
Coming up with the right level of abstraction can take some time, you need to learn the differences in between the APIs pretty well to get it right, but overall not too difficult.
As Zaoshi mentioned, the constructs are pretty similar in between all major graphics apis. Some things are still a touch different such as constant management (gles2 vs dx11 /ogl3+ vs consoles), console graphics apis also usually expose alot more than is typically available on pc through dx and ogl.