I have spent a few months with SFML, and I now understand the library very well. I have wanted to learn OpenGL for some time now, so that I can further my knowledge of programming and understand what libraries are doing. Do you believe OpenGL would be a good learning experience? I would still use SFML, however I would also learn OpenGL as a side project.

I believe it'd be a great experience to write my own, smaller, graphics library with OpenGL after I've made a few games using the tool. It'd be fun, and I'd really understand the tool I was using. If I manage to create a library that is functional and useful, I might let other people use it, following in SFML's tracks.

What do you think? Would it be a good learning experience, or should I stick with SFML. And how long do you think it would take me (In years) to develop a nice, useful library for graphics?

Thank you for all responses (Even if there are none :)). Cheers :)!

Sure, learning a lower-level graphics API like OpenGL can be quite worthwhile. If you're interested, go for it. You can learn a lot, and that knowledge can be very useful. It's impossible to say how much of that knowledge you'll use; some people do more graphics programming than others, but the great thing about programming is that there's so much to explore, and it's all at your fingertips. Might as well experiment with it; who knows, it might lead you on a very enjoyable path (and if it doesn't, well, at least you learned what you don't want to do more of).

Just be prepared that it may take a lot of effort. OpenGL is low level, with lots of global states. If your are used to OO design, with flexible and how to design independent modules, you may be in for a unpleasant experience.

Also, you should now about Legacy OpenGL, and how to avoid it. Just to avoid getting a false start. I find Learning Modern 3D Graphics Programming an excellent tutorial. You can quickly skip what you already know, and concentrate on the essentials.