Can you make a GUI with opengl?

Yes absolutely. Maybe not practical though. Have a look at github.com/ocornut/imgui you can use opengl to render the GUI.

Which graphics API should I learn?

You should be learning OpenGL first, as that is the standard for Graphics, across so many platforms. Even if there is a newer library, understanding the basics, and working with a language that is used all over the industry, is very important… Especially since Vulkan wont be used in Big Companies for awhile, since.

What looks better Vulkan or OpenGL?

Vulkan targets high-performance real-time 3D graphics applications, such as video games and interactive media. In contrast to the older OpenGL and Direct3D 11 APIs, Vulkan is intended to offer higher performance and more balanced CPU and GPU usage.

Are there any alternatives to OpenGL for GUI apps?

No, they are almost exclusively used for games. Normal GUI apps use Cocoa on Mac or Windows API on Windows. They are poorer in features, but they are WAY easier to use than OpenGL or DirectX is.

Do UI developers use DirectX or OpenGL?

Most of the UI frameworks are wrappers around OpenGL and DirectX, or atleast uses simpler frameworks like GDI+. So most of the client side developers don’t directly call DirectX or OpenGL API, instead they just call UI frameworks which underneath call OpenGL or DirectX. For example WPF in .net is using Direct 3D to render 2d surfaces.

What is OpenGL and how does it work?

OpenGL is mainly considered an API (an Application Programming Interface) that provides us with a large set of functions that we can use to manipulate graphics and images. However, OpenGL by itself is not an API, but merely a specification, developed and maintained by the Khronos Group .

How much does it cost to learn OpenGL?

Learn OpenGL is free, and will always be free, for anyone who wants to start with graphics programming. All content is available here at the menu to your left. Simply hit the Introduction button and you’re ready to start your journey!