OpenGL Essential Links
OpenGL man pages and reference cards
Download and print the references cards, and bookmark the man pages. You will need them.
Official OpenGL specification by version and extension description.
Contains an often updated collection of samples for OpenGL features.
OpenGL Pipeline Map
Lost in the OpenGL pipeline? Here is a map.
OpenGL Hardware Matrix
What is supported and where.
Example-based exploration of the OpenGL API. 7th edition covers OpenGL 4.5. Code samples available.
Collection of articles presenting advanced OpenGL or OpenGL-based techniques.
OpenGL Online Tutorials
Beginner and intermediate level tutorials.
Another set of very well made tutorials
The definitive real-time rendering reference. The website is also quite helpful.
The ultimate book on the subject.
Libraries and tools
The OpenGL friendly math library used for these tutorials.
A compact multiplatform windowing toolkit used for these tutorials.
A geometry importer library supporting a wide array of formats.
dear imgui (AKA ImGui), is a bloat-free graphical user interface library for C++. It outputs vertex buffers that you can render in your 3D-pipeline enabled application