RenderDoc is a free MIT licensed stand-alone graphics debugger that allows quick and easy single-frame capture and detailed introspection of any application using Vulkan, D3D11, OpenGL & OpenGL ES or D3D12 across Windows 7 - 10, Linux, or Android.
devoted to game / 3D graphics programming with DirectX / OpenGL using C++. Contains downloadable source code for several small and very specific sample programs that I think will be very helpful to anyone trying to learn both 2D and 3D game programming.
a game programming library for C/C++ developers distributed freely, supporting the following platforms: DOS, Unix (Linux, FreeBSD, Irix, Solaris, Darwin), Windows, QNX, BeOS and MacOS X. It provides many functions for graphics, sounds, player input, etc..
a free / freeware open source tool for 2-D game development. It is designed for the Windows 9x/DirectX platform, and targeted at people spanning a range of skill levels.
Hardware accelerated 2D full featured middleware for all who want to develop commercial quality 2D games rapidly and easily. It covers all imaginable 2D game genres (DirectX)
open source high performance realtime 3D engine written and usable in C++ and also available for .NET languages. It is completely cross-platform, using D3D, OpenGL and its own software renderer.