Cross-platform, graphics API agnostic, "Bring Your Own Engine/Framework" style rendering library.
TiXL is an open source software to create realtime motion graphics.
The DirectX Tool Kit (aka DirectXTK) is a collection of helper classes for writing DirectX 11.x code in C++
DirectXTex texture processing library
C++ 3D Game Tutorial Series (DirectX) - Learn to code a DirectX 3D Game in C++ from scratch
Lightweight Game Engine/Framework in C++17 with WYSIWYG Editor. Experimental C# bindings.
DirectXMesh geometry processing library
A modern cross-platform low-level graphics API
ClassicUO - an open source implementation of the Ultima Online Classic Client.