Khronos Group

The Khronos Group publishes interoperability specifications for graphics and related computational interfaces. Its OpenGL specification defines a rendering pipeline, including rasterization, fragment shaders and per-fragment operations. A specification makes observable behavior portable across implementations: for example, a configured depth buffer comparison determines whether a candidate surface contributes to the framebuffer. This is a definition of an interface contract, rather than a requirement that all implementations use identical internal hardware.^[ref][ref]