Open PHIGS
PHIGS (Programmer's Hierarchical Interactive Graphics System)
...The reason for doing so is that today every graphics card manufacturer provides their own OpenGL implementation, which takes full advantage of the accelerated drawing capabilities in the hardware.
PHIGS is a higher level API than OpenGL that works with a hierarchical scene graph. Models are built up in a Centralized Structure Store (CSS), a database containing the drawing primitives and their attributes (color, line style, etc.). CSSes cand be shared among a number of views, known under PHIGS as a workstation.
PHIGS is defined by the ISO standards ISO/IEC 9592 & 9593. Open PHIGS provides a library for C.