Open PHIGS
PHIGS (Programmer's Hierarchical Interactive Graphics System)
... 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.