BRL-CAD is a powerful cross-platform constructive solid geometry solid modeling system that includes an interactive geometry editor, ray-tracing for rendering & geometric analyses, network distributed framebuffer support, image & signal-processing tools.
PHIGS is an API standard for rendering 3D computer graphics. During the 1990's OpenGL became a more popular 3D API for professionals, and it still is today. PHIGS remains to be widely used in the film industry.
Open PHIGS uses OpenGL for rendering graphics rather than implementing it's own abstraction layer to the graphics hardware, or using the PHIGS Extension to X (PEX).
Open-source, cross-platform 3D rendering engine for .NET and Mono. The Axiom Engine is a high-performance C# port of the powerful OGRE engine and provides full support for DirectX, OpenGL and XNA on Windows, Linux, Android, iPhone and Windows Phone.