OpenGL plus plus

OpenGL++ was a graphics library written in C++ that supported object-oriented data structures on top of the OpenGL 3D graphics system. The project started as the result of a partnership between SGI, IBM and Intel (and later Digital Equipment Corporation as well) to provide a higher level API than the "bare metal" support of OpenGL, as well as being an implementation for Java3D. Work on OpenGL++ ended when SGI decided to partner with Microsoft instead, leading to the Fahrenheit project, which also died.

The vast majority of applications using 3D systems describe the objects in their "world" in a data structure known as a scene graph. A scene graph is normally organized as some sort of a tree data structure, with the nodes representing objects, and the edges their relationship to other objects in the world. For instance, a table might be represented by a single "table" object with several edges connecting its parts together, the table top, legs, etc. Key to high performance in 3D applications is deciding what objects in the world are actually visible given the current camera position and direction. For instance, objects behind the camera do not have to be drawn. Quick traversal of the scene graph is essential to making this "culling" operation occur quickly.

Scene graphs were generally left to the developer to implement, and it was all too common to see poor examples that led to poor performance. SGI had worked on a number of projects that were intended to help the developer produce a high-quality scene graph, but none of these had become widely used for a variety of reasons. Open Inventor was one such example, and was intended to simplify building the scene graph, but the results were not necessarily very high performance. OpenGL Performer was a similar project that was intended to produce high-speed scenes and support very large numbers of objects in the "world", but was not particularly easy to use.

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