Not all high-end applications are using OpenGL as their native 3-D graphics rendering API. Autodesk has developed its own 3-D rendering API called Heidi. Heidi is the low- level layer of HOOPS, a high-level 3-D API Autodesk owns as a result of acquiring Ithaca Software several years ago. HOOPS was once used by most of the CAD packages that didn't use OpenGL. Many of these packages have since been ported to OpenGL, as CAD companies have wanted to avoid having a competitor control their display capabilities.
Autodesk has debuted Heidi as part of its 3D Studio Max for Windows NT procluct, and has also indicated that Heidi will be the 3-D display and rendering engine used in a future release of its flagship product, AutoCAD. While some 3-D hardware companies are providing Heidi drivers, Autodesk has promised that Heidi will be able to sit on top of OpenGL.