Java OpenGL - Design

Design

The base OpenGL C API, as well as its associated Windowing API, are accessed in JOGL via Java Native Interface (JNI) calls. As such, the underlying system must support OpenGL for JOGL to work.

JOGL differs from some other Java OpenGL wrapper libraries in that it merely exposes the procedural OpenGL API via methods on a few classes, rather than trying to map OpenGL functionality onto the object-oriented programming paradigm. Indeed, most of the JOGL code is autogenerated from the OpenGL C header files via a conversion tool named GlueGen, which was programmed specifically to facilitate the creation of JOGL.

This design decision has both its advantages and disadvantages. The procedural and state machine nature of OpenGL is inconsistent with the typical method of programming under Java, which is bothersome to many programmers. However, the straightforward mapping of the OpenGL C API to Java methods makes conversion of existing C applications and example code much simpler. The thin layer of abstraction provided by JOGL makes runtime execution quite efficient, but accordingly is more difficult to code compared to higher-level abstraction libraries like Java3D. Because most of the code is autogenerated, changes to OpenGL can be rapidly added to JOGL.