Mobile 3D Graphics API

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The Mobile 3D Graphics API, commonly referred to as M3G, is a specification defining an API for writing Java programs that produce 3D computer graphics. It extends the capabilities of the Java Platform, Micro Edition, a version of the Java platform tailored for embedded devices such as mobile phones and PDAs. The object-oriented interface consists of 30 classes that can be used to draw complex animated three-dimensional scenes. M3G was developed under the Java Community Process as JSR 184. As of 2007, the current version of M3G is 1.1, but version 2.0 is in development as JSR 297.

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[edit] Goals of M3G

M3G was designed to meet the specific needs of mobile devices, which are constrained in terms of memory, memory bandwidth, and processing power, and which often lack an FPU and graphics acceleration hardware such as a GPU. The API's architecture allows it to be implemented completely in software or to take advantage of any acceleration hardware present on the device.

[edit] M3G is not Java 3D

M3G should not be mistaken for Java 3D, which extends the capabilities of the standard Java platform. Java 3D is designed for PCs that have more memory and greater processing power than mobile devices. M3G and Java 3D are two separate and incompatible APIs designed for different purposes.

[edit] Immediate and Retained Modes

M3G provides two ways for developers to draw 3D graphics: immediate mode and retained mode. In immediate mode, graphics commands are issued directly into the graphics pipeline and the rendering engine executes them immediately. When using this method, the developer must write code that specifically tells the rendering engine what to draw for each animation frame. A camera, and set of lights is also associated with the scene, but is not necessarily part of it. In immediate mode it is possible to display single objects, as well as entire scenes (or worlds, with a camera, lights, and background as parts of the scene).

Retained mode always uses a scene graph that links all geometric objects in the 3D world in a tree structure, and also specifies the camera, lights, and background. Higher-level information about each object — such as its geometric structure, position, and appearance — is retained from frame to frame.

[edit] Other Features

The M3G standard also specifies a file format for 3D model data, including animation data. This allows developers to create content on PCs that can be loaded by M3G on mobile devices.

[edit] Advantages and disadvantages of M3G

M3G is a high level 3D api that allows you to get results quickly. With only a few lines of code you can import a scene and animate it. The API is intuitive and has quite sophisticated features. The down side is that it is runs quite slow on a lot of mobile phones. This is mainly due to the fact that it uses floats and most mobile phones do not have a processor with a floating point unit. Nevertheless, the performance can be acceptable if you optimise your program correctly (especially on newer phones). Alternative proprietary APIs such as Mascot Capsule run faster (because of its use of fixed point calculations), but aren't as widely supported.

[edit] Further reading

  • Kari Pulli, Tomi Aarnio, Ville Miettinen, Kimmo Roimela, Jani Vaarala: Mobile 3D Graphics with OpenGL ES and M3G, Morgan Kaufmann, 2007, ISBN 0-12373-727-3
  • Claus Höfele: Mobile 3D Graphics: Learning 3D Graphics with the Java Micro Edition, Thomson Course Technology PTR, 2007, ISBN 1-59863-292-2
  • Carlos Morales, David Nelson: Mobile 3D Game Development: From Start to Market, Charles River Media, 2007, ISBN 1-58450-512-5

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