Criticisms of Java 3D for Games Programming

Java 3D Strengths

The core strengths of Java 3D are its scene graph, its performance, collection of unique features, the fact that it's Java and can call upon an enormous number of support packages and APIs, and its extensive documentation and examples.

The Scene Graph

The scene graph has two main advantages: it simplifies 3D programming and accelerates the resulting code. The scene graph hides low-level 3D graphics elements and allows the programmer to manage and organize a 3D scene. A scene graph supports many complex graphical elements.

At the Java 3D implementation level, the scene graph is used to group shapes with common properties, carry out view culling, occlusion culling, level of detail selection, execution culling, and behavior pruning, all optimizations that must be coded directly by the programmer in lower-level APIs. Java 3D utilizes Java's multithreading to carry out parallel graph traversal and rendering, both useful optimizations.

Performance

Java 3D is designed with performance in mind, which it achieves at the high level by scene graph optimizations and at the low level by being built on top of OpenGL or DirectX Graphics.

Some programmer-specified scene graph optimizations are available through capability bits, which state what operations can/cannot be carried out at runtime (e.g., prohibiting a shape from moving). Java 3D also permits the programmer to bypass the scene graph, either totally by means of an immediate mode, or partially via the mixed mode. Immediate mode gives the programmer greater control over rendering and scene management, but it isn't often required. Retained mode programs only use the scene graph API. All the examples in this book employ retained mode.

Unique Features

Java 3D's view model separates the virtual and physical worlds through the ViewPlatform and View nodes. This makes it straightforward to reconfigure an application to utilize many output devices, from a monitor, to stereo glasses, to CAVEs.

Virtual world behavior is coded with Behavior nodes in the scene graph and is triggered by events. Among other things, this offers a different style of animation based on responding to events instead of the usual update redraw/cycle you've seen in all my 2D games programs.

The core Java 3D API package, javax.media.j3d, supports basic polygons and triangles within a scene graph; the com.sun.j3d packages add a range of utility classes including ColorCube and SimpleUniverse, mouse and keyboard navigation behaviors, audio device handling, and loaders for several 3D file formats.

Geometry compression is possible, often reducing size by an order of magnitude. When this is combined with Java's NIO and networking, it facilitates the ready transfer of large quantities of data between applications such as multiplayer games.

Java 3D allows 2D and 3D audio output, ambient and spatialized sound. Unfortunately, the sound system has bugs. Consequently, spatialized sound isn't available by default in Java 3D 1.3.2. Version 1.4 may offer a JOALMixer class instead, i.e., a JOAL-based audio device. JOAL is a Java binding for a 3D audio API called OpenAL, which is supported by many sound cards.

Java Integration

Java 3D is Java and offers object orientation (classes, inheritance, polymorphism), threads, exception handling, and more. Java 3D can easily make use of other Java APIs, such as JMF and JAI. The Java Media Framework (JMF) includes mechanisms for playing audio and video segments and can be extended to support new forms or audio and video (http://java.sun.com/products/java-media/jmf). Java Advanced Imaging (JAI) provides many advanced image processing features, including over 100 imaging operators, tiling of large images, network-based capabilities, and the means to add new image processing features (http://java.sun.com/products/java-media/jai).

Documentation and Examples

The Java 3D distribution comes with about 40 small to medium examples. They're a great help but somewhat lacking in documentation. Fortunately, more resources are online. Sun's Java 3D tutorial is available at http://java.sun.com/products/java-media/3D/collateral/. The tutorial is a good introduction to Java 3D but can confuse beginners. Ben Moxon has a good introductory Java 3D tutorial based around getting a MilkShape 3D figure to move over a hilly terrain (http://www.newview.co.uk/e/tutorials/java3d/index.jsp) and is called The Little Purple Dude Walks.

Reading Up

I recommend three Java 3D textbooks as supplemental reading:

• Java 3D API Jump-Start by Aaron E. Walsh and Doug Gehringer (Prentice Hall)

• Java 3D Programming by Daniel Selman (Manning)

• Java Media APIs: Cross-Platform Imaging, Media, and Visualization by Alejandro Terrazas, John Ostuni, and Michael Barlow (Sams)

The Walsh and Gehringer text is an excellent overview, using code snippets rather than pages of listings. It complements the Java 3D tutorial.

The Selman book is more advanced. For the games enthusiast, Selman describes a Doom-like world, utilizing first-person perspective keyboard navigation and scene creation from a 2D map. The world contains bookcases, pools of water, flaming torches, and animated guards.

Terrazas is involved in VR research and business, so there's a heavy slant in the 3D part of his book toward less common topics such as sensors, head tracking, and a bit on CAVEs. There's an example combining Java 3D and JMF to create a streaming 3D chat room.