Chapter 15. A 3D Checkerboard: Checkers3D

Alternatives to Java 3D

There are a large number of ways of programming in 3D with Java without employing Java 3D. I've divided them into three categories: Java bindings to OpenGL, scene graph APIs, and game engine bindings.

Java Bindings to OpenGL

Several Java OpenGL bindings have been released over the years, but they tend to be incomplete, contain bugs, lack support and documentation, and often disappear suddenly. A (slightly out of date) list of Java bindings is maintained at the OpenGL site, http://www.opengl.org/resources/java/. It includes links to JOGL, LWJGL, Java 3D, GL4Java, and a few older projects. I'll describe only the active ones here.

GL4Java

GL4Java (http://gl4java.sourceforge.net/), known as "OpenGL for Java Technology," was one of the most popular OpenGL bindings until the arrival of JOGL. It can be used with AWT and Swing and has links to OpenGL 1.3 and vendor extensions.

Lightweight Java Game Library (LWJGL)

LWJGL (http://www.lwjgl.org/) utilizes OpenGL 1.5 with vendor extensions. It works with the latest versions of Java, so it can use the NIO and full-screen capabilities of J2SE 1.4. However, it doesn't support AWT or Swing. LWJGL is quite small, as the name suggests, so it is suitable for devices with limited resources.

The documentation for LWJGL is a little scanty though ports of the Nehe OpenGL tutorials have started to appear; they're at the end of the original Nehe tutorials (http://nehe.gamedev.net).

JOGL

JOGL (https://jogl.dev.java.net/) is the most recent of the Java bindings for OpenGL, and promoted by the Game Technologies Group at Sun. Like LWJGL, it supports the latest versions of Java, OpenGL, and extensions. It differs in being integrated with AWT and Swing, and it is considerably larger.

JOGL will be the starting point for the Java OpenGL reference binding being developed as part of Sun's JSR 231 specification process (http://www.jcp.org/en/jsr/detail?id=231). JSR 231 will become the official Java binding for OpenGL. A few details about its status as of December 2004 is at http://www.javagaming.org/cgi-bin/JGNetForums/YaBB.cgi?board=jogl;action=display;num=1102990415.

The amount of tutorial material on JOGL is growing. The JOGL Forum at java-gaming.org is a rich information source (http://www.javagaming.org/cgi-bin/JGNetForums/YaBB.cgi?board=jogl). One good JOGL introduction, by Gregory Pierce, can be found at http://www.javagaming.org/cgi-bin/JGNetForums/YaBB.cgi?board=jogl;action=display;num=1058027992. Another introductory article, "Jumping into JOGL," by Chris Adamson is at http://today.java.net/pub/a/today/2003/09/11/jogl2d.html.

The eBook Learning Java Bindings for OpenGL (JOGL) (Kagi) by Gene Davis is available from http://www.genedavissoftware.com/books/jogl/. It starts with basic JOGL examples, suitable for beginners. Several chapters and appendixes are free online.

All the Nehe OpenGL tutorials have been ported to JOGL and can be downloaded from http://nehe.gamedev.net or http://pepijn.fab4.be/nehe/.

JOGL's access to OpenGL and its extensions means it can utilize shading languages for special effects like fish eyes and spherization, and it can generate various types of shadow using textures. Java 3D 1.3.1. can mimic a few of these (see the section "Add-ons for gaming"), and Java 1.4 will include a shader language. A crucial difference is that JOGL employs program code to affect the graphics pipeline dynamically, whereas Java 3D mostly uses capability bits and get/set methods.

A posting to the Java Desktop 3D forum (http://www.javadesktop.org/forums/thread.jspa?threadID=3222) describes the use of JOGL's GLCanvas class to create a HUD (heads-up display) within a Java 3D application. The canvas can be manipulated in the pre- or post-rendering phases of Java 3D's immediate mode.

Scene Graph APIs

The creation of scene graph APIs for Java is something of a growth area, aided by the existence of lower-level OpenGL bindings. Most of the systems are open source.

Xith3D

Xith3D (http://xith.org) uses the same basic scene graph structure as Java 3D but can directly call OpenGL operations. This means it supports functionality like shadow volumes and vertex and fragment programs. This is the ideal situation for a 3D graphics API, making Xith3D a strong contender as an alternative to Java 3D.

Since the high-level APIs of Xith3D and Java 3D are similar, porting Java 3D code over to Xith3D is fairly straightforward. Versions of Xith3D run on top of JOGL or LWJGL.

A good tutorial for Xith3D beginners is at http://xith.org/tiki-index.php?page=Docs. There is a Xith3D forum at javagaming.org: http://www.javagaming.org/cgi-bin/JGNetForums/YaBB.cgi.

Two problems with Xith3D are its restriction to OpenGL (with no DirectX version), and the lack of scene graph thread safety.

OpenMind

The OpenMind API (http://sourceforge.net/projects/open-mind/) contains the expected elements, including hierarchical scene management and object transforms, dynamic cameras, lights, and fog. OpenMind is implemented on top of JOGL (it formerly used GL4Java).

jME graphics engine

jME (http://www.mojomonkeycoding.com/) was inspired by the scene graph engine described in 3D Game Engine Design (Morgan Kaufmann) by David H. Eberly (http://www.magic-software.com/Books.html). Currently, jME is built on top of LWJGL, with plans for JOGL support in the near future.

Jist3D

The alpha version of this engine will be released in 2005 (http://www.imilabs.com/). Many of its features are described in Practical Java Game Programming (Charles River Media) by Clingman, et al.

A key element of Jist3D is its utilization of JOGL, JOAL, and JInput. The rendering engine uses JOGL to support the scene graph and includes utilities for working with Java 3D graphs, a collision system, and 2D overlays.

JiD

JiD (http://javaisdoomed.sourceforge.net) includes loaders for Quake 2 MD2 and 3D Studio Max 3DS files. The implementation uses JOGL. The distribution includes Escape, a Doom-like game.

Aviatrix3D

Aviatrix3D (http://aviatrix3d.j3d.org/) is a retained-mode Java scene graph API above JOGL. Its tool set is aimed at data visualization rather than gaming and supports CAVEs, domes, and HMDs.

Kahlua

Kahlua (http://www.igd.fhg.de/CP/kahlua/) is a Java wrapper for Open Inventor (http://www.sgi.com/software/inventor/), a scene graph API available on the Unix/Linux and Windows platforms.

jFree-D2

jFree-D2 (http://sourceforge.net/projects/jfreed2/) is a reincarnation of the open source Java 3D implementation JFree-D, developed by Jean-Christophe Taveau in 1999. It provides a workable (but incomplete) implementation of Java 3D on top of GL4Java. Support for JOGL is planned in the future.

Game Engine Bindings

The following APIs emulate well-known game engines (e.g., Quake) or are Java wrappers around existing engines.

Auriga3D

Auriga3D (http://www.auriga3d.org/) works with Quake3 maps. There are versions on top of JOGL and LWJGL.

Jake2

Jake2 (http://www.bytonic.de/html/jake2.html) is a port of the GPL'd Quake2 game engine. It uses JOGL for the graphics and JOAL for the 3D sound. In tests, it achieves better than 85% of the speed of the original C:210 FPS compared to 245 FPS.

Ogre4J

Ogre4J (http://www.bytelords.de/cowiki/427.html) is a binding for the OGRE 3D Engine (http://www.ogre3d.org/) using JNI. OGRE 3D supports Direct3D and OpenGL and runs on all the main desktop platforms.

Jirr

Jirr (http://sourceforge.net/projects/jirr/) is a binding of the open source Irrlicht game engine (http://irrlicht.sourceforge.net/), which is written in C++. Jirr is in the early stages of development.

Odejava

Odejava (https://odejava.dev.java.net/) is a binding around the Open Dynamics Engine (ODE), an industrial quality library for simulating articulated rigid body dynamics. Typical applications include ground vehicles, legged creatures, and moving objects in VR environments. ODE is coded in C. The project contains tools for linking Odejava into Xith3D, OpenMind, and jME. A Java 3D binding is currently being developed as an offshoot of Project Looking Glass.